Knife blade materials

This page collects work comparing various knives to summarize the information gathered on blade materials and as well provide additional reference links on material properties.

Composition, name and heat treating information : main

Composition tables/information :

Tool steel name cross reference information :

Heat treating :

Maker commentary :

Materials information :

Carbon and alloy steels

Steels discussed :

Steel Carbon Manganese Chromium Nickel Vanadium Copper Molybdenum Silicon HRC
1084 0.84 0.75 45-66
1095 0.9-1.03 0.3-0.5 45-66
52100 0.98-1.10 0.25-0.45 1.3-1.6 58-62
50100-B 0.93 0.43 0.60 0.03 0.21 0.16 0.24 56-61

The specifications for 52100-B is the composition of an individual blade.

1084 : main

Nominal composition of 1084 :

Note 1084 is a carbon steel which has a specific definition :

Carbon steels are regarded as steels containing not more than 05% manganese and 05% silicon, all other steels being regarded as alloy steels

The first thing that is obvious is that this is a high carbon steel. Looking at the diagram to the right, 1084 has much more carbon than is necessary even for full hardness in steels. The extra carbon which isn't dissolved in the martensite is used to form cememtite, or iron carbide, which increases the wear resistance over a steel such as 1060 which could obtain similar hardness.

The other thing which is obvious is that it only has a small amount of alloying elements which increase hardenability and so it will require a very fast quench, either water or a very fast oil.

Note in the isothermal transformation diagrams to the right how the small amount of Chromium and the much larger amount of Manganese in O1 (just under 1.5%) makes a severe impact on the hardenability.

The O1 shows a severe weakening or suppression of the diffusion based transformations (pearlite) during the cooling and thus can take a much slower quench. This reduces issues of warping and quench cracking which is why slower quenching steels can be favored by makers/manufacturers.

Note that in addition to Carbon and Manganese, 1084 will typically contain Silicon, Phorphorus and Sulphur. The last two are impurities and are present in all steels, Silicon will in general as well as it is commonly used as a deoxidizer and will be present in the original ore.

Silicon does serve as an alloying element in steels as it dissolves in ferrite and strengthens it. It also enhances corrosion resistance, commonly used in austenetic stainless steels. It is also very significant in regards to its effect on carbide formation as it suppresses it both during the quench and during tempering. However in order for these effects of silicon to be significant, they require more substantial amounts than what is typically found in 1084.

In regards to the carbon content of 1084, it is very close to the eutectoid point for the iron/carbon system whihc is ~0.77%. This is a fairly technical point but has some implications for the knife maker.

As noted in the diagram on the right, a steel close to the Eutectoid point will, upon heating, transform from from ferrite+pearlite to pure austenite. Steels which have a lower carbon content will transform to austenite but will still contain ferrite and steels which have a higher carbon content will contain cementite instead of the ferrite.

Again, this is a technical point, but it is of interest to those hardening the steel.

In regards to the actual properties of 1084, it will have physical properties similar to other carbon and low alloy steels. Often times much argument will be made about small changes in steels which imply large differences but the metallurgical data doesn't reflect such extravagant claims. For example, it is true that in general 1095 will have a slightly higher amount of cementite than 1084 which will give it a higher wear resistance, but how much is likely not to be significant. In some detail, from research looking at the wear on steels in grinding ore, here are the relative wear rates of 1040 carbon steel vs 1090 carbon steel : 1

Note that this is comparing a very large difference in carbon content, from 0.4 to 0.9%, much larger than say 1084 vs 1095 and yet the wear factors of the tooling change by less than 10%.

If this seems odd then realize that the volume of cementite (iron carbide) in these pure carbon steels is relatively small. For example the picture on the right is of DIN 12206 which is a 1.5% carbon steel. Even in this much higher carbon content there is still only approximately 5% of carbide by volume of the steel.

As the carbon content drops so does the volume of carbide. In steels such as 1084 or 1095, the carbide volume will only be a couple of percent. Comparing something like 1084 vs 1095 then in regards to wear resistance is talking about a very small fraction of a percent difference in carbide volume. If the other aspects of the steels are similar, which are strongly influenced by the initial steel quality and the heat treatment, the performance of 1084 vs 1095 is likely to be near identical.

What is the significant difference then in 1084 vs the lower carbon content steels such as 1045 or similar alloys such as 4340? The critical aspect is the toughness and in particular the ductile to brittle transition. This is important in steels as it is the temperature at which steels will fail in a brittle mode vs a ductile one. This means that they will crack with little or no deformation.

In high carbon steels, the ductile to brittle failure point is actually at high temperatures, above room temperature which means that when fully hardened they tend to break when over stressed with little deformation and crack cleanly. It also means that the amount of energy they absorb is severely reduced. However as noted in the figure in the right, the low to mid carbon steels have a ductile to brittle temperature which is below zero which means they are more suitable for impacts and harsh work in colder weather.

Knives used in 1084 :

The bush knife from Takach forge was a solid example of 1084. It could easily do extended wood work and suffer no significant fracture. It was hard enough to also resist rolling and tended to blunt by slow wear. As this is a low carbide steel with only a small volume of cementite and no alloy carbide it ground very easily even on natural stones. As it has a decent working hardness and quality hardening from the maker, it also sharpens easily to a fine finish and has no significant issues with burr formation.

1095 : main

Nominal composition of 1095 :

1095 is a very high carbon steel steel. The carbon content allows it not only to reach maximum hardness in martensite, it has excess carbon to form a significant volume of cementite. This gives it a significant advantage in abrasive wear resistance over the medium carbon steels in which all of the carbon typically is utilized in hardening the martensite.

As 1095 has a very restricted alloy content, it has a very low hardenability as it does not contain significant amounts of elements to increase hardenability :

and only has a small amount of Mangenese. Note in order to get a full oil hardening steel the Mangenese content has to be much higher as seen in O1 for example at 1.0 - 1.4% .

However as knives are generally made from very thin sections of steels then the shallow hardening isn't a critical concern and fast quenching oils are commonly used to harden 1095.

In regards to properties, as 1095 also has no alloy content which effects tempering :

It softens continuously as the tempering temperature is raised and there is a smooth loss of hardness and strength.

Note that 1095 is subject to TME (tempered martensite embrittlement) with tempering temperatures in the neighborhood of 500F even though it doesn't consistently show up on charpy/izod impact tests. However it does show up on torsional impact/ductility measurements which has to do with the axiality dependence of TME due to cementite precipitation.

Knives personally used in 1095 :

The Ontario machetes had suffered gross damage losing large pieces out of the edge on hard woods. The Ontario Spec Plus knives, also had problems; one blade was too brittle, another had an unhardened tang, and one was even ground the wrong way, the edge was thicker than the spine. The Ontario RTAK also took severe damage clipping off branch stubs .

The Livesay RCM also deformed during limbing though not as severe as the Ontario's. The custom RTAK from Livesay did not have such a problem and the performance was solid for a wood cutting tool.

The TOPS Steel Eagle also had several problem in regards to brittle fracture. The teeth cracked when used as wire breakers and the tip and edge cracked when digging an arrow head out of a piece of wood ref. It also had reduced slicing edge retention compared to a Battle Mistress in INFI on carpet and wood.

The narrow Mora had problems with brittle tip fracture on light work and in general the edge retention was low on hemp and carpet.

The custom paring knife was heat treated to maximize torsional toughness and give a very high torsional strength and ductility and compressional strength. The edge had a very thin profile and a very acute grind yet was still able to cut woods, bone and even sod with no significant damage. The edge holding in general was also very high on both hemp and carpet.

Summary : 1095 is a plain carbon steel which offers a very high working hardness, moderate wear resistance, and very high apex stability. It can also be tempered for high toughness by drawing above the TME point around 500F. Unfortunately it is often used in very inexpensive and low quality knives and therefore it often has very low performance and issues with durability.

52100 : main

Nominal composition of 52100 :

52100 is a high carbon steel, the carbon content is well beyond what is necessary to reach maximum hardness in martensite and thus it will have a small amount of excess carbide both in the forms of cementite (iron carbide) and chromium carbide. This will give it an advantage in wear based properties over the mid carbon steels which lack the abundance of carbon to both fully harden the martensite and have a surplus to form cementite. This difference is pretty dramatic on standard materials testing, for example using ASTM G65 (200/300 mesh sand/silica) 52100 has almost a 2.5:1 advantage over 1040 :

-5% NaCl quench, 200C temper - 1040 : weight loss = 0.17 grams

-5% NaCl quench, 200C temper - 52100 : weight loss = 0.07 grams

The advantage, though not as drastic holds for the high carbon steels due to the small amount of chromium carbides in 52100 :

At a hardness of HRC = 61, 52100 steel has a better cutting performance than 1086 steel and both are generally better than Damascus steel.

Note in the above Verhoeven is referring to a higher CATRA score, which is a measure of edge retention cutting abrasive paper, when he notes "cutting performance". The same work also shows AEB-L to have slightly improved performance again in the same check for the same reason, a slightly higher volume of chromium carbides.

Aside from wear resistance though carbides, the Manganese and Chromium in 52100 also significantly increase the hardenability over a plain carbon steel such as 1084 or 1095. Both of these elements do this in slightly different ways.

The chromium in the steel increases the hardenability by reducing the high temperature diffusion reactions. As the blade cools, the Chromium slows the formation of pearlite. The manganese addition has a similar effect, it also reduces the formation of pearlite, but it does by expanding the austenite phase to being stable (existing) lower temperatures. This ideally prevents the ferrite from forming until ideally the temperature has been reduced by the quench to the point martensite starts to form.

Note how 52100 compares well to O1 in regards to hardening response as it has increased Chromium but reduced Magnesium and the balance gives a similar suppression of diffusion reactions.

As 52100 is a common industrial bearing steel there is a wealth of data on how it performs as such compared to other bearing steels which show among other things : 52100,S90,440C,REX20

And the heat treatment of it has been studied in detail to determine for example how to minimize the retained austenite and maximize the hardness :

The experiments conducted show that austenitizing and tempering temperatures have the most influence on the retained austenite and the hardness in the heat treatment of 52100 steel. The austenitizing and tempering temperatures of 827C and 177C, respectively, gave the lowest austenite and highest hardness values for both the second and final Taguchi analyses, indicating that no further refinement of the experiment is necessary.

Note that critical in the heat treatment of 52100 is to adjust the soak time and temperature so that enough carbon gets dissolved in the austenite to achieve full hardness, but just that amount. As noted in the above, the hardness tends to maximize at approximately 0.6% of carbon dissolved in the austenite and raising above this tends to increase the retained austenite, promote plate (vs lathe) martensite and reduce wear resistance by dissolve more of the chromium carbide.

52100 has also been extensively studied in regards to the properties of bainite and duplex bainite+martensite structures :

Bainite + martensite duplex microstructures can be produced in AISI 52100 steel via combination of austempering and quenching processes.

Bainite + martensite duplex microstructure yields in high levels of hardness (55-64 HRc) and enhanced impact toughness (24-54 Joule).

In that work it is clearly shown how optomizing the microstructure allows an increase in toughness of almost three fold with a small loss of hardness from 61 to 59 HRC by adjusting the austempering time at temperature from 15 to 30 minutes. However while standard bainite does have increased toughness over martensite, the opposite is true in regards to wear resistance :

Austempered samples have highest impact strength, the least being martempered samples. The impact strength increased with soaking time in austempered samples up to certain level. 20% improvement is observed with austempering process.(iii)

Annealed samples have the highest wear, while martempered samples have the least wear. Approximately 50-60% wear resistance is increased with martempering process.

Now 52100 can't be discussed in regards to knives without talking about the grain structure. To start, there is much confusion in the industry where both the austenite grain boundaries and the primary carbides are both referred to as grain size which is misleading. It is very necessary to separate them as they have completely different effects in steels.

It is known that a reduced grain size strengthens steels and can do so significant as calculated by the Hall-Petch equation which shows an increase in yield strength (in ferrite) which increases as the inverse of the square root of the grain size. However a strong concern as a result of the reduction in grain size is a corresponding reduction in hardenability.

Martensitic transformation in an ultrafine-grained (UFG) steel was investigated. The UFG steel was a plain carbon steel containing 1.0 wt.% C and prepared by thermomechanical treatment. The grain size was approximately 1 m. The sample was reheated at 1023 K for 5 min and then cooled in water to conduct a martensitic transformation. In addition to martensite, lamellar pearlite was observed in microstructure. When the heating time was prolonged to 7min, after quenching process, matensite was only observed. The results indicate that when heating time is shorter, the grain size is small (2.5 m) and lamellar pearlite can be formed as quickly as martensitic transformation in quenching process. When the heating time is prolonged, grains grow (4 m) and no lamellar pearlite is observed. This phenomenon is greatly related the increasing resistance for martensitic transformation and accelerated diffusion of carbon atoms due to the refinement of grains in the steel

In short, a 1% C steel (1095) had ultra-fine grain (15 ASTM) and when it was water quenched it formed a significant amount of pearlite due to the very fine grain. In order to get full martensite with a water quench, the grain had to be coarsened to increase hardenability. Beyond 12-13 ASTM then water isn't a sufficient quenchant for 1% carbon steels. This fact has become known to some knifemakers who have had to resort to accelerated quenches in order to preserve full hardness when the grain size was reduced through thermal cycling, using water on 52100 for example or even brine or "super quench".

Knives personally used in 52100 :

The Blackjack small was used for a lot of work, in regards to edge retention it was behind S30V and 10V in slicing cardboard with various edge finishes South Fork Review.

Ray Kirk's test blades were made from 1084, L6, 52100 and D2 at various hardness levels, which were used unmarked so the steel types were unknown until after the work was completed to examine sharpness and edge retention on used mats, as well as ease of sharpening and durability by cutting bone and concrete. At high sharpening angles (20 degrees) there was no difference in initial sharpness. In edge retention on the used mats the D2 blade consistently outlasted the 52100 knife on the mat cutting which out cut the other two steels. On the bone cutting the L6 blade fared the worst due to the low hardness. On the concrete cutting the 52100 blade had the best balance of strength and durability to minimize damage. While there was a large difference in machinability, the blades which sharpened the fastest tended to be just the ones which suffered the least damage or wear in use, so either D2 or 52100 depending on what was cut.

Ray's ABS bowie was used for a lot of wood work and rope cutting and found to have lower edge retention than a straight handled Battle Mistress (INFI) on cutting used poly, however the edge angles was lower on Ray's knife and it still cut significantly better even when the edge was degraded. The bowie was also subjected to both light and hard impacts off of a concrete block and it did well taking only minimal edge damage inspite of its very acute edge profile, and was much more durable than a tactical knife from Strider in a much thicker edge profile.

The MEUK in 52100 was several blades on used carpet and it had significantly better edge retention than a Swiss Army knife, a custom in LM1 and another 52100 blade by Ed Fowler though was behind another custom in CPM-10V. The MEUK was also behind S30V and 10V several high alloy steels slicing carpet. One of the main drawbacks to 52100 is the low corrosion resistance, and this was evident with the MEUK which would developed a patina quickly in the kitchen on acid foods.

Ed Fowler's Pronghorn was used for a lot of work include cutting hemp where at best it matched the performance of an Opinel. On used carpet it did poorly, being outperformed by a Swiss Army knife. On lateral loads it did very poorly showing little flexibility and taking a set immediately and being very easy to bend, acting essentially like unhardned steel. However this blade was hardness tested and found to have a very low hardness, less than 40 HRC.

Summary : 52100 tended to show what would be expected from the materials properties, that it is behind higher carbide steels such as S30V on abrasive cutting, but it has superior grindability, toughness, and ease of sharpening.

50100-B / 0170-6C / Carbon V: main

This is one of the more common carbon steels in the cutlery industry, however it is rarely called by that name. Cold Steel calls it Carbon V, Camillus calls it 0170-6C, and Case calls it "chrome vanadium", W7 is tool steel with a similar composition.

Knives personally used in 0170-6C / Carbon V :

The Twistmaster was used for a lot of hemp rope cutting and with a fine ceramic finish at 22 degrees per side it had only a fraction of the edge retention of a D2 custom from Mel Sorg at 62 HRC. With the edge sharpened to a fine diamond finish at the same angle, it was identical to the Becker CU/7 once the edge had been reprofiled to a similar level of cutting ability by adjusting the angle which makes sense as they are the same steel at the same hardness. It was however significantly behind higher and harder alloy steels such as VG-10 and D2.

The Machax was used for a lot of wood work compared to multiple large blades, the edge retention was much lower than the Busse Battle Mistress. The Machax took edge damage in the form of chips and dents cutting hard woods with the stock profile. With the edge angle reduced the damage was much reduced but the edge retention was much lower than on the Battle Mistress as the edge would lose slicing aggression much faster. The Machax was also given a soak in salt water and as expected the blade formed surface rust readily but didn't tend to pit.

The Patrol Machete was used on a variety of light vegetation where it did well, however it took gross damage on light limbing. A replacement suffered extensive edge damage on the same work and then cracked easily with a few light slap on a log. While the edge was too thin which can be used to argue for the rippling, there was gross fracture under far too low a level of stress.

The Becker CU/7, similar to the Twistmaster, also had a large disadvantage compared to the Sorg Custom, this time the comparisons was at a very rough finish, left by a 100 grit aluminum oxide belt. The Becker was not even in the same class. With a much reduced edge profile the CU/7 was subjected to very hard impacts, the edge fractured readily, but there was no gross damage up into the primary grind as seen for example with the WB from Strider.

The Combat Bowie was used for some bone chopping compared to the Camp Tramp in SR101 and had a slight advantage after a short round of bone cutting with both blades at similar angles and finishes. However the much higher chopping ability of the Becker would give it an advantage and in general this type of work needs to be repeated to insure that it isn't just bone variance or a bad swing. However it would be reasonable to conclude the edge durability is at least similar in class.

Overview : This steel is one of the most common production grade cutlery steels, called different names by different manufacturers. It is basically a low alloy enhancement of 1095 designed to give deeper hardening, refine the grain and as well provide slight increases to wear resistance and corrosion resistance. The performance seen in production knives was significantly varied which is common with the more inexpensive blades.

Tool steels

Steels discussed :

Steel Carbon Manganese Chromium Nickel Vanadium Molybdenum Tungsten Cobalt Nitrogen HRC
L6 0.65-0.75 0.25-0.80 0.6-1.2 1.25-2.0 0.2-0.3 0.5 45-62
O1 0.85-1.0 1.0-1.4 0.4-0.6 0.30 0.30 0.5 55-64
A-2 0.95-1.05 1.0 4.75-5.50 0.30 0.15-0.50 0.9-1.4 58-60
D-2 1.4-1.6 0.60 11.0-13.0 0.30 1.10 0.70-1.20 58-62
M-2 0.95-1.05 0.15-0.4 3.75-4.5 0.30 2.25-2.75 4.75-6.50 5.00-6.75 62-66
M-4 1.3 0.3 4.0 4.0 4.5 5.5 58-68
Calmax 0.6 0.8 4.5 0.2 0.5 58-60
INFI 0.5 8.5 0.74 0.36 1.3 0.95 0.11 58-60
CPM  3V 0.80 7.5 2.75 1.30 58-62
CPM 10V 2.45 0.5 5.25 9.75 1.30 58-64
CPM 15V 3.4 0.5 5.25 14.5 1.3 58-65

L6 : main

Nominal composition of L6 :

Note L6 refers to a family of steels, not a specific steel :

The high-carbon low-alloy tool steels, represented by AISI L6, are designed to provide oil-hardening capabilities and higher toughness and resistance to tempering than available from plain carbon steel steels. Carbon levels are above 0.65 percent to achieve the required hardness and wear resistance. hardeningabiliy is obtained by sing at leat 1.5 percent nickel and 0.75 percent chromium, sometimes supplemented by molybdenum and vanadium.

15N20 is a very similar high nickel steel, often used in bawnsaw blades. Nominal composition of 15N20 :

Nickel has many uses in steel :

It does this by a number of ways as it has a number of strong influences on the phases present in steel and their nature. For one, as noted in the diagram on the right it is a very strong austenite stabilizer. As the carbide forming elements (chromium, molybdenum, etc.) are ferrite stabilizers, Nickel is often added to ensure ferrite isn't present in the steel.

The effect of the ductile to brittle transition temperature is so strong that nickel is often used for steels which retain toughness even in extreme cold as in cryogenic temperatures. This however requires significantly more Nickel than is in L6.

It also effects carbide formation, specifically suppressing it :

An increase of nickel content in the investigated structural steels causes a decrease of epsilon carbide concentration in their microstructure after tempering.

and also reduces the Martensite start temperature :

The investigations show that the Ms, As and Af temperatures decrease with increasing nickel and manganese contents.

which promotes a finer martensite structure.

Note the graph on the right which shows the extreme increase in toughness between L6 and a carbon steel of the same carbon content in terms of charpy impact toughness. L6 is tougher at a higher hardness than the plain carbon steels. This is why in general alloy steels are used in severely demanding applications.

In regards to hardenability, as noted in the isothermals in the right, L6 has a strongly suppressed diffusion based reaction compared to not only W1 but also O1. This is due to the fact that it has three alloying elements which retard these reactions :

Note the effect of Molybdenum is so strong on the pearlite that it splits the curve completely and pulls the pearlite away from the bainite formation as it suppresses bainite to a greater extent than it retards pearlite. In any case, for the knife maker this means L6 can use a less severe oil (slower) than O1 and thus has again lower risk of quench cracking and warping.

In regards to retained austenite, while nickel is a austenite stabilizer as is carbon, there are only a minimal amount of high carbide formers and other elements which suppress the martensite formation temperatures and thus the amount of retained austenite in L6 steels is very close to the same amount in pure carbon steels of the same carbon amount.

Note the sudden drop in retained austenite in the L series tool steels which decreases to almost zero at a tempering temperature of 300C. This is because in the temperature range of 200 to 300C there is a decomposition of retained austenite in all steels which don't have this reaction suppressed. Silicon for example will suppress it and L6 doesn't have a signficant amount of Silicon.

This temperature range is a fairly interesting one in regards to the effect on toughness in general because the reaction of L6 to tempering in this range is different depending on how the toughness is measured.

The interesting thing is that this minimum toughness peak show in the torsional data is well understood as tempered martensite embrittlement :

The embrittlement is concurrent with the replacement of epsilon carbide by interlath cementite during tempering, and the mechanical instability of interlath films of austenite (as a consequence of this carbide precipitation) during subsequent loading.

It also shows up in charpy-v notch tests and measurements of strain fracture toughness (see the above paper) but doesn't show up in unnotched charpy/izod. This may be due to its sensitivity on grain orientation, transverse tests would clarify that concern.

Knives personally used in L6 type steels :

Ray Kirk's test blades were made from 1084, L6, 52100 and D2 at various hardness levels, which were used unmarked so the steel types were unknown until after the work was completed. At high sharpening angles (20 degrees) there was no difference in initial sharpness. In edge retention on the used mats the D2 blade consistently outlasted the 52100 knife on the mat cutting which out cut the 1084 blade which outclassed the much softer L6 blade showing the heavy influence of hardness. On the bone cutting the L6 blade fared the worst again due to the low hardness. On the concrete cutting the 52100 blade had the best balance of strength and durability to minimize damage, the L6 blade again suffered due to lack of compression resistance. While there was a large difference in machinability, the blades which sharpened the fastest tended to be just the ones which suffered the least damage or wear in use, so either D2 or 52100 depending on what was cut. Note in this comparison there was an issue with the L6 blade, there was a problem with the hardening. It was included just as a check on the consistency of the testing.

The Running Dog Traditional Tanto is made from 15n20, a swedish bandsaw steel similar to L6. It was compared to a D2 custom from Mel Sorg (62 HRC, full cryo) which showed superior edge retention on hard woods . The corrosion resistance was quite low, it would rust in minutes when exposed to food acids .The Tanto was also compared to a Sub Sniper in ATS-34 cutting wood and had significantly lower edge retention, but the much greater machinability allowed similar sharpening times.

Summary : L6 is a very tough, mid-carbon steel which offers a very high toughness at a high hardness. The above blades could not readily examine these attributes as the L6 test blade by Kirk was severely hampered by lack of hardness and the Running Dog Tanto was not examined significantly as it was just on loan.

O1 : main

The following specifications cover O1 Tool Steels :

Nominal composition of O1 :

As a high carbon, low alloy tool steel, it has a very find distribution of very fine carbides, mainly cementite.

As a bit of detail on the composition, as noted in the image on the right, it only requires a maximum of 0.6% carbon to produce maximum hardness, above that there is very little increase and there are issues with retained austenite and formation of plate (vs lathe) martensite. Why then does O1 have such a high level of carbon?

The extra carbon will form carbides which are much harder than the steel (martensite) such as cementite, and more importantly since O1 has a small but significant amount of alloy carbide formers in Tungsten, Vanadium and Chromium, all of which will tie up carbon in the formation of carbides. The carbon needs to be increased above 0.6% to ensure that a free amount of carbon is left to go in solution in the martensite to enhance the hardness.

In regards to the carbide formers, the tungsten and vanadium are mainly there as they will not dissolve in the austenite and thus they pin the austenite grains as they form and thus keep the grain very small which increases the strength and toughness of the steel. These very small and very hard carbides are much harder than the martensite and the cementite 1 and thus will contribute to the low stress abrasive wear resistance over a pure carbon steel such as 1095. However to really make this significant then a lot more Tungsten is needed, several percent such as steel in the cold work grades such as F2. 2

The other significant alloy influence in O1 is the manganese which is very beneficial to steels in many respects (it is a deoxidizer) and chromium, and to a lesser extent the silicon. These elements all increase the hardenability, or ease of forming martensite. This is why O1 can oil harden but 1095 for example needs a much faster quench and is usually water hardened. For the knife user, this makes little effect, but for the knife maker, not having to deal with the extreme quench of water and the risk of cracking can be of benefit.

The chromium in the steel increases the hardenability by reducing the high temperature diffusion reactions. This means as the blade cools, the chromium stops pearlite from forming The manganese addition has a similar effect, it also reduces the formation of pearlite, but it does so in another way. manganese expanding the austenite phase to being stable (existing) lower temperatures. This ideally prevents the ferrite from forming until ideally the temperature has been reduced by the quench to the point martensite starts to form. These alloy additions to O1 over the plain carbon steels and the effect they have on the reduction of the pearlite and thus the increase in the hardenability can be readily seen in the TTT curves to the right.

O1, like most of the high carbon or high alloy steels can benefit from an extended quench where the steel is taken to below room temperature. The main reasons for this are the :

The combination of these two effects can produce an increased hardness of 2-3 HRC points and an increase in low stress wear resistance by a factor of 2. 2a .

What does all of this mean as to how the steel performs? As always, it is of benefit to look at some comments/feedback on steels from the woodworking industry as it is a very common chisel and plane steel. In general O1 is considered an entry level steel for such materials when compared to White, Blue and HSS chisels using M2 or similar steels. All of these materials will have a significantly higher carbide content, but still retain a very fine, well distributed carbide network as noted in the image on the right. 3 The apex stability in M2 and similar steels is therefore still high enough they tend to blunt by slow wear and can maintain a high sharpness.

The PM-V11 and the White Steel really do deliver. The gap between them and the A2 and O1/HCS is very large.

Now a frequent point of contention in such materials is O1 vs A2 and in general the argument is A2 will make a stronger and more wear resistant edge but it is harder to grind :

A2 is a great steel that offers a real improvement in edge retention. O1, on the other hand, is still preferred by many for its relative ease of sharpening and its ability to get sharper.

However the difference in these materials in terms of abrasive wear resistance is actually quite small and they both have the same working hardness ranges and maximum obtainable hardness. In practice then what is often seen in terms of one out performing the other is dependent more on which manufacture made which chisel in a particular steel and the random stresses on it in a particular use. Brent Beach for example compared a large range of planes in various steels and while the HSS blades in M2 did consistently offer superior performance the performance of A1 vs O2 was just a random spread around each other :

  • Lee Valley A2 , 6
  • Lie Nielsen A2 , 6
  • Lee Valley block plane A2 , 12
  • Lie Nielsen #62 O1 , 18
  • Hock O1 , 9
  • Knight O1 , 6

  • While the data show a weak increase in performance of A2 over O1, the numbers listed (which are the wear bevel sizes) differ in the random spread much larger than the difference between them so there is no statistical significance. Beach was also doing a very controlled comparison, in normal work it is even more unlikely a consistent performance increase would be seen unless careful observations were made over a very long time period.

    Maker commentary:

    Knives personally used in O1 :

    In regards to the Uddo in O1, it was used for extended slicing comparisons on 1/2" hemp and cardboard and performed well, similar to other steels in its class in regards to generally blunting by slow wear and resisting chipping and significant deformation. In order to have the performance significantly exceeded in regards to edge retention it was necessary to step up to steels such as Elmax and M4, or use a steel similar to this one, but hardened differently such as customs in 1095 which are at maximum hardness, 66/67 HRC. Of course while the edge retention slicing abrasive materials is higher in those examples, they trade off grindability and toughness to obtain the higher strength and wear resistance.

    On harder work, cutting carpet. an example of the kind of tradeoff in terms of toughness and how it influences performance can be seen. used carpet. The O1 blade from Uddo shows its versatility here compared to various steels as it could easily do extended slicing without any significant damage and just blunted by slow wear. The fact that it takes no visible damage in such work has a significant effect on the ease, or speed of resharpening. The top performance in edge retention in that comparison was seen in S30V. However the O1 blade was significantly easier to grind and when the two are combined to represent a kind of edge retention - efficiency measurement then the O1 is ahead of the S30V. Now of course if the knife is power sharpened or very coarse / high end stones are used to grind it, then this kind of measurement is moot as grinding speed can be rapidly reduced in such methods.

    The same kind of benefit was seen to an even greater extent when the knife was used to cut up some sods alongside a few other folders. It was among the fastest to sharpen as it again took very little damage and the steel has a high grindability.

    In regards to sharpening, O1 in general gets high praise for ease of sharpening, not only as noted by the woodworkers as noted previously but by knife users as well. It is one of the easier to sharpen steels possible as it has :

    As this blade is hardened for high durability, then it compromises a little on the edge retention in light use for performance in light use as noted in the above. However This means that in general the chip resistance is fairly high (compared to steels such as D2, TS-34, 10V) and in heavier use it can excel where such steels would chip. In general due to the combination of toughness and strength the edge tends to blunt by slow wear as noted in the image on the right which also increased the ease of sharpening by reducing the necessary grinding as seen in the carpet cutting previously.

    The TUSK from McClung, handled low stress cutting well and the hard edge stayed crisp a long time cutting wood, ropes and other soft media. However it chipped badly cutting light sheet metal and suffered gross damage readily on edge torques, a replacement fractured in the same manner, the maker claimed abuse. The behavior may be explained by the above torsional graph which shows strong embrittlement regions for O1 in both torsional impact and strength with a low ductility.

    A pATAK in O1 from McClung also suffered gross damage during a review. A Howling Rat was personally used to do the same work with no damage. Mike Turber also compared a ATAK in O1 from McClung to several other knives and it also suffered edge chipping cutting woods. This, as is common with critisms of McClung's knives caused significant controversy as McClung claimed the knife was a fake inspite of the knife being bought from an offical dealer of McClung's knives and other customers reporting the same behavior on multiple knives from McClung. Will Kwan also noticed problems with prying in woods as well as light chopping into metals scan down through this cashed link of a deleted thread to see Kwan's commentary.

    The Randall #1 in O1 didn't have problems with chipping however due to the low hardness (55/56 HRC) the edge retention was in general lower than slightly harder Randall #5 in 440B stainless. The 440B Randall also has of course a much greater corrosion resistance, the O1 blade will patina visibly while cutting acidic foods. When compared to harder and more wear resistant alloys such as S30V, a production folder out cut the O1 Randall by about 3:1 on cardboard. The O1 Randall machined very easily as it was soft enough to file, the low hardness does mean it could be problematic to get a crisp edge on v-rod rigs.

    As with all steels, heat treating is critical. The custom O1 blade at 63.5 HRC was compared to a Sebenza in S30V on cardboard with both sharpened to very low edge profiles, the performance was reversed from seen on the Randall and the O1 blade had much better edge retention. It also did very well slicing used carpet. It formed a patina very fast when exposed to food acids.

    Summary : O1 is a general purpose tool steel known for moderate wear resistance and toughness and low corrosion resistance. It makes a very nice light utility knife. Its performance in larger knives was not as impressive but may be due more to choices in heat treating rather than intrinsic properties of the steel.

    A2 : main

    A2 is an air hardening cold work die steel. The significant amounts of chromium and molybdenum makes it more dimensionally stable than O1. They also require much higher austenization temperatures to dissolve than the water/oil hardening steels and thus A2 is typically austenized at 1750/1800 F. The heating is usually done in stages to minimize thermal gradients in the steel and reduce the hold time at the austenization temperature to prevent grain growth.

    The dissolved alloy elements and high carbon content will cause significant percentage of retained austensite if the quench is halted at room temperature and result in a loss of 2.5-3 HRC points. With oil + cold A2 can can harden up to 64/65 HRC and will resist significant softening up to 1000 F (57/59 HRC). A2 has moderate wear resistance (A2 is 6, O1 is a 4 and D2 is an 8 : ref) and good impact toughness. The grain fracture size with standard industy heat treatment is 8.5. Some specification and performance data sheets on A2 from various manufacturers :

    Materials data :

    Maker commentary :

    Knives personally used in A2 :

    The Mission MPK took edge damage chopping while the Recon Scout from Cold Steel in Carbon V did not, which may simply be an issue of hardness. The MPK also had much lower edge retention on hemp with a DMT 600 finish compared to a Becker CU/7 which is also made from the same steel as the Recon Scout. The Mission was problematic in regards to durability and cracked in half under a light impact from a framing hammer in an attempt to cut a piece of tension bar (mild steel), no progress was made on the bar cut. Much higher durability has been seen with other blades such as the TAC-11 and Howling Rat).

    The Project I, similar to the MPK also showed damage readily just on wood chopping.

    Summary : A2 is an air hardening tool steel known for a solid combination of wear resistance and toughness. The personally used knives were not impressive in regard to durability or edge retention however this is more likely an issue with choice of heat treatment. One of the reasons could be large amounts of retained austenite which will transform to untempered martensite over time, expecially with heavy work which leaves the steel very brittle.

    D2 : main

    D2 is a cold work die steel with a much higher alloy content than A2, specifically the chromium and carbon percentages are both increased to generate a large volume of chromium carbide. D2 is typically austenized at just slightly higher temperatures, 1850 F, which like A2 is usually done in stages. It has very high wear resistance due to the carbide content which also lowers machinablity and grindability. The corrosion resistance is high for a tool steel, significantly more than A2 and it resists forming a patina strongly. D2 however doesn't have the corrosion resistance of martensitic stainless steels as most of the chromium in D2 is in the form of primary carbides due to the high carbon content and low austenizing temperatures.

    D2 has a coarse carbide structures, the primary chromium carbides which can be up to 50 microns in length, the fracture grain size is 7.5. It is commonly used in industry for punches, dies and various types of knives. It has significant retained austenite retained after quenching to room temperature which can be reduced by cold treatments. It has a very wide temper range from 300F for maximum hardness (64 HRC) and wear resistance, up to 950F (58/60 HRC) for toughness. The high temperature tempers will transform retained austenite to martensite in the cooling to room temperature after the tempering, as the ausentite is conditioned by carbide precipitation during the temper which raised the Ms point. Generally multiple tempers should be used to temper the freshly transformed martensite.

    D2 can also be soaked much hotter, up to 2050 F, which forces much more of the alloy content into the austenite which lowers the Ms point and produces a lower as quenched hardness. However there is now a much greater secondary hardening responce which can increase the hardness well above the as quenched hardness due to secondary carbide precipitation and the transformation of the retained austenite to martensite. Some specification and performance data sheets on D2 from various manufacturers :

    Other reference information :

    Knives personally used in D2 :

    The Deerhunter in D2 was compared to identical blades in AUS-8 and VG-10 stainless steel. In edge retention on hemp rope the D2 blade could cut double the amount of the VG-10 blade before achieving a similar state of significant blunting, and the VG-10 knife 50% more than the AUS-8A. However when the influence of corrosion was added by soaking the blades in lemon juice, the D2 blade was far behind the two stainless steels which were similar in edge retention on the hemp. The blade were also used for hard work, batoning, cutting bone and metal and impacted into concrete. The VG-10 blade consistently showed the lowest durability and the D2 the highest.

    Ray Kirk's test blades were made from 1084, L6, 52100 and D2 at various hardness levels, which were used unmarked so the steel types were unknown until after the work was completed, to examine sharpness, edge retention on used mats, ease of sharpening and durability by cutting concrete. At high sharpening angles (20 degrees) there was no difference in initial sharpness. In edge retention the D2 blade consistently outlasted the 52100 knife on the mat cutting which out cut the other two steels. On the concrete cutting the 52100 blade had the best balance of strength and durability to minimize damage.

    The Dozier Agent was compared to the Safari Skinner on cardboard to check it compared to another D2 blade and no significant difference was observed in edge retention in both push/pull sharpness : ref. The K2 from Dozier was compared to a small Sebenza in S30V from Chris Reeve knives on slicing cardboard and there was no significant difference in slicing edge retention between the two : ref. The K2 was also used to slice used carpet and compared to numerous other knives where it did well in general, though was outperformed by several very hard tool steels : ref. The Agent was also compared to a S30V Paramiltary from Spyderco cutting used carpet, and the edge retention was similar when the material was dry, however with cutting performed in the rain the D2 blade fell behind showing the influence of the lower corrosion resistance of D2 vs S30V : ref 1, 2. In regards to heavy impact, the Dozier Agent was subject to a variety of impacts off of hard objects and was readily outperformed by tougher steels like SR101 : ref.

    Two Spyderco Folders in S30V were compared to the Heafner bowie in D2 for edge retention on used carpet and the same behavior was noted in regards to rusting effecting edge retention : ref. In that case the D2 blade was further behind as the rain was heavier. The Heafner bowie also showed one of the drawbacks for D2 in large blades as when it accidently hit a rock when clearing some grasses the edge chipped readily : ref. However Swamp Rat knives have demonstrated highly levels of impact toughness with their D2 : ref.

    The custom from Mel Sog was used to cut a lot of hemp with various edge finishes and profiles showing the influence of both and how D2 makes an excellent rope slices with a thin edge and x-coarse finish : ref.

    The Uluchet was used for a lot of wood cutting and in general performed well, it has a fairly robust edge profile which allows it to resist damage from woods and even bone. It was also able to be used as a baton impact tool with no problems.

    There was little done with the Cuda MAXX as it was bought mainly to check the ability of the knife to take "flicking", intertial wrist openings.

    Summary : D2 is a tool steel known for high wear resistance through its very heavy chromium carbide content and high obtainable hardness. In general it makes a nice steel for fine cutting blades, at moderate sharpening angles, and especially for coarse finishes. The corrosion resistance is high for a tool steel, though it tends to pit readily in salt water soaks, and the resistance to impact is also low. There is quite a bit of variation in regards to durability, Swamp Rat D2 and Dozier's D2 were seen to be extremely different.

    Calmax : main

    Nominal composition of Calmax :

    A very versatile steel with adequate wear resistance and very high toughness. It is very suitable for low to medium production volume tooling for blanking thick production materials or in general when the tooling is exposed to high stresses.

    Note Calmax falls in the elemental range of the Uddeholm patent EP0388415B1 which was for a family of high toughness steels for heavy duty stamping.

    In regards to composition, with a small amount of Molybdenum, Calmax would be expected to have a secondary hardening response but not a strong one. The moderate amount of austenite stabilizers (nickel, manganese, or cobalt/copper) and low amount of carbon in solution (due to the carbide formers chromium, vanadium and molybdenum) would produce small amounts of retained austenite. These are indeed the properties as shown in the graphs on the right.

    With the moderate amount of Mangense and large amount of Chromium, this is a deep hardening, air hardening steel though oil would be a preferred quench for knives (to minimize diffusion reactions and precipitations of carbide from the austenite). It would resist a patina much more so than carbon steels due to the chromium in solution, but would not be stainless as it would not have enough chromium to passivate and would pit if left exposed to corrosive environments.

    The mid amount of carbon would ensure lathe matensite and promote very high toughness which would only be exceeded by the very high shock steels with even less carbon and more nickel and possibly silicon to remove TME and allow tempering in the 500F range.

    The main attraction of Calmax as a tool steel is the growing understanding that workhorse steels like D2, which have been long used in the tooling industry due to high :

    can suffer premature failure due to chipping and generate fracture. This loss can come from direct impact failure or long term fatigue.

    Calmax is far tougher than D2 and has a similar level of compressive strength and thus can equally resist deformation. In cases then when D2 tools are failing by fracture then Calmax is a solid choice over steels both due to the high impact toughness and standing fatigue.

    For knives this means that it is an option when heavy impacts are frequent part of the use and the edge may come in contact with very hard objects and the knife has to be able to strongly resist fracture. The air hardening ability also makes it attractive for makers / manufacturers who can not handle the oil hardening requirement of other tough steels such as L6.

    The main attraction however for larger knives isn't simply the toughness but the fact that it combines that toughness with a very high grindability. This means that not only does it strongly resist fracture, it is also very easy to restore to sharpness after any deformation / damage. For example compared to 3V :


    3V has a significantly higher carbide volume through the greater amount of mainly Vanadium, this also reduces the free carbon so 3V has a significantly lower hardening response than Calmax. 3V also has a very high toughness and strongly resists fracture, but the large amount of vanadium carbide means it is more difficult to grind and takes more time or more expensive abrasives to restore. Now to be clear, there is always a balance, if Calmax is wearing too fast then 3V might be a superior choice.

    However there is more to steel than impact toughness, there are other issues such as :

    As Calmax is a mid carbon, low carbide steel, while it ranks high in toughness and grindability, it will have lower fatigue strength than similar steels such as Caldie which are ESR grades and thus are cleaner. It also will have lower strength than high carbon and high carbide steels.

    Note to the right that Calmax for example has a much lower bend strength and compression strength than not only D2 but even a simple 1% carbon steel.

    Knives used in Calmax :

    The Voyager is a large blade, used mainly for chopping wood and scrub brush. Calmax worked very well in that knife, it was hard enough to resist deformation well, would tend to fail by plastic deformation when over loaded and hitting harder objects such as metals and/or rocks/dirt in the bark of trees. The high grindability due to the low carbide volume also made it very simple to grind/sharpen, even on natural stones.

    Summary : Calmax is a tool steel designed to air harden, have high toughness and solid fatigue. It works well in larger knives due to the combination of high hardness to resist deformation, toughness and fatigue strength to resist chipping/fracture and high grindability for ease of maintenance and sharpening.

    INFI : main

    INFI is a propriety steel used by Busse Combat through hardened to 58/60 HRC.

    The performance of INFI in the blades of Busse Combat has been demonstrated live by jerry Busse at live and public demonstrations at knife shows, as well as in videos and pictures, these include thousands of push cuts on full once inch hemp rope without sharpening, cuts though a hanging bundle of 10 strands of inch hemp, multiple 2x4's chopped with the knife still shaving, and very heavy prying loads and bends to a very high degrees without breaking on a fully hardened blade.

    Knives personally used in INFI :

    The straight handled Battle Mistress easily outlasting a TOPS knife in edge retention on both carpet and wood.

    The battle Mistress E was used for very heavy work to check durability and the performance was very high, resisting hammer impacts, cuts into nails, concrete and even rock with minimal damage.

    The badger Attack 3 was used mainly as a heavy utility knife and with a custom modified edge profile worked extremely well as a heavy wood craft blade.

    Summary : INFI is a tool steel known for overall solid performance with a excellent balance of corrosion resistance, toughness and edge retention. It makes a superb large blade as well as smaller blades which need to handle tougher work.

    M2 : main

    M2 is a high speed steel (HSS) which means it retains its hardness at the high temperatures induced from cutting at high speeds. High speed steels achieve this "hot hardness" through the use of alloy elements such as W, Mo and V to form secondary carbides during tempering. They require very high austeniting temperatures (2250F-2350F) to dissolve the alloy carbides. M2 is air hardening up to 66/67 HRC with oil quench and cold treatements and has very high wear resistance and low impact toughness, this is the hardness in hacksaw blades. The fracture grain size for HSS is 9 to 9.5. Some specification and performance data sheets on M2 from various manufacturers :

    other materials data :

    Maker perspective :

    Note that the tempering temperature of HSS strongly effects the corrosion resistance because chromium rich carbides both form at certain temperatures and dissolve at others :

    [...] 575 C < t < 700 C, redissolution of M4C3 and part of M23C6 carbides

    Knives personally used in M2 :

    The mini-AFCK was compared mainly to a AUS-8A stainless steel blade from spyderco and found to have better edge retention in cutting cardboard, plastics, and insulation. It also sharpened easily to a very fine edge.

    Summary : M2 is a HSS tool steel which high obtainable hardness and wear resistance with low impact toughness. It has a very fine grain structure and makes an excellent low impact cutting knife. The corrosion resistance is lower than stainless cutlery steels but high in general for a tool steel.

    M4 : main

    M4 is a high carbon, high speed steel. In the knife industry there was, and still is to a reduced extent, some promotion of it as having high toughness, however such claims are often problematic due to the lack of reference points. The materials data, even in the most positive case as presented by the manufacturer show it to have lower toughness compared to tool steels such as A2 and is similar to high carbide stainless steels such as S30V. This is not surprising as it is a high carbon, and thus high wear modification of M2.

    As noted in the image to the right, it has a high carbide volume, with well distributed small carbides (on the order of 2-3 micron). Given an optimized hardening (for strength and wear resistance) it would be expected to hold a fine sharpness for an extended period of time, have little issues with carbide tear out and aside from gross impact concerns (chopping), the main issues would likely be with difficulty of grinding.

    In a little detail on toughness as that was, and to some extent still it, one of the main promotional points of the steel, it was often promoted as being tough because of use as in the BladeSports competition blades. However it has to be realized that :

    The latter point was a well kept secret for a number of years. The M4 blades when first used would actually suffer extreme brittle failure. To prevent this the blades were under hardened by lowering the soak temperature. However even with such underhardening the blades still have a very short lifetime :

    Blade sports competitors push the limits and some of these very thin blades work harden and fracture or crack after a year or two on competition, and are replaced. Personally I used 52100 clad with 15N 20 for several years, and the knife is still undamaged.

    In regards to the effect of tempering and soak temperature on toughness :

    Blade performance was examined by hardness, 3-Point bend, impact, and CATRA (edge retention) testing. The results show that the austenitizing temperature is a significant factor that affects all mechanical properties tested. The max load in 3-Point bend test increases with the carbides fraction that can be maximized by controlling austenitizing temperature. Both austenitizing temperature and tempering temperature have significant effects on the hardness. As for the impact performance, the impact toughness increases with the carbides density. Additionally, we can achieve comparatively high impact toughness in low austenitizing temperature without decreasing hardness through lowering the tempering teperature, because tempering temperature has no significant effect on impact toughness. The edge retention of CPM-M4 steel relates to its hardness. Harder materials can provide a better edge retention for knife blade.

    As M4 is a very well used steel in industry there is a wealth of data on it including on such topics as the use of salt for heat treating.

    One of the benefits of conductive heating in salts is the use of low austenization temperatures. High speed tools heat treated in salts also require much shorter holding times at temperature.

    The difference in austenite grain can increase the traditional fine grain of such HSS (ASTM 9-10) to the ultra fine grain size of 11-12 which increases the strength and toughness at the same hardness .

    Beyond material data, an interesting point in regards to M4 as a cutting steel can be seen in the wood working industry where the standard knife demos on hemp/cardboard are replaced by wood working :

    This was a test of 5 steels used in chopping dovetails in hardwood. There were relatively good performances from 3V and M4, and superlative performances from Koyamaichi laminated white steel.

    The M4 did much better than the 10V which likely had issues with edge stability, and as well over a standard O1 chisel which would suffer from a lower hardness. Note that wear resistance was of little benefit in such a comparison as the chisel edges all blunted from wear and deformation. However chopping isn't the only use for chisels and the performance in paring was not identical :

    Taken overall, 10V struggled to hold an edge over the duration of the test. I strongly suspect that this was due difficulties in creating a good edge at the outset. This highlights the major drawback in using this steel, and it is doubtful that the average woodworker would see any advantage here. I cannot recommend 10V as a steel for woodworking blades.

    In the initial stages the laminated WS appeared to take the sharpest edge, better than any other blade in the test, but it did not hold this as well as the M4 and 3V blades. The latter made up for this by holding a good edge longest.

    This then showed the critical idea that in regards to edge retention, the stopping point is critical as the steels which had early best performance were not the same as those which had the best performance later on. However as with all such comparisons, conclusions should be left tentative without multiple runs to ensure the results are consistent.

    As for corrosion resistance, M4 has a small amount of chromium which is dissolved in the steel in the soak to prevent diffusional phases in the quench and enhance the secondary hardening response. The same chromium however also makes it significantly more corrosion resistant over simple steels such as 1095 and L6. How corrosion resistant is it? It is strong enough that it is generally considered difficult to force a patina on it compare to those basic steels. It is however not a stainless steel and there are frequent comments that the knives can in fact come with corrosion on them when bought as noted in the video on the right.

    As an interesting point of view :

    I forced a medium patina on the knife when it was new with boiling vinegar to help prevent rust and pitting. Opinions vary on the value of a patina. I cannot definitively say that it helps prevent rust but it's just something I do that seems to work for me.

    I have used the knife every day for the last 6 weeks as a fish cleaning tool. Typically I will come in and spend 15-45 minutes at the cleaning table depending on the number of fish I have. During this time, the knife blade is covered with blood, fish goo and residual saltwater from the kayak and fish. The only effect I have seen on the steel is a gradual and even darkening of the patina. There has been zero rust, pitting or red/orange residue. It should be noted that I always rinse the knife within a half hour of finishing. I usually dry it too but sometimes I just leave it out wet and have seen no ill effects from this. For the first few weeks I would spray it with a shot of wd40 after cleaning it but recently I have stopped bothering because it doesn't seem to be necessary.

    As far as ocean use its a little less capable. I took it on the kayak a couple of times. I have a small mesh enclosed cavity in the center where I kept the knife in its sheath. The cavity constantly has about a half inch of saltwater in it so the knife was basically bathing in ocean water for the entire 5 hours. When I got in there was light orange swirls on both side of the blade. No pitting at all but the rust process had definitely begun. I was able to remove all signs of corrosion in 30 seconds of light rubbing with one of those green and yellow kitchen pads.

    Note that the tempering temperature of HSS strongly effects the corrosion resistance because chromium rich carbides both form at certain temperatures and dissolve at others :

    [...] 575 C < t < 700 C, redissolution of M4C3 and part of M23C6 carbides

    That temperature range produces a maximum corrosion resistance peak.

    Knives used in M4 :

    The Air was used for stock cutting on cardboard and had very high performance. It was difficult to grind, and required specialized stones to sharpen effectively. However with those stones it would easily take a very high sharpness with very little burr formation.

    The 710 axis was used alongside the Air and was found to be similar in regards to grinding, sharpening and edge retention.

    Summary : M4 is hard to grind, easy to sharpen (minimal burr formation), but requires specialized hones. It has enough chromium to strongly resist a patina, but will readily corrode if exposed to salt water and/or acids. It is very abrasive resistant, does very well in cutting ropes and cardboard and in general works well at lower angles than coarse steels such as D2 and ATS-34.

    3V : main

    Nominal composition of 3V :

    A hot-worked, fully dense, wear resistant, vanadium-rich, powder metallurgy cold work tool steel article having improved impact toughness. This is achieved by controlling the amount, composition and size of the primary carbides and by insuring that substantially all the primary carbides remaining after hardening and tempering are MC-type vanadium-rich carbides. The article is produced by hot isostatic compacting of nitrogen atomized powder particles.

    This steel for Crucible marked a turning point in their development as they discovered something about carbide volume and nature which was critical to maximizing toughness at a given wear resistance :

    The notable improvement in toughness obtained with the articles of the invention is based on the findings that the impact toughness of powder metallurgy cold work tool steels at a given hardness decreases as the total amount of primary carbide increases, essentially independent of carbide type, and that by controlling composition and processing so that substantially all the primary carbides present are MC-type vanadium-rich carbides, the amount of primary carbide needed to achieve a given level of wear resistance can be minimized.

    It has also been discovered that in comparison to conventional ingot-cast tool steels with compositions similar to those of the articles of the invention, that production of the articles by hot isostatic compaction of nitrogen atomized, prealloyed powder particles produces a significant change in the composition as well as in the size and distribution of the primary carbides. The former effect is a hereto unknown benefit of powder metallurgical processing for cold work tool steels, and is highly important in the articles of the invention because it maximizes the formation of primary MC-type vandium-rich carbides and largely eliminates the formation of softer M7C3 carbides, which in addition to MC-type carbides are present in greater amounts in ingot-cast tool steels of similar composition.

    CPM-3V then is able to provide a very high level of toughness at a high wear resistance through approximately 5% MC type carbides which are vanadium rich.

    An interesting piece of work on 3V, 10V and 15V :

    Abrasive wear tests demonstrated that the ion-nitriding treatment and the addition of vanadium were very effective in enhancing hardness and abrasive wear resistance of HIP steels such as CPM-3V,10V, and 15V, as compared to the same steels that were only quenched and tempered. Besides, the formation of a thinner compound layer of gamma-Fe4N and VN resulted in optimum wear properties

    Note that a very coarse and very hard silicon carbide abrasive was ground against the steels (pin on disk, 500 mesh silicon carbide) which is why the initial performance of the 3V, 10V and 15V steels are so close together. Silicon carbide is comparable in hardness to vanadium carbide hence it can produce rapid wear even on high vanadium carbide steels.

    Knives used in 3V :

    The Ed Schott camp knife was used for a variety of work and the edge held up well, especially considering it was ground at nine degrees per side. It even held up to several dozen full hits from a framing hammer without gross fracture however it did have problems with a weakness through the tip.

    The Extreme Judgement showed poor performance in regards to edge retention and durability, taking damage readily in terms of chipping on woods even though the edge was 0.027-0.028" thick and ground at 15-16 degrees per side. In retrospect, this likely was caused by heat damage to the steel in the initial power grinding or similar likely transient damage and not indicative of the performance of the steel in general.

    Summary : On paper CPM-3V looks to combine high toughness and wear resistance, however the two knives used did not exhibit such performance.

    CPM-10V : main

    Nominal composition of CPM-10V :

    Design description :

    A hot-worked, fully dense, wear resistant, vanadium-rich, powder metallurgy cold work tool steel article having improved impact toughness. This is achieved by controlling the amount, composition and size of the primary carbides and by insuring that substantially all the primary carbides remaining after hardening and tempering are MC-type vanadium-rich carbides. The article is produced by hot isostatic compacting of nitrogen atomized powder particles.

    10V is the most popular of the extremely high vanadium steels developed by Crucible for cold work, resisting very high wear abrasive demands. This family of steels includes up to 20% vanadium steels, however aside from 10V, the others are not very popular and rarely used in knives.

    The very high vanadium carbide volume of 10V produces very high adhesive and abrasive wear resistance at the cost of a low grindability, apex stability and toughness. As a point of comparison vs A2 :

    Knives personally used in CPM-10V :

    The utility hunter in CPM-10V was used for a lot of cutting on various materials from cardboard, woods, plastics, hemp and used carpet. It consistently did well and outperformed steels such as D2 and ATS-34 for slicing edge retention. It did not form a patina, showing a corrosion resistance higher than steels like L6 and O1 which would be expected based on the much higher chromium content.

    Summary : CPM-10V is a very high wear steel and provides high wear resistance and hardness, producing high slicing edge retention when cutting to a low sharpness.

    CPM-15V : main

    CPM-15V is an extremely high carbon, high vanadium cold work tool steel which offers improved wear resistance over 10V.

    Nominal composition of CPM-15V :

    Design description :

    A hot-worked, fully dense, wear resistant, vanadium-rich, powder metallurgy cold work tool steel article having improved impact toughness. This is achieved by controlling the amount, composition and size of the primary carbides and by insuring that substantially all the primary carbides remaining after hardening and tempering are MC-type vanadium-rich carbides. The article is produced by hot isostatic compacting of nitrogen atomized powder particles.

    CPM-15V offers even more wear resistance than 10V through a much larger MC carbide volume. However this increased wear resistances comes at the cost of decreased :

    Knives personally used in CPM-15V :

    The Roger Dole folder was on loan so it was not used for extensive comparisons. It was not found to have an advantage in push cutting edge retention compared to D2 or ATS-34. However it did have better edge retention slicing carboard than an ATS-34 custom.

    Summary : CPM-15V is an extremely high wear cold work steel. The abrasive wear resistance is improved approximately 50% over 10V however the toughness and grindability are severely reduced. The difficulty of working/fabrication is so high that few makers/manufacturers will use it.

    Stainless steels

    Steels discussed :

    Steel Carbon Manganese Chromium Nickel Vanadium/W Molybdenum Cobalt Nitrogen/Nb Silicon HRC
    H1 0.15 2.00 14-16 6-8 0.5-1.5 0.1 3.0-4.5 58-68
    420 0.15-0.38 1.0 14 1.0 1.0 51-59
    425M 0.50-0.55 1.0 13-14 0.5 0.8-1.2 1 55-58
    Krupp 4116 0.50 14.5 0.6 0.15 0.6 56
    INOX 0.52 0.45 15 0.5 0.6 56
    12C27mod 0.52 0.4 14.5 57-58
    12C27 0.60 0.4 13.5 58-60
    13C26 0.68 0.65 12.8 0.4 58-60
    8C13CrMoV 0.8 0.4 13.0 0.20 0.10 0.15 0.5 60-61
    19C27 0.95 0.7 13.5 0.4 58-63
    440A 0.60-0.75 1.0 16-18 0.75 56-57
    440B 0.75-0.95 1.0 16-18 0.75 56-60
    440C 0.95-1.2 1.0 16-18 0.75 58-59
    AUS-4A 0.40-0.45 1.0 13.0-14.5 0.49 0.10-0.26 55-56
    AUS-6A 0.55-0.65 1.0 13.0-14.5 0.49 0.10-0.26 56-58
    AUS-8A 0.70-0.75 0.5 13.0-14.5 0.49 0.10-0.26 0.1-0.3 58-60
    AUS-10A 0.95-1.1 0.5 13.0-14.5 0.49 0.10-0.26 0.1-0.3 58-60
    154CM 1.05 0.5 14.0 4.0 55-62
    BG42 1.15 0.5 14.5 1.2 4.0 0.3 55-62
    N680 0.55 0.4 17.3 0.1 1.1 0.45 56-58
    N690 1.07 0.4 17.0 0.1 1.1 1.5 0.4 59-62
    VG-1 0.95-1.05 0.5 13.0-15.0 0.25 0.2-0.4 59-62
    MBS-26 0.85-1.00 0.3-0.6 13.0-15.0 0.25 0.15-0.25 .65 58-63
    CTS-BD1 0.9 0.6 15.75 0.1 0.3 0.37 58-63
    20CV 1.9 0.3 20 4 / 0.6 1 0.3 59-62
    VG-10 0.95-1.05 0.5 14.5-15.5 0.1-0.3 0.9-1.2 1.5 59-62
    SGPS 1.40 0.40 15.0 2.0 2.8 0.5 62
    S30V 1.45 14.0 4.0 2.0 58-62
    S35VN 1.40 14.0 3.0 2.0 0.50 60-62
    Elmax 1.7 18 3.0 1.0 0.8 55-62
    S90V 2.3 14.0 9.0 1.0 58-62
    S110V 2.8 14.0 9 3.5 3.5 60-62
    S125V 3.3 0.25 14.0 0.20 11.85 0.20 2.5 62-64
    ZDP189 3.0 20.0 65-68

    Note Phosphorus is normally considered an impurity in steels and limited to under 0.04% in most cutlery stainless, similar tolerances for sulfur, there are also small amounts of copper as well. The composition of ZDP-189 is also of some debate.

    H1 : main

    H1 is a stainless steel which through a high nickel content 6-8% allows age hardening as opposed to the method of soak/quench/temp commonly used for most cutlery stainless steels. The main advantage of precipitation hardening steels in general is that they can be supplied to a manufacturer in an condition of optimal machinability and then the only heat treatment required is an extended very low temperature soak. This grade has the near immunity to corrosion which has been verified by independent curious individuals. Some users have reported corrosion but it seems to be an issue with contamination. Spyderco's H1 blades have tested in hardness at 58 on the spine for both plain and SpyderEdge versions and 65 HRC on the edge of the plain edge version and 68 HRC on the edge of SpyderEdge model which has been proposed to be due to work hardening Some publically posted materials data on H1 :

    Knives personally used in H1 :

    A plain edge Pacific Salt in H1 was compared to a S30V and D2 blade slicing used carpet and by adjusting the grit finish of the H1 blade to a more optimal level (rougher) the performance was competitive, showing the importance of edge finish However at the same edge grit finish, the H1 knife had approximately 50% of the sharpness of the S30V blade after 254 slices through used carpet. Comparing the Pacific Salt to a Byrd Meadowlark on cardboad there was no significant difference in slicing edge retention The Pacific Salt was also compared to a Meadowlark in 8C13CrMoV and small Sebenza (S30V) with acute edge profiles slicing up plywood, and the H1 steel held its own to the 8C13CrMoV and both were far ahead of the Sebenza.

    The Alantic Salt, which has a SpyderEdge profile, used carpet : out cut a plain edged S30V blade slicing used carpet The Alantic Salt was also used for some very heavy cutting, slicing up a steel belted tire and readily outperformed several plain edged knives in various hard and high wear steels .

    Frank k (Bladeforums handle) also compared H1 to VG-10 on cardboard and found a large difference between the plain edged blades, multiples times more material cut with the VG-10 knife for both plain edged blades to have the same level of blunting. However the serrated edges cut for so long it was not possible to determine the superority of either

    Summary : H1 is a precipitation hardening stainless steel, extremely resistant to corrosion, fairly tough and ductile for a stainless steel and will tend to deform plastically rather than break when over stressed. The edge holding in cutting abrasive materials like cardboard and used carpet will be low compared to high wear stainless steels like VG-10 and especially S30V however it holds it own with many of the softer and less wear resistant stainless cutlery grades and has much better corrosion resistance.

    420 : main

    The following specifications cover 420 stainless steels :

    Nominal composition of 420 :

    Similar steels include 420J2 Azom :

    and 420HC : :

    Care has to be taken in general from inferring properties of these steels because the 420 label can be applied to steels with a carbon content as high as 0.38 % and some of the alloys such as Molybdenum and Nickel are not always present under the 420 label.

    In regards to the alloy composition, the main alloying elements are the carbon content and the chromium content. It is a little complicated to discuss as there is Molybdenum in some 420 steels and not in others and this effects the carbon and chromium dynamic as noted in the phase diagrams on the right.

    The addition of Molybdenum :

    This is why in general it isn't a common alloying element in razor blade steels which are attempting to have the smallest carbides (M7C3) to maximize the apex stability to allow the edge retention at a very high sharpness and low edge angle. Now Molybdenum of course has it uses, in particular in stainless steels it increases :

    The pitting resistance is much more improved with Molybdenum (and Nitrogen) than Chromium as shown in the Pitting Resistance Equivalent (PRE) number

    In regards to hardness, a critical property of steels for knives (and other uses), first considering that the 420 label applies to a large range of steels, Cincinnati Tool Steel which can include up to 0.3 to 0.4% carbon and a range of chromium, carbon in solution is going to vary significantly dependently on exactly what 420 is being considered. Secondly, how it is hardened is critical as well.

    As just a general reference, considering the diagram to the right and realizing that the alloy in 420 will increase the hardness slightly beyond the carbon content of the martensite, then the working hardness of this steel will typically be :

    Where the highest hardness comes from the steel which has the highest carbon, lowest chromium and minimal (or no) molybdenum and it hardened from a very hot soak, has a fast quench and an extended quench and has a low temper. Now in general, as 420 class steels often get used on very basic cutlery, they often have the simplest of hardening :

    This means in a lot of 420 knives the hardness will tend to be towards the lower end of the working range and this explains the common perceptions that such steels are soft and weak.

    Being more specific, have a look at the isothermal graphs on the right which show the properties of the steel when austenized at :

    Note the very different expected difference in Carbon and Chromium in solution at the two different temperatures. Taking the 420J2 referenced by Azom for example which can have as high as 0.36% Carbon and 14% Chromium, the martensite would be expected to have :

    However it is below the saturation line at 1100 C which would mean all of the Carbon and Chromium would be insolution at that point hence austenization temperatures at likely to only be as high as 1050 C. Note however the very large difference in martensite hardness which can result from the extra carbon insolution and the increase in corrosion resistance as the chromium is in solution as well.

    The raw data produced on hardening reflect the values predicted from the phase diagrams as shown in the graph to the right :

    The peak hardness of the 420A steel is reached at just above the austenitizing temperature of 1050 C.

    Consider the as quenched hardness > 60 HRC for the 420 steel which is in stark contrast to how it is typically used in cutlery where it is typically much softer/weaker. This is a reflection of not the inherent properties of the steel but simply that it is used on inexpensive knives which are not well hardened. Note the same work shows that the corrosion resistance of the 420 steel is signficantly higher than the 440C which would again be inferred fro the phase diagrams which predict a much higher level of Chromium in solution.

    In regards to material properties, 420 stainless is a very commonly used steel in industry for many applications and thus it is not difficult to find materials data which compares it for example to other valve steels Properties of High Strength Steels :

    In short :

  • the tensile strength is very similar between 1095, 420 and SS 716
  • the two martensite stainless steels are tougher than 1095
  • abrasive wear ranking from worst to best (17-7 PH, AISI 301, 1095, 420, SS 716)

    As well consider :

    The effect of austenitising and tempering practice on the microstructure and mechanical properties of two martensitic stainless steels was examined with the aim of supplying heat treatment guidelines to the consumer or fabricator that, if followed, would result in a martensitic structure with minimal retained austenite, evenly dispersed carbides and a hardness of between 610 HV and 740 HV (hardness on the Vickers scale) after quenching and tempering.

    In short, the actual material properties of this steel, what it can achieve are fairly different than how it is utilized in the knife industry. The largest problem with it for the user is that 420 is such a broad label it is very difficult to know exactly what to expect.

    Knives personally used in 420 :

    The Point Guard was very easy to grind, showed high corrosion resistance, but significantly lower edge retention than 52100, S30V, and 10V slicing cardboard. However the influence of sharpening angle and grit finish was shown to be a stronger factor than the steel. The knife also had fairly low strength and high ductility as the tip took a set fairly easily.

    Summary : 420 is label which covers a very broad range of steels which in general has high toughness, corrosion resistance and a strength and wear resistance similar to a carbon and low alloy steel of similar hardness. In general in the knife industry they are used in the most basic and inexpensive knives and often have very basic hardening and can seriously underperform vs the inherent ability of the steel.

    INOX : main

    INOX is one of a family of very similar steels which have a very similar working hardness, carbide structure and corrosion resistance :

    Nominal composition of INOX :

    425M has a little more Molybdenum and less Chromium so it would have a more coarse carbide structure and higher corrosion resistance. Krupp 4116 has a small amount of Vanadium (0.6%) which would increase wear resistance (slightly as it is a small amount), and refine the austenite grain. 12C27M has no Molybdenum so it would have the highest apex stability. X15TN has a significant amount of nitrogen and thus has significantly increased corrosion resistance.

    Nominal composition of X15TN :

    Note even though the carbon content is significantly lower than the other steels noted to be in this class, Nitrogen is also a martensite former which allows this steel to reach the as-tempered hardness of 60 HRC. The higher amount of Molybdenum also allows a strong secondary hardening to maximize wear resistance at the cost of toughness AD . Like all the other steels, it has a very fine distribution of very small carbides as seen in the micrograph on the right which compares X15TN to 440C.

    The main difference in this group of steels over the 420 group/class is that it has a slightly higher carbon content and can be austenized at a higher temperature to produce a higher hardness. With an accelerated quench and an extended quench (cold treatments) this group of steels can achieve an as-tempered hardness of 60+ HRC readily. Note the image at the right shows the hardening response of 12C27M without an extended quench. However care has to be taken as to the extent of these differences which in the cutlery industry can often be exaggerated.

    In regards to materials data, as these are all well known steels, it is possible to obtain the direct materials data to contrast them and thus note the differences between the 425M type steels and the 420 type steels, for example :

    Types 410, 420, 425 Modified, and 440A (see composition on Page 2) are hardenable, straight-chromium stainless steels which combine superior wear resistance of high carbon alloys with the excellent corrosion resistance of chromium stainless steels. Oil quenching these alloys from temperatures between 1800F to 1950F (982-1066C) produces the highest strength and/or wear resistance as well as corrosion resistance. A range of as-quenched hardnesses is achieved in these alloys by varying the carbon level from .15% maximum in Type 410 to .60- .75% in Type 440A.

    Further notes from the same document show :

    Much of the research is likely never to make it into cutlery but still is of interest, for example consider zone or differentially hardening of stainless steels by laser transformation hardening :

    1. A structure consisting of martensite, residual austenite and a small amount of unresolved carbide was formed due to laser transformation hardening of steel AISI 420.

    2. The improvement of properties in laser transformation hardening of steel AISI 420 was resulted from solid state transformation and dissolution/redispersion of carbides.

    3. Microhardness of this steel was measured as 700 Vickers after laser transformation hardening with power of 350 W.

    4. Wear resistance of this steel signifiantly improved after laser treatment.

    In regards to cutlery, 12C27M was developed by Sandivk for a very specific cutlery purpose :

    Sandvik 12C27M knife steel was developed for highest possible edge performance while still having good enough corrosion resistance for daily use in a dishwasher.

    Knives used in INOX class steels :

    These knives were compared for edge retention slicing cardboard in various comparisons. The Rucksack was found to be similar to a Henckles paring knife which would make sense as it is the same class of steel. The Rucksack and Mora's were found to be similar (again same class of steel) and short trials could not tell them apart from a Temperance in VG-10. However when used to cut used carpet, there a significant difference between the Rucksack and a custom in 52100 (which was significantly harder), more of a difference between another cutsom in CPM-10V. However on the same carpet the Rucksack was ahead of another much softer 52100 blade and a LM1.

    In general for all three of the blades the steel was strongly resistant to corrosion, never rusting even when let wet or exposed to food acids. The steel was also very tough and ductile and the edges would tend to deform when over stressed. They were also easy to grind and required only the simplest of sharpening stones. In particular the Rucksack was so soft it could readily be filed.

    The M16 in AUS-4A was compared for edge retention slicing cardboard to another M16 in AUS-8A, there was no significant difference. The M16 in AUS-4A was also compared to a Point Guard in and a Temperance in VG-10 and the slicing edge retention of the AUS-4A blade fell inbetween 420J2 and VG-10 as would be expected.

    Summary : In short, this class of steels are a small step ahead from 420 steels in terms of hardness, strength and wear resistance, while losing the same small step in toughness and corrosion resistance. However they are still very tough in general and are corrosion resistant enough so that when properly hardened can withstand being used in a dishwasher.

    12C27 : main

    12C27 is one of a family of very similar steels :

    Nominal composition of one of the most well known members of this class of steels, 13C26 / AEB-L :

    As a few details on some of those steels in a little more detail, 14C28N has a small amount of nitrogen to increase corrosion resistance :

    Sandvik 14C28N is ideal for knife applications which place very high demands on edge sharpness, edge stability and corrosion resistance such as chef's knives, pocket knives, hunting and fishing knives.

    Nitrobe 77 is a very unique powder metallurgy steel by ERAsteel which has a unique composition :

    At first glance it might seem odd to group it with AEB-L and other similar steels as it appears to have little in common, however this is mainly due to the fact that it uses Nitrogen significantly as the hardening agent to form martensite vs simply with carbon. While the composition is thus very different, it has similar properties to this class of steels aside from having much higher corrosion resistance. It is also capable of very high hardness (above 60 HRC) and it designed to have a a very small volume of very small hard phases. The resultant microstructure is very similar to the AEB-L and similar steels.

    Depending on hardening temperature, 94-97 % of the steel is so called nitrogen martensite, which is a martensite in which carbon in the main has been replaced by nitrogen.

    This nitrogen martensite is unusually hard for having stainless properties. The Vickers hardness has been measured to HV 600-700, which is reached by precipitation- /secondary hardening of very small secondary particles. Probably, these small particles have a size similar to those of high speed steel, and then their size is 5-20 nm. Moreover, solution hardening from the materials nitrogen, carbon, chromium and molybdenum, may contribute to the hardness of the nitrogen martensite.

    The nitrogen martensite also contains 3-6 % by weight of primary precipitated hard phase particles. These hard phase primary particles are much larger, 100-500 nm, than the secondary particles.

    The nitrogen martensite also contains 5-20 % residual austenite. The portion of this phase should be low, since the residual austenite is soft. It is tried to decrease the portion of residual austenite by repeated tempering and/or deep cooling at low temperature, for example in liquid nitrogen. Tests have however shown that for the material according to the invention, an adequate hardness, > 62 HRC, can be achieved already after two tempering treatments, and that addition tempering treatments only have a very marginal affect the hardness.

    N360 is another high nitrogen steel, with similar microstructure Nominal composition :

    These steels are common used as razor blade steel. They do so because the C/Cr based versions line on the critical tie line for martensitic stainless steels. This means the carbon/chromium ratio puts 0.6:12% of carbon/chromium into the austenite when austenized at 1100 C. This allows near maximum martensite hardness and high corrosion resistance.

    As it is quite close to the carbon saturation line when austenized at 1100C there is only a small only a small volume fraction of sub micron carbides left undissolved. As noted in the picture at the right the average size of the chromium carbides is less than a micron and he carbide volume is less than five percent. The type of carbides form will also be of the M7C3 type which are the samaller and harder chromium carbides.

    Roman Landes has measured the apex stability of steels which is the ability to hold a high polished edge at a low angle and found as published in his book "Messerklingen und Stahl: Technologische Betrachtung von Messerschneiden" that this class of steels has the highest apex stability. This is due to the combination of very high hardness, fine austenite grain and small volume of well distributed, very small carbides.

    Note in more detail on the size of the carbides, due to the very small volume of primary carbide in AEB-L and similar steels, the size of the carbides is even much smaller than steels which are made from powder metallurgy.

    As shown in the images at the right, the size of the carbides in both ATS-34 and RWl-34, which is a similar steel made from powder metallurgy are much larger than the carbides in AEB-L :

    Even though in general powder metallurgy does reduce carbide size, which can be seen as it reduces the carbides in ATS-34 by more than half the size, in very high carbide steels which have larger carbide types, the carbides can still be far larger than AEB-L.

    Another comparison of coarse and fine carbide size is shown at the right showing 440M vs 440C. 440M is a Chinese bearing steel, same class as AEB-L :

    the comparison steel is :

    This was a steel designed to have similar properties as 440C in regards to hardness/corrosion resistance and to just lower the carbide fraction to enhance various bearing properties :

    Recently, modified 440 type martensitic stainless steel (containing 0.63C-12.7Cr) has been developed. By reducing the content of carbons, chromium and controlling the size and amount of carbide particles, the properties of the new-developed material can still maintain as that of SUS440C type martensitic stainless steel.

    -Microstructure and Mechanical Properties of 0.63C-12.7Cr Martensitic Stainless Steel,Chih-Chung Lina, Yuli Lin

    Note again the very large carbides in 440C vs 440M.

    In regards to hardening, Landes has described his heat treating procedure for 13C26 :

    Note the use of two preheats to minimize the soak time to minimize grain growth. The use of an oil quench to maximize hardness and multiple temper and deep quench cycles to minimize retained austenite.

    Verhoeven has also studied this group of steels and discussed it in his book :

    From this discussion it appears that the two steels discussed in Chapter 13, Uddeholm AEB-L and Sandvik 12C27, along with the similar steels of Table B1, (DD400 and AUS6) provide the best combination of properties desired in a knife blade:

    (1) An as-quenched hardness in the 63 to 64 Rc range which should provide high wear resistance.

    (2) An adequate level of Cr in the austenite formed prior to quenching to provide good corrosion resistance, a bit above the minimum 12 %Cr.

    (3) The presence of fine arrays of the K1 + K2 chromium carbides to enhance wear resistance plus the absence of the larger primary chrome carbides that promote pull-out at sharpened edges.

    And also in in research paper comparing it vs several other carbon and low alloy steels :

    It has long been taught and remains a widely held view that stainless steel blades cannot hold an edge as well as a high carbon steel blade. The second study addresses this question by comparing the cutting performance of stainless blades made from AEB-L to 52100 and 1086 at a hardness of HRC = 61. The AEB-L stainless steel is recognized as one of the better stainless compositions that allows optimization of corrosion resistance at this high hardness level while minimizing the presence of large primary carbides, which are prone to pull-out along the knife edge

    In short, Verhoeven found that AEB-L had a slight advantage over the carbon and damascus steels at the same hardness (61 HRC) in CATRA tests.

    In regards to corrosion resistance, this class of steels is behind the 12C27M steels which are themselves behind the 420 class steels as noted in the above. However there are two points to be made immediately :

    The corrosion resistance is so high in the 420 class steels that it takes very little in the way of hardening to produce it. This is because the ratio of C/Cr is very low and so the chromium can freely dissolve in the austenite and there is little carbon to form carbide to precipitate in the cooling after the soak. However in AEB-L and similar steels this isn't the case and therefore steps have to be taken to ensure the full and necessary amount of alloy go into solution and that it doesn't precipitate out in the quench.

    As seen in the YT video on the right, when properly hardened these steels can withstand extended exposure to salt water and food acids which in general might make them have enough practical corrosion resistance for many.

    Knives used in this class of steel :

    The Kershaw Vapor in general had issues which are commonly found in this class of steel. This steel, while designed as a razor blade steel and which can offer high performance only does so when it gets a hardening which produces the required material properties. The Vapor was very problematic to sharpen, produced a gummy edge and in general had poor performance. This was likely due to high levels of retained austenite as indicated by Kershaw's very low choice of hardness. If that hardness was desired, as indicated elsewhere a more sensible choice would be the 420 class steels and harden them as to produce martensite.

    Summary : this class of steel is a step up in hardness, apex stability, and wear resistance from the 12C27m class steels. However it also has a corresponding reduction in corrosion resistance and toughness and ductility.

    8Cr13MoV : main

    8Cr13MoV is one of a family of very similar steels which includes :

    Typical nominal compositions :



    A quick check of the phase diagram on the right shows the following martensite composition at an 1100C austenization :

    The expected comparison of those steels would be that 8Cr13MoV could be made slightly harder (1-2 HRC) and AUS-8A would be significantly more corrosion resistant. They have a carbide volume between 440C and AEB-L which can be inferred from the relative position off of the carbon saturation line. The potential for high carbon in solution in 8Cr13MoV makes it one of the rare stainless steels used in cutlery which is commonly hardened above 60 HRC. In the Byrd line Spyderco's blades are typically 61 HRC. However the relatively low chromium in solution also means it typically has issues reported with corrosion resistance for a stainless steel.

    However care has to be taken to understand that the elemental composition of these steels actually over laps and thus the previous comparison is based on average samples of each. A quick look at the nominal description of AUS-8 shows for example that these two steels are possible and would both be called AUS-8 :

    The first one has a very low carbon to carbide ratio and thus would be softer but very corrosion resistant. The second one is the opposite. In a bit more detail, again looking at the phase diagram the alloy in solution would be expected to be :

    Note the Melt-V version of AUS-8 is near identical to the above noted solution based on the nominal composition of 8Cr13MoV. However Melt-A has a carbon/chromium ration similar to the INOX type steels.

    Knives personally used : in 8Cr13MoV

    Knives personally used in AUS-8A :

    The Deerhunter in AUS-8A was outcut by 50% by a VG-10 Deerhunter by about 50% and by about 3:1 by a D2 Deerhunter on 3/8" hemp. However when the influence of corrosion was added by soaking the blades in lemon juice, the AUS-8A blade matched the VG-10 both were far ahead of the D2 blade. For cutting bone, metal and impacted into concrete, the AUS-8A blade was consistently inbetween the VG-10 (low) and D2 (high) blade in regards to strength/durability. There was no difference seen in maximum obtainable sharpness at 22 degrees per side and while AUS-8A ground a lot easier than VG-10 and especially D2. Another Deerhunter in AUS-8A was compared to two dendritic knives cutting cardboard and found to have similar edge retention in regard to push cutting sharpness but behind in terms of slicing aggression. There was no difference noted in ease of sharpness nor initial cutting ability.

    The Calypso Jr. had lower edge retention than D2 (62 HRC), VG-10 (60/62), and CPM-10V (62.5 HRC) for in edge retention on ropes, cardboard and woods.

    The medium Voyager was serrated and the the teeth tended to snap readily with overstressed and not deform.

    The large Voyager was behind a U2 in SGPS on cardboard, wood and hemp.

    The Meadowlark had reduced edge retention compared to a Manix (S30V) slicing cardboard but ahead of a Point Guard from CRKT (420J2). It matched the performance of a small Sebenza (S30V) in push cutting edge retention on cardboard but again was behind on slicing slicing aggression. It compared well to a (H1) for for edge retention slicing cardboard. Slicing used carpet, the Meadowlark was similar to a Paramilitary in regards to edge retention. Whittling plywood, The Meadowlark had a slight advantage in edge retention on both the push and slice over a Pacific Salt and a major advantage over the small Sebenza which had durability problems.

    Slicing used carpet the Cara Cara was was comparable in performance to a UK Pen (S30V) and Dozier K2 (D2). However the serrated section was among the top showing the advantage of geometry as well as steel in edge retention. The Cara Cara was also used for some heavy prying in woods where it showed a solid combination of strength and durability for a stainless steel.

    The Finch was compared to a no-name chinese knife on slicing cardboard and showed significantly better edge retention.

    Summary : 8Cr13CrMoV offers improved wear resistance over 13C26 through a larger volume fraction of carbides. It also has slightly higher maximum hardness and slightly lower corrosion resistance. In general, experience with a large number of knives shows its edge retention in slicing abrasive materials is what would be expected based on hardness/carbide volume. It is ahead of similar steels such as 420 but behind steels such as ATS-34 and D2. However in push cutting edge retention it tends to do much better in comparison and can often match or exceed steels such as S30V where the higher carbide volume isn't an advantage.

    440 : main

    Nominal compositions of the 440A series steels :


    • Carbon : 0.6-0.75%
    • Manganese : 1%
    • Chromium : 16-18%
    • Molybdenum : 0.75%


    • Carbon : 0.75-0.95%
    • Manganese : 1%
    • Chromium : 16-18%
    • Molybdenum : 0.75%


    • Carbon : 0.95-1.2%
    • Manganese : 1%
    • Chromium : 16-18%
    • Molybdenum : 0.75%

    The 440 series of steels are high carbon, air hardening martensitic stainless steels. In contrast to steels such as 420HC, 12C27 and 14C28N, these steels are designed to have very large amounts of primary carbide to increase wear resistance. Using the phase diagram to the right it is possible to estimate those carbide fractions and the amount of carbon and chromium in solution when these steels are austenized. At 1100 C :

    Note the huge change compared if they were austenized at 1000C :

    The 1000 austenization temperature isn't high enough to put enough chromium or carbon in solution and thus those steels would suffer from lack of hardness and corrosion resistance if so under hardened.

    This is clearly shown in the materials data which look at hardness as a function of austenization temperature such as shown in the graph to the right :

    The peak hardness of the 420A steel is reached at just above the austenitizing temperature of 1050 C. The 440C steel has a higher hardness value than the 420A steel at the austenitizing temperature of 1100 C.

    -Corrosion and microstructural characterization of martensitic stainless steels submitted to industrial thermal processes for use in surgical tools

    Using the 1100 C austenization ratios, as these two elements in solution strongly influence the hardness and corrosion resistance, it is to be expected that these steels will be similar in those respects to the following, again assuming optimal hardening :

    Actual materials data :

    Material loss in mm/a when exposed to acetic acid (5% at 120 F):

    Considering the phase diagram predictions of carbon/chromium composition :

    It would thus be expected that 420 would have the highest corrosion resistance, followed by 440A (when austenized at 1000C) and that 425M would be the lowest and the differences would be similar in size. This exactly matches the corrosion resistance data.

    However, while the 440 series of steels are similar in terms of hardness/corrosion resistance to those steels listed, they are very different in microstructure, in particular they have much large carbide volumes. This carbide volume can be estimate from the distance they are from the carbon saturation line in the phase diagrams. As they are very far away compared to the AEB-L class steels they would be expected to have a much more coarse carbide structure and a higher volume. This is exactly what is shown in the two micrographs on the right which compare :


    • Carbon : 1.08%
    • Manganese : 0.4%
    • Chromium : 17.3%
    • Molybdenum : 1.1%
    • Vanadium : 0.1
    • Cobalt : 1.5%


    • Carbon : 0.95-1.2%
    • Manganese : 1%
    • Chromium : 16-18%
    • Molybdenum : 0.75%

    Note the much large carbide size in N690. In regards to the Cobalt, this is added to stainless steels for a number of reasons. In very high carbide steels it is often added as it is an austenite stabilizer and thus keeps ferrite out of the steel in the as-quenched form. It has other benefits in high speed steels such as increasing hot hardness and strength and allowing very high austenization temperatures which are necessary to give the very strong secondary hardening in high speed steels.

    Because of the higher carbide size and volume it would be expected that in general the 440 family of steels has a higher wear resistance, but lower toughness than the steels for which it was compared on the basis of equal C/Cr elements in solution but had a smaller carbide volume. This is again shown in the materials data which shows a much higher toughness for 420 and a decreasing toughness from 440A to 440C :

    Impact toughness, izod v-notch

    • 420 : 48 HRC : 14
    • 440A : 51 HRC : 5
    • 440B : 55 HRC : 4
    • 440C : 57 HRC : 3
    -The Mechanical Properties of Stainless Steel, David Rowlands,Sassda

    Note this is a common industrial hardening, it lacks an extended quench and thus the hardness is reduced from the maximum possible. The soak temperature is also likely less than optimal for knives which were trying to obtain the highest strength and wear resistance.

    In regards to toughness, there are development in steel processing to improve the toughness in these steels such as the addition of small amounts of other elements (Titanitum and RE elements) which adjust the nature of the carbides which form and thus increase the toughness significantly Patent CN 201210092708 . Titanium is an extremely strong carbide former and it will bond with carbon preferentially over chromium and thus reduce the carbide size and free up the chromium to enhance the corrosion resistance.

    In regards to carbide volume, another comparison of 440C and an AEB-L type steel is shown at the right. Again note the very large difference in carbide size, 440C has both a :

    the comparison steel is :

    This was a steel designed to have similar properties as 440C in regards to hardness/corrosion resistance and to just lower the carbide fraction to enhance various bearing properties :

    Recently, modified 440 type martensitic stainless steel (containing 0.63C-12.7Cr) has been developed. By reducing the content of carbons, chromium and controlling the size and amount of carbide particles, the properties of the new-developed material can still maintain as that of SUS440C type martensitic stainless steel.

    -Microstructure and Mechanical Properties of 0.63C-12.7Cr Martensitic Stainless Steel,Chih-Chung Lina, Yuli Lin

    In further detail on the carbide volume, while the 440 series steels do have enough chromium and molybdenum to produce a significant secondary hardening response it isn't enough to produce a strong enough response to maximize wear in the high temperature as the hardness can only just be maintained not maximized.

    Note further in the images in the right, even though there is a strong secondary carbide volume precipitation at 600C the hardness is severely reduced to such an extent it drops to the low 40's. Due to the extreme loss of hardness the wear resistance is minimized at the high tempers.

    It can be seen clearly that pins subjected to high tempering temperature caused high volume loss values and high wear rates.

    - Dry Sliding Wear Characteristics of AISI440C Martensitic Stainless Steel, Dararat Arparjirasakul, Tapany Patcharawit, and Usanee Kitkamthorn

    As 440C is a well known bearing steel, there is a wealth of data on its properties including response to hardening and issues such as extended quenches (room temperature, dry ice vs liquid nitrogen) :

    Hardening :

    • austenized at 1010C
    • oil quench
    • 200C temper

    with three different quench ending points :

    • room temperature (CHT)
    • dry ice (SHT)
    • liquid nitgoren (DHT)

    Retained austenite, hardness and impact toughness :

    • CHT : 29% RA, 57 HRC : 2.4 J
    • SHT : 8% RA, 59 HRC : 2.2 J
    • DHT : 6% RA, 61 HRC : 2.0 J
    - Influence of Deep Cryogenic Treatment on the Mechanical Properties of AISI 440C Bearing Steel A. Idayana, A.Gnanavelbabub*and K. Rajkumarc

    Use of dry ice to extend the quench has a very large difference on reduction in retained austenite and increases the hardness while having a minimal loss of toughness (< 10 %). Using liquid nitrogen has only minimal further reduction in retained austenite but further increases the hardness, likely slightly enhance through eta carbide precipitation.

    Knives used in 440 stainless :

    The Sog Seal 2000 was compared extensively to a MPK-Ti and found to be similar in edge retention, far more brittle, far less corrosion resistance, and with better resistance to impaction.

    The Randall #5 in 440B at 56/57 HRC in general compared well to the O1 Randall at 55/56 HRC in regards to tough tasks such as digging in rocky soil where both knives suffered similar wear/deformation. The 440B Randall also in general better edge retention than the O1 Randall, possibly due to the higher hardness, wear resistance and corrosion resistance. When compared to a Spyderco Manix in S30V the 440B Randall #5 was however significantly behind in edge retention slicing cardboard and scraping woods.

    David Boye's dendritic 440C is 440C used in an as cast state which means the carbides retain their large and extended branching structure. Boye promotes this on the basis of aggressive cutting action. The Boye hunter in dendritic 440C was compared to the dendritic cobalt version in the kitchen and the steel blade had much better edge retention mainly due to a higher durability which reduced edge damage. The same advantage in edge retention favoring the dendritic 440C over cobalt was seen on half inch hemp. The Boye hunters were also compared to the Deerhunter on cutting cardboard and the sharpness checked for both push and slicing sharpness. In general the performance of the Boye blades was much higher than the Deerhunter in regards to slicing aggression but they were similar in regards to push cutting.

    Summary : The 440 series of stainless steels offers a higher wear resistance than steels such as 420HC and AEB-L through a much larger carbide volume. However this also lowers the toughness and grindability. Progressing from 440A to 440B to 440C is an increased trend in gaining hardness and wear resistance with a trade off of reducing toughness, grindability and corrosion resistance.

    154CM : main

    Carbon Manganese Chromium Molybdenum HRC
    1.05 0.5 14 4.0 58-63

    154CM is modified 440C, 3 percent of the chromium removed and 3.25% molybdenum added. With a 1100C austenization there is 0.58/10.6/3.4% C/Cr/Mo dissolved. The carbon content suggests a maximum hardness of 62/63 HRC after an oil/cold quench + 150C temper which is confirmed by Crucible's data sheet. Even though there is less chromium, there is a higher volume fraction of chromium carbides vs 440C, specifically 17.5 vs 12 according to the S30V data sheet, though there is no specification of the austenization temperatures which effect this significantly. The molybdenum also forms harder harbides than chromium and increases pitting resistance and gives a strong secondary hardening responce. The lower percentage of chromium also gives a finer carbide size than 440C.

    154CM can be tempered both low or high and both give up to 62/63 HRC. The higher temperature is typically used for hot hardness and wear resistance the low one toughness and corrosion resistance. Some knifemakers such as Bob Engnath have argued that the higher temper gives better edge durability, however work by Landes shows that the higher temper reduces edge stability as discussed in Messerklingen und Stahl. ATS-34 is the same steel under a different name made by Hitachi who have published a comparison of the high/low temper. Spyderco has performed Q-FOG and Catra which show VG-10 is superior in both corrosion resistance, initial sharpness and extended slicing aggression than ATS-34. The picture of ATS-34 on the right is from Messerklingen und Stahl.

    There are also two powder metallurgy versions of 154CM; CPM-154CM made by Crucible and RWL34 which has 0.2% vanadium to refine the grain and add wear resistance. Knives personally used in 154CM/ATS-34 :

    The Buck/Strider Solution was used on some birch hardwood and the edge fractured readily during light chopping. It also chipped out readily during some light digging and cracked in half under a light hammer hit. The Buck/Strider folder did not show the same brittle failure as the Solution however the grinds were so thick a direct comparison was not possible.

    The Silver Trident and Mora 2000 in 12C27mod were compared slicing 3/16" cardboard with 10 primary and 15 secondary edges set by a 600 DMT pad. The Mora 2000 had much better extended slicing aggression which is surprising and likely indicates the Trident's steel was defective.

    The WB was used for some heavy tip work and able to dig in woods where the tip cracked readily on the TOP's Steel Eagle (1095), however the geometries are dissimilar so a steel contrast isn't possible. The WB was also chopped into a concrete block alongside and took more damage than a 52100 forged bowie from Ray Kirk with more acute edge and the WB took far less damage showing the the extreme difference in impact toughness between the two steels.

    The PAB had much better edge durability chopping wood compared to a Machax which chipped out even when the edge profile was more obtuse 26 vs 22 degrees for the PAB. This lead to drastically better edge retention when the profile on the Machax was thinned out so it would have the same level of chopping ability.

    The MNK-1 tip was flexed in wood and broke at 15-20 degrees. The Sub-Sniper had signifcantly better edge retention than a Running dog Traditional Tanto in 15n20 (57/58 HRC) carving wood but the much greater grindability of 15n20 allowed similar sharpening times.

    Summary : 154CM/ATS-34 is a high carbon stainless steel generally regarded as a direct upgrade to 440C. It has a high wear resistance for a stainless steel and a low edge stability both due to the large carbide fraction with primary carbides as large as 25 microns. It is one of the more brittle stainless steels and in general works best on smaller blades indended for extended aggressive slicing.

    VG-10 : main

    Carbon Manganese Chromium Vanadium Molybdenum Cobalt HRC
    0.95-1.05 0.5 14.5-15.5 0.1-0.3 0.9-1.2 1.5 58-62

    VG-10 is a high carbon stainless steel, similar to 154CM with less molybdenum and the addition of cobalt and a small amount of vanadium. The vanadium acts mainly as a grain refiner and the cobalt is promoted to enhance carbide stability (Takefu Speciality Steel webpage on VG-10).

    In regards to materials data, spyderco has performed q-fog testing which show VG-10 to be superior to ATS-34/55 in corrosion resistance and CATRA tests which show better initial sharpness and edge retention in CATRA testing and superior to S30V in terms of corrosion resistance but lower in edge retention in extended CATRA testing. Fallkniven has performed break tests on their laminated VG-10 blades which show a higher tensile point for the laminated blades but a lower yield point. So they take a set sooner than pure VG-10 but the laminates will bend further before they break.

    VG-10 is an interesting steel and unfortunately it is a Japanese steel and thus direct information on it isn't as accessible as many other steels which are very similar in class aside from the data from Spyderco. However there are some very similar steels for which there is a lot of information. 19C27 for example is a simple steel from Sandvik and it is easy to find not only composition but micro-graphs and detailed hardening directions and even reasoning on design/composition and scope of use:

    Sandvik 19C27 is Sandvik's most wear resistant knife steel grade and developed for abrasive applications. Sandvik 19C27 is the odd grade in the Sandvik knife steel portfolio because it's a coarse carbide grade, unlike the other Sandvik knife steel grades.

    The coarse carbide grades excel at wear resistance but do not allow keen edge angles and have limited edge stability, due to the sacrifice of toughness related to the coarse microstructure.

    Sandvik 19C27 is developed for industrial blades for cutting cardboard and tough fiber materials. The world class wear resistance is the main reason why this grade should be selected. Sandvik 19C27 is limited in corrosion resistance and we recommend surface coating on Sandvik 19C27 for knife applications to avoid corrosion issues.

    Now as a point of clarification, estimating properties of one steel from another when many elements change is very difficult, however in this case it isn't impossible because there are many changes which both make the same type of influence and there are no direct contradictory influences :

    A micro-graph of 19C27 is shown on the right compared to AEB-L. Note 19C27 has both a larger volume of carbides and much larger primary aggregates up to 15-20 microns in size. This is perfectly consistent with Sandvik's description of it being a coarse steel for cutting abrasive materials more so than retaining a fine cutting edge.

    This steel thus isn't designed as a razor blade steel (such as 13C26, AEB-L, 12C27, or the non-stainless steels such as 50100-B, W1, etc.) but is designed for maintaining an aggressive slicing edge and to more strongly resist wear. Other steels in the same class are MBS-26, AUS-8, and 8Cr13MoV.

    Now clarity has to be noted in any such statements because they are all relative, 19C27/MBS-26/VG-10 for example has a higher ability to hold a fine cutting edge vs an even higher carbide steel. As with all relative style rankings, the point of views or reference standards are critical.

    Knives personally used in VG-10 :

    The Spyderco Lum was used for many comparisons and showed a slight disadvantage over S30V at the same angle/grit finish. However these differences are so small that it takes multiple runs averaged with the same angle/grit finish and constraining the cutting to a controlled speed, style of cut and statistical sampling of the material being cut.

    If the comparison is not as controlled then those kind of small differences and even much larger ones can be difficult to impossible to spot. Note the image on the right which shows a comparison of the Lum vs three other knives in three different steels :

    While the comparison is strictly controlled in terms of edge angle, apex angle and grit finish, type and nature of cutting - the material used was not random sampled and thus due to that one factor alone it takes approximately ten repeated trials for the data to show there is any difference at all between any of the steels.

    The Fallkniven A1 took little damage from digging in rocky soil aggressively and was restored to a level of functional sharpness just on the blade of a pick and further on a rock . However much of the durability was due to the heavy edge cross section. The Fallkniven H1 suffered a cracked tip during digging in 2x4's which was surprising as the cross section is very thick. However a replacement did the same work with no issues. The S1 was used to dig in many 2x4 up to the point where the board just cracked in half with no damage and the S1 has a thinner cross section than the H1. When overstressed the Fallkniven F1, S1 and WM all shattered and broke in multiple pieces.

    The Fallkniven F1 was significantly behind in extended ege retention than a D2 custom at 62 HRC and well behind a a CPM-10V custom at 62.5 HRC cutting card stock, pine and RS-232 cable, with the sharpness tested cutting cotton, light fabric and slicing rubber. The F1 was also compared in detail to a Spyderco VG-10 blade which was slightly harder and the Spyderco knife showed slighty better edge retention on use car mats but had less durability in chopping wood, cutting copper and impacts from a mild steel rod. The F1 was also compared to a MEUK in Talonite with both having a medium finish (600 grit DMT rod) and had no significant difference in edge retention either in push or slicing aggression after an extended cardboard cutting session. On an extended salt water soak, an F1 in VG-10 was ahead of an F1 in ATS-34 and both were well ahead of the same D2 custom at 62 HRC but well behind a MEUK in Talonite. for an extenesalt water corrosion. Cutting various metals the VG-10 F1 had better edge durability than the ATS-34 version and both had much better durability than the MEUK in Talonite. The VG-10 F1 was also used for some harder metal cutting alongside an Ontario machete where it had significantly lower edge durability cutting thick metals than an Ontario machete.

    The D'Allara had some issues with durability concerns with the serrations however they are ground significantly more acute than other Spyderco knives. The Endura saw a lot of work on various media, including a lot of work outside on woods, and various chopping and splitting tasks and generally responded well. The Endura was even harshly blunted by some sod work and sod work and resharpened on a piece of concerete.

    The Bill Moran Featherweight was compared to CPM-10V (62.5 HRC), D2 (62 HRC) and AUS-8A (58/59) on cardboard, rope and pine and significantly ahead of AUS-8A in edge retention but behind D2 and CPM-10V). It was also used for work alongside the Fallkniven F1 as noted previously.

    The Temperance matching the performance of a Spyderco Military slicing used carpet and also stayed with the Military on cardboard in push cutting sharpness but fell behind significantly in slicing aggression this makes sense considering the similar hardness but much higher wear resistance of the Military in S30V. There was a large difference in grindability noted, removing the same amount of metal from S30V took significantly longer than with VG-10, about two to one. The Temperance was also compared to a Point Guard in 420J2 and M16 in AUS-4A slicing cardboard with an aggressive finish, the Temperance was was distinctly superior to both in slicing edge retention.

    The Deerhunter in VG-10 was compared to identical blades in D2 tool steel and AUS-8A stainless steel. In edge retention on hemp rope the D2 blade could cut double the amount of the VG-10 blade before achieving a similar state of significant blunting, and the VG-10 knife 50% more than the AUS-8A. When the influence of corrosion was added by soaking the blades in lemon juice, the D2 blade was far behind the two stainless steels which were similar in edge retention on the hemp. The blade were also used for hard work, batoning, cutting bone and metal and impacted into concrete. The VG-10 blade consistently showed the lowest durability and the D2 the highest.

    The Al Mar Sere was used mainly to examine the lock under batoning, the edge was uneffected by impacts which destroyed the liner, however the tang impacted readily even during chopping. The blade required a high force to take a set while prying, however it broke readily under impact from a wooden baton and showed little ability to resist direct impact.

    Summary : VG-10 is a high wear stainless steel in the same class as 154CM however has a reduced secondary hardening response.

    BG42 : main

    Carbon Manganese Chromium Vanadium Molybdenum Silicon HRC
    1.15 0.5 14.5 1.2 4.0 0.3 55-62

    BG42 is a ball bearing steel which also has very strong hot resistance. It is basically to 154CM modified with a significant increase in vanadium and a small increase in carbon and chroimum. Due to the ability of vanadium to strongly carbide and the need to produce a strong secondary hardening, BG-42 is austenized at 1121 C or 2050 F which is much higher than most cutlery stainless steels. It is also made by Vacuum Induction Melting/Vacuum Arc Remelting (VIM/VAR) which refines the steel to a very high purity and thus offers very high fatigue properties. Q-fog tests by Spyderco show BG-42 as hardened by Reeve to have superior corrosion resistance to ATS-34/55 and VG-10. The trade name by Timken for this steel is Lescalloy. Blades used in BG-42 :

    The Recondo has a very inefficient grind for a cutting tool so it was not possible to obtain much information about the ability of the steel in that regard. The knife could have been reground into a decent cutting tool but it had severe problems with ergonomics and other aspects. It did suffer brittle failure fairly easily which is in general to be expected of that class of steel.

    Summary : BG-42 is a very high purity, high wear, martensitic stainless steel which offers very high heat resistance. The hot hardness is likely not of significant benefit for knife blades but the other attributes often cause it to be highly praised among discriminating users. It is generally regarded to be in the same class as 154CM but better in most respects for cutlery due to the VIM/VAR process and use of a small amount of vanadium carbides to reduce the large chromium carbides.

    SGPS : main

    Carbon Manganese Chromium Vanadium Molybdenum Silicon HRC
    1.40 0.40 15.0 2.0 2.8 0.5 62

    SGPS is a powder metallurgy martensitic stainless steel made by Takefu Speciality Steel. Knives used in SGPS :

    The U2 was compared to a had better edge retention slicing cardboard than a large Voyager in AUS-8A, and was even more superior in edge retention slicing unsupported hemp and still better e but to a much smaller degrees push cutting pine. It was also compared extensively to a Jess Horn in ZDP-189 and had better extended slicing aggression on cardboard however the primary angles were too different too alow a comparison of the steels.

    Summary : SGPS is a powder metallurgy steel which is in the same class as S30V, as a high wear alternative to steels like 154CM.

    CPM-S30V : main

    CPM-S30V is Particle Metallurgy high carbon, high vanadium stainless steel made by the Crucible Materials Corporation and designed by Dick Barber as a cutlery steel. The prime incentive in its design according to Dick Barber, a metallurgist who worked at Crucible and developed the steel, was to allow heat treating without austenizing temperatures above 1950 F to make it more readily usable by knifemakers as compared to S60V and S90V. S30V is also much easier to grind due to the lower vanadium content compared to S60V/S90V and for the same reason has a lower wear resistance.

    Problems with S30V have been frequently reported on internet discussion forums just cutting soft materials such as cardboard, corn stalks, plastics and wood. The frequency of defects is so high that users have reported several defective blades. Sometimes the problems have been solved with sharpening but others have persisted through repeat sharpenings and use. Others have even seen problems with more gross fractures under similar light work. Commonly it is found that S30V blades tend to blunt by chipping at a microscopic level. Direct comparisons have also been done and found that S30V is a small Sebenza in S30V to be less durable than 425mod and an other judges a small Sebenza in S30V comparable AUS-6A.

    The problems reported with S30V have been argued by representative from Crucible to be due to possible problems due to overheating due to low grindability or issues with heat treatment, ironically these are two of the initially promoted strong points of the steel and a huge effort was made to hype the chipping resistance of the steel which included promoting it hugely in toughness especially hyping the importance of the transverse toughness.

    Knives personally used in S30V :

    The RSK showed the same kind of problems reported on S30V as noted in the above. It fractured readily even during sharpening.

    The Green_Beret could only match the edge retention of a Buck 119 in 420HC. similar in regards to durability both on light metals and on hard contacts, it was in the same class as the Buck 119. However, Reeve under hardens S30V and thus the performance isn't likely to be comparable to other S30V blades or the designed/intended use of the steel.

    The small Sebenza was similar in push cutting edge retention to a Spyderco Manix also in S30V, a K2 in D2 and a Meadowlark in 8C13CrMoV. It did however show lower edge durability carving plywood compared to a a Pacific Salt in H1, Calypso Jr in ZDP-189, and the Meadowlark on plywood. Similar to problems noted by others with edge durability at low angles. However edge retention slicing cardboard was improved over the same Meadowlark and two Temperances in VG-10 and was similar to a Mel Sord blade in D2. The corrosion resistance and its effect on slicing edge retention on cutting cardboard was also checked and it was found that a Rucksack in INOX had the highest corrosion resistance followed by the small Sebenza then a Calypso Jr. in ZDP-189 and the Meadowlark in 8Cr13MoV. However even though it rusted the least visibly, the Rucksack was behind the mall Sebenza in edge retention, though the spread in the trials was high.

    The South Fork compared well to a Coyote Meadow in CPM-10V at 62.5 HRC and had significantly higher edge retention slicing abrasive materials over a MEUK in 52100 at 57/59 HRC, a BlackJack small in 52100, and was significantly ahead of a Point Guard in 420J2 stainless at 54/56 HRC. The South Fork was also used to cut plywood and did not see the rapid edge degredation experienced by the small Sebenza for the same work. Again, the heat treatment of Reeve on S30V (and other steels) tends to produce differing results than standard, often not beneficial.

    The Chinook was showed significantly better edge retention (many to one) over a plain edged David Boat boat knife in cast Cobalt.

    The UK Pen was compared well to a K2 in D2 cutting carpet.

    There was little comparitative work done with the Dodo. The very unique blade shape makes direct comparions to other blades very difficult.

    The Manix had better edge retention than a Randall #1 in O1 (55/56 HRC) and another Randall #5 in 440B (56/57 HRC) both slicing cardboard and scraping wood. It also significantly outlasted a Meadowlark in C13CrMoV and a Point Guard in 420J2 and matched the performance of a small Sebenza in S30V slicing cardboard. In regards to corrosion resistance, cutting rhubarb which is highly acidic, the Manix had similar edge retention as the Randall #5 in 440B (56/57 HRC) and was significantly better than Randall #1 in O1 (55/56 HRC). The Manix also matched the performance of a Paramilitary in S30V on used carpet and both outcut a Heafner custom bowie in D2.

    The Paramilitary was used extensively on used carpet and the slicing edge retention was superior to be ahead ahead of a Agent in D2 and ahead of a Pacific Salt in H1. It was also compared to a Spyderco Catcherman in MBS-26 and Meadowlark in 8C13CrMoV and the Paramilitary outlasted both though the difference was small. As noted earlier with the Manix and Paramilitary were similar on wet used carpet and both outcut a Heafner custom bowie in D2, showing the effect of corrosion resistance.

    The Military was used for extensive edge retention work and found to have be comparable to the Temperance in VG-10 on hemp ropes, cardboard and used carpet.

    Summary : S30V is a powder metallurgy martensitic stainless steel made by Crucible. It has a high wear resistance which gives it high slicing edge retention on abrasive materials such as cardboard. Frequent problems with edge chipping have been reported frequently on online discussion forums, the performance was inconsistent in the blades used both in regards to edge retention and toughness. The optimal performance see was very high in regards to slicing aggression edge retention on some blades but the performance was consistent and durability problems were seen with both the small Sebenza and a Green Beret and there were issues with chipping during sharpening with a Benchmade Skirmish and RSK. In general, on the knives that worked well it showed a slightly increased performance in edge retention slicing abrasive materials, however careful observation had to be made to see a difference over other high carbide steels such as VG-10 and D2.

    S35VN : main

    S35VN was a response by Crucible to improve on the toughness and ease of machining/grinding S30V.


      • Carbon : 1.45%
      • Chromium : 14%
      • Molybdenum : 2%
      • Vanadium : 4%


    • Carbon : 1.4%
    • Chromium : 14%
    • Molybdenum : 2%
    • Vanadium : 3%
    • Niobium : 0.5%

    The main change was the removal of 1% Vanadium and addition of 0.5% Niobium. Niobium tends to form its own MC type carbides where Vanadium forms both MC carbides and dissolves in Chromium carbides. The use of Niobium to partially substitute for Vanadium thus increases the wear resistance and corrosion resistance. However as there was a 0.5% hard carbide loss then S35VN would be expected to have a slightly lower abrasive wear resistance.

    According to Crucibles data sheet has a 15-20% increase in toughness over S30V which would be expected given the slightly lower carbide volume (and carbon content). According to CATRA testing by Bohler is about 15% behind in low sharpness edge retention slicing abrasive paper (CATRA, silica) 1 which would be expected for the same reasons.

    Curiously enough, many early reports on S35VN knives reported issues with low edge strength including some dramatic failures such as the Sebenza exhibited in the video on the right where the entire edge bevel suffered catastrophic failure simply cutting rope. Unfortunately, as is often the case, the makers/manufacturers didn't always respond well to such complaints which tended to lower the perception of the steel to the general public.

    Knives used in S35VN :

    Mike's large flipper behaved very similar to other knives in S30V. A high carbide wear resistant stainless steel.

    Summary : S35VN is a powder metallurgy martensitic stainless steel designed by Crucible in a response by makers to improve grinability and impact toughness. These changes to performance are achieved by a slight reduction to the carbide volume

    Elmax : main

    Elmax is a third generation powder metallurgy steel made by Uddeholm, nominal composition :

    As shown in the graphs to the right, Elmax will have, depending on austenizing temperature :

    A similar steel, m390 / 20CV :

    Compared to m390, Elmax has a little less carbon, but also less Vanadium/Tungsten, and based on the general approximation/equation for carbon/vanadium balancing (adjust Vanadium by a multiplier of 0.18 to determine adjusted carbon content), it would be expected to have similar hardness (as it has similar carbon in solution). The lower chromium amount at the same effective carbon content and similar Molybdenum would promote less corrosion resistance, the lower vanadium would mean less wear resistance but better impact toughness than m390 both for the same reason, lower MC carbide volume. These properties are exactly what is seen in the literature :

    Pin on disk abrasion :

    • Elmax : 1975/500 F : 57 HRC : 62 mg
    • m390 : 2100/500 F : 59.5 HRC : 53 mg
    • S90V : 2150/500 F : 59 HRC : 52 mg
    • S110V : 2150/500 F : 59.5 HRC : 50 mg

    and :

    Steels such as alloy M390, Elmax and CPM420V achieve an impact energy between 30 and 45 J/cm2 over the full tempering range.


    The paper by Kershenbaur also contains corrosion and wear resistance data showing the relationship between Elmax and m390 as noted in the above.

    Knives personally used in Elmax :

    The Zero Tolerance blade had significant issues with edge retention and durability which have been reported frequently on ZT blades. The reporting was consistent enough that it caused a fairly negative perception of Elmax as a blade steel. Zero Tolerance also have in other cases noted that their heat treatment is secondary to other concerns such as aesthetics in the brazed line. While the knife performed poorly, given other reports and comments by ZT it likely isn't an indicator of the inherent performance of the steel.

    The Pretium showed very high edge retention slicing cardboard, among the best knives seen which would be expected given it was hardened for maximum strength and abrasion resistance. Ease of grinding was fairly low and it demanded high end stones to cut it well.

    Summary : Elmax is a well known plastic mould steel which combines a higher wear resistance and toughness (for that type of steel) and solid corrosion resistance (for a non-nitrogen steel). It is closely related to m390 being slightly less wear resistant and slightly tougher, but similar to m390 it is hard to argue for it as a blade steel over S90V aside from corrosion resistance. In fact more recent patents from Uddeholm such as WO 2002070769 A1, and WO2003069004A1 make this argument directly.

    m390/20CV/CTS-204p : main

    Nominal composition of m390 / 20CV / CTS-204p:

    M390 is a PM steel made by Bohler :

    Third generation powder metal technology. Developed for knife blades requiring good corrosion resistance and very high hardness for excellent wear resistance. Chromium, molybdenum, vanadium, and tungsten are added for excellent sharpness and edge retention. Can be polished to an extremely high finish. Hardens and tempers to 60-62 HRC.

    It has a very high wear resistance, comparable to S90V and S110V:

    Pin on disk abrasion :

    • Elmax : 1975/500 F : 57 HRC : 62 mg
    • m390 : 2100/500 F : 59.5 HRC : 53 mg
    • S90V : 2150/500 F : 59 HRC : 52 mg
    • S110V : 2150/500 F : 59.5 HRC : 50 mg

    In industry is commonly used a plastic mold steel and there is a significant body of literature on its material properties.

    Steels such as alloy M390, Elmax and CPM420V achieve an impact energy between 30 and 45 J/cm2 over the full tempering range.


    Interestingly enough, the same paper also shows the wear resistance to only be about half that of S90V but it uses the sand on drum method which uses a much larger and softer abrasive typically (50/70 mesh quartz). The pin on disk test as noted in the Crucible patent typically uses a smaller and harder abrasive, often silicon carbide. Vanadium carbide is hard enough to effectively cut into quartz but will wear similar to silicon carbide in contact and thus the drum measurement is much more sensitive to the vanadium carbide differences.

    Knives personally used in m390 :

    Unfortunately the Artifex knife came with a heat damaged edge and thus it tended to perform poorly (low ease of sharpening, edge holding and durability) which was likely due to issues with how it was ground.

    Summary : m390/20CV is a highly corrosion resistant stainless steel with a large carbide volume giving it a high wear resistance. However, it is hard to make an argument for it as a blade steel because S90V has similar toughness at a higher wear resistance and thus the only real advantage to m390 would be the higher corrosion resistance. In general there are few complaints about S90V in that regard but m390, Elmax and other steels are often used as plastic mold steels which can have severe corrosion requirements.

    CPM-S90V : main

    Nominal composition of S90V :

    S90V was a specific development point for Crucible as while it was a high vanadium stainless, similar to past steels such as S60V, S90V showed a particular focus in the type of carbide the steel was desired to form.

    ...whereby the resulting articles after hot working, annealing and hardening to 58 HRC, have a volume fraction of primary M7C3 and MC carbides of 16 to 36% in which the volume of MC carbides is at least one-third of the primary carbide volume and where the maximum sizes of the primary carbides do not exceed about six microns in their largest dimension

    This is achieved by reducing the chromium content to the minimum required for stainless (and hardenability) so as to minimize the amount of chromium carbide and instead focus on developing the much smaller and harder vanadium carbide. This produces a much higher balance of wear resistance when combined with toughness.

    As S90V has received interest as a bearing steel, there is significant materials data on it :

    Corrosion resistance (in mm/yer) when exposed to dilute aqua-regia

    • 440C : 1900/400 F : 58 HRC : 109 mm/hy
    • BG-42 : 2050/975 F : 63 HRC : 733 mm/hy
    • S90V : 2050/500 F : 58 HRC : 117 mm/hy
    • S90V : 2150/975 F : 62 HRC : 249 mm/hy
    • S125V : 2100/500 F : 61 HRC : 111 mm/hy
    • S125V : 2150/975 F : 58 HRC : 345 mm/hy

    Abrasion wear resistance (ASTM 132, pin on disk/3-micron abrasive) :

    • 440C : 1900/400 F : 58 HRC : 66 mg
    • BG-42 : 2050/975 F : 63 HRC : 41 mg
    • S90V : 2050/500 F : 58 HRC : 58 mg
    • S90V : 2150/975 F : 62 HRC : 37 mg
    • S125V : 2100/500 F : 61 HRC : 31 mg
    • S125V : 2150/975 F : 64 HRC : 22 mg

    Longitudinal impact toughness, C-Notch and bend fracture strength:

    • 440C : 1900/400 F : 58 HRC : 33 ft-lbs and 580 ksi
    • BG-42 : 2050/975 F : 63 HRC : 11 ft-lbs 507 ksi
    • S90V : 2150/975 F : 62 HRC : 19 ft-lbs and 630 ksi
    - Bearing Steel Technology, Issue 1419 : Wear and Corrosion Resistant PM Tool Steels for Advanced Bearing Applications, Kajinic, A, et. al.

    S90V shows similar corrosion resistance to BG-42, similar wear resistance and much higher toughness. Note this is also the best case scenario for wear resistance for BG-42, when the abrasive is larger, S90V will have improved relative performance. This can be seen when comparing S90V to m390 :

    Pin on disk abrasion (3 micron abrasive) :

    • Elmax : 1975/500 F : 57 HRC : 62 mg
    • m390 : 2100/500 F : 59.5 HRC : 53 mg
    • S90V : 2150/500 F : 59 HRC : 52 mg
    • S110V : 2150/500 F : 59.5 HRC : 50 mg

    S90V has similar wear resistance to m390, but much higher toughness :

    Steels such as alloy M390, Elmax and CPM420V achieve an impact energy between 30 and 45 J/cm2 over the full tempering range.


    However, when using a much larger abrasive (50/70 mesh quartz, rubber drum ASTM G65, S90V has twice the wear resistance of Elmax and m390. As the abrasive gets very fine, the relative wear resistance can improve for coarse carbide microstructures as the carbides themselves will undertake direct wear vs just resisting wear by ploughing Rodil .

    Knives personally used in S90V :

    The fillet knife was on loan and was not subject to extensive work. It was used extensively for filleting by a number of professional fisherman who did praise its initial edge retention however they had concerns about maintenance due to its not responding well to the traditional butchers steel.

    Summary : S90V is a powder metallurgy martensitic stainless steel having among the highest wear resistance for stainless steels and a corresponding low grindability, but having similar toughness to conventional high carbide steels such as ATS-34 .

    S110V : main

    Nominal composition of S110V :

    Note the very high carbon content, very high amount of strong carbide formers (vanadium and niobium) which produces the very high volume of carbide shown in the image at the right. The chromium is kept to a minimum (similar to S90V) to ensure that chromium carbide (which is a softer/larger carbide) is kept to a minimum as it has a low toughness/wear resistance gain compared to vanadium/niobium carbide.

    S110V was introduced in 2005 :

    2005 - Developed stainless tool steel CPM S110V for enhanced corrosion resistance

    It is a further development of high wear high corrosion resistant steels (the 420V family) which were covered in an earlier patent EP 0773305 B1 . The patent for S110V EP 1721999 a1 describes the advancement of this steel which includes the main modifications over the very high vanadium steels previously used (S125V) to :

    The niobium produces a higher free chromium and produces smaller and finer carbides than vanadium. The cobalt keeps the ferrite out of the final as-quenched form and thus preserves the strength of the steel. Interestingly enough, in 2010 the data sheet for S110V was changed and now lists new nominal values in the composition 2010 vs the original sheet in 2008 2008 .

    As a point of comparison :


    • Carbon : 2.3%
    • Chromium : 14%
    • Molybdenum : 1.0%
    • Vanadium : 9.0%


    • Carbon : 2.8%
    • Chromium : 14%
    • Cobalt : 2.0%
    • Molybdenum : 3.5%
    • Vanadium : 9.0%
    • Niobium : 3.5%

    S125V / VIM CRU 60:

    • Carbon : 3.3%
    • Chromium : 14%
    • Cobalt : 0.25%
    • Molybdenum : 2.5%
    • Vanadium : 11.85%
    • Tungsten : 0.25%
    • Manganese : 0.25%
    • Nickel : 0.2%

    Note compared to S90V, S110V has significantly more carbon and carbide formers to produce a higher wear resistance and maintain a high working hardness. However it has a reduced carbon content compared to S125V and a similar alloy carbide amount and thus would be expected to have a slightly lower working hardness. This is found in the materials data in the patent.

    The patent contains wear resistance data :

    Pin on disk abrasion :

    • Elmax : 1975/500 F : 57 HRC : 62 mg
    • m390 : 2100/500 F : 59.5 HRC : 53 mg
    • S90V : 2150/500 F : 59 HRC : 52 mg
    • S90V : 2150/975 F : 61.5 HRC : 37 mg
    • S110V : 2150/500 F : 59.5 HRC : 50 mg
    • S110V : 2150/975 F : 62.5 HRC : 34 mg

    This shows no significant in wear resistance between m390, S90V and S110V with similar hardening, Elmax has a slightly lower wear resistance. Unfortunately the data for Elmax isn't presented for secondary hardening as it has a very strong secondary hardening response.

    The patent also has corrosion resistance data but it is the calculated PRE, it isn't the result of actual tests showing the material loss in corrosive environments.

    Note that in comparison, S125V has significantly higher wear resistance than S90V in the same standard test :

    Abrasion wear resistance (ASTM 132) :

    • S90V : 2150/975 F : 62 HRC : 37 mg
    • S125V : 2150/975 F : 64 HRC : 22 mg
    - Bearing Steel Technology, Issue 1419 : Wear and Corrosion Resistant PM Tool Steels for Advanced Bearing Applications, Kajinic, A, et. al.

    which would be expected given the higher hardness and carbide volume. Comparing both sources, the wear resistance of S110V would be lower than S125V.

    Knives used in S110V :

    The Modulator was compared to other knives slicing cardboard and found to have mid to high edge retention, possibly suffering from carbide tear out. The edge in general tended to be very chippy and would fracture readily. The grindability was also very low and tended to require specialized stones in order to sharpen it effectively.

    S125V : main

    Nominal composition of S125V / VIM CRU 60:

    S125 was introduced in 2004 :

    2004 - Developed stainless tool steel CPM S125V for improved corrosion and wear resistance.

    It is very similar to a family of high wear, corrosion resistant alloys covered in an early patent EP 0773305 B1 aside from the small amount of Cobalt. There does not appear to be a specific patent on S125V introducing the small amount of Cobalt though it is added in the patent for S110V EP 1721999 A1 which used a much higher amount of Cobalt to keep ferrite out of the as-tempered steel and also also includes the partial substitution of Niobium for Vanadium.

    In regards to the alloy content, the very high carbon content allows for a very high as-tempered hardness up to 64/66 HRC and combined with the very high vanadium produces a large volume of MC type carbides. The chromium is balanced at a minimum amount just necessary to produce high corrosion resistance to ensure that the bulk of the carbide is non-chromium (as those as larger and softer carbides). The large amount of Molybdenum also promotes the secondary hardening and increases corrosion resistance in regards to pitting and crevice corrosion. Note the image at the right showing the very large amount of carbide compared to 440C, BG-42 and even S90V.

    As these steels can be used for bearing applications, a common use of 440C, there is a wealth of materials data on such steels :

    Corrosion resistance (in mm/yer) when exposed to dilute aqua-regia

    • 440C : 1900/400 F : 58 HRC : 109 mm/hy
    • BG-42 : 2050/975 F : 63 HRC : 733 mm/hy
    • S90V : 2050/500 F : 58 HRC : 117 mm/hy
    • S90V : 2150/975 F : 62 HRC : 249 mm/hy
    • S125V : 2100/500 F : 61 HRC : 111 mm/hy
    • S125V : 2150/975 F : 58 HRC : 345 mm/hy

    Abrasion wear resistance (ASTM 132) :

    • 440C : 1900/400 F : 58 HRC : 66 mg
    • BG-42 : 2050/975 F : 63 HRC : 41 mg
    • S90V : 2050/500 F : 58 HRC : 58 mg
    • S90V : 2150/975 F : 62 HRC : 37 mg
    • S125V : 2100/500 F : 61 HRC : 31 mg
    • S125V : 2150/975 F : 64 HRC : 22 mg

    Longitudinal impact toughness, C-Notch and bend fracture strength:

    • 440C : 1900/400 F : 58 HRC : 33 ft-lbs and 580 ksi
    • BG-42 : 2050/975 F : 63 HRC : 11 ft-lbs 507 ksi
    • S90V : 2150/975 F : 62 HRC : 19 ft-lbs and 630 ksi
    - Bearing Steel Technology, Issue 1419 : Wear and Corrosion Resistant PM Tool Steels for Advanced Bearing Applications, Kajinic, A, et. al.

    Unfortunately the bend fracture strength of S125V, and impact toughness of the steels was not determined.

    In short :

    S125V was used for cutlery for a short period of time and even though there was some interest due to the very high abrasion resistance, which is even significantly higher than S90V. There were issues with durability and grindability. These were so extreme that even makers who specialized in high carbide steels were not that positive about the steel :

    The workability is very low in fact; I have had trouble with a few blades cracking with the result of lost time and wasted abrasive. It has such a high percentage of alloy that at optimum hardness (65/66) even with a very thin edge it is difficult to sharpen. Given all of this, I have decided to drop it from my offerings of blade steel.

    There were some positive results such as the CATRA results from Spyderco which show it among the highest steels they have reported :

    • 440C : 360-400
    • VG10 : 500-510
    • S30V : 550-580
    • S90V : 750
    • ZDP 189 : 750
    • S125V : 1200

    It would be nice in those comparisons though to have a little more detail about how the knives were hardened.

    Knives used in S125V :

    The knife was found to be similar in VG-10 in regards to corrosion resistance and had light spotting in extended exposure to salt water. The edge retention in slicing carbide was found to be compromised, likely due to the very high carbide volume passing the point of being a benefit. The grindability was found to be very low compared to similar steels by comparing the number of passes required to sharpen after cutting sods.

    ZDP-189 : main

    ZDP-189 is a powder metallurgy stainless steel made by Hitachi Metals of Japan. The actual composition of the steel is unkown publically as Hitachi has described it as 3C20CrMoW, thus the molybdenum and tungsten amounts are unknown. Cowry X is a similar steel made by the Daido Corporation which also has the same carbon and chroimum content but also contains 0.3% vanadium and 1% molybdenum so ZDP-189 may have similar amounts of molybdenum and tungsten raplacing the vanadium as those two have similar effects. While the large amount of primary carbides would seem to suggest issues with sharpness the only problems reported are with sharpening on ceramic rods which can in general cause issues with high hardness steels. In general feedback from user on sharpeness and sharpness is high. Materials data on ZDP-189 :

    Promotional material from makers/manufacturers :

    Knives personally used in ZDP-189 :

    There have been some comments about problems with sharpening of ZDP-189 on ceramic rods, however feedback from user with waterstones typically praising ease of obtaining a high sharpness. Comments have been made about edge damage on ZDP-189 through edge pitting and other reports of corrosion. There have also been some issues with chipping in light cutting but the frequency of reports is very low, especially to S30V.

    The ZDP-189 Delica was compared to the VG-10 Delica on slicing 1/8" cardboard through 4 centimeters of edge and found to have significantly better early edge retention and a small advantage in extended use. This was repeated with a 1200 DMT finish on 1/4" cardboard and the ZDP-189 Delica had again significantly better early edge retention and a more significant advantage in extended use. All three Spyderco ZDP-189 blades were compared to multiple S30V blades and the ZDP-189 knives were found to on average cut 57 (8) % more cardboard than the S30V blades before reaching a similar level of blunting.

    Summary : ZDP-189 is a powder metallurgy martensitic stainless steel made by Hitachi Metals. ZDP-189 is mainly promoted for the very high hardness 66/67 HRC which is rare in staniless steels.

    Talonite : main

    Talonite is a cobalt super-alloy, it has the same composition as Cobalt 6BH which is further hot roll and age hardened. It is very soft, 42-47 HRC, and has yield and tensile points of 121 and 195 kpsi respectively. For reference Mission's Beta Ti has a yield sterngth of 230 kpsi at 47 HRC and the tensile strength of A2 at 57/58 HRC is 310 kpsi.

    Composition of Talonite
    Cobalt Balance
    Nickel 3% max
    Silicon 2% max
    Iron 3% max
    Manganese 2% max
    Chromium 28%-32%
    Molybdenum 1.5% max
    Tungsten 3.5%-5.5%
    Carbon 0.9%-1.4%

    Manufacturer data on Talonite from Carbide Processors:

    A reference page on Talonite by Marion Poff :

    Unfortunately most of the Bladeforums links are broken due to alterations in the way links are archived due to software changes. They can however be retrived with use of the Internet Archive data base.

    Knives personally used in Talonite :

    The MEUK was compared to ATS-34 and VG-10 (59/60 HRC) F1's from Fallkniven and a D2 custom (62 HRC) from Mel Sorg and the Talonite blade was found to be immune to a strong salt water solution which left the steel blades significantly blunted and required extensive honing to restore : ref. The Talonite MEUK was also compared to several other steel blades on cardboard at three different finishes, polished, medium and coarse. Talonite was able to match the performance of a VG-10 F1 from Fallkniven when both had medium finishes but was vastly outcut by a CPM-10V custom (62.5 HRC,full cryo) with fine polishes and a D2 custom (62 HRC) with a rough finish : ref. The MEUK was also used to cut various metals alongside a VG-10 and ATS-34 F1 and in general it took more damage and took much longer to sharpen : ref.

    Summary : Talonite is useful as a blade material when very high corrosion resistance is desired. However the edge retention on cardboard was very low compared to tool steels (D2 and 10V), and the durabiity and sharpening time poor compared to high carbon stainless steels (ATS-34 and VG-10) cutting harder materials. No benefits were seen due to the promoted "lubricity" of talonite nor of its ability to retain aggression after losing a "razor edge", it fared worse than quality steels in that regard. Blunting of course is nonlinear in general so the rate of edge degredation slows down with any blade material with use.

    LM1 : main

    LM1 is an amorphous (no specific crystal structure) alloy of titanium, copper, nickel, zirconium and beryllium. It can be cast to a very precise shape.

    This document shows a very low yield strength, 220 ksi, much lower than hardened cutlery steel, and a low hardness, about 50 HRC, and fairly brittle nature. The density is also much lower than steel, 6.3 g/cm^2 vs 7.8-8.1^3.

    Knives personally used in LM1 :

    The model 10 was used for a large variety of work with the edge retention examined on hemp, cardboard, carpet and woods. In all cases it was well behind cutlery steels, even low grade ones, with the edge retention on hemp being just a fraction of a Swiss Army knife (ref) and a regular Olfa knife readily outclassed it on cardboard (ref). The durability was also very low as it chipped out consistently during wood chopping and this was a very light blade (ref). On harder work, light metals, bone and some light impacts on concrete, the LM1 blade was well behind various cutlery steels (ref). In regards to sharpening, there were no significant difficulties associated with this particular material, the only note of interest it that it didn't tend to benefit as much from more coarse finishes as steel blades do, probably because it doesn't have the strength and durability to hold the micro-teeth.

    Summary : LM1 is a very corrosion resistant blade material, however it is much softer, weaker and more brittle than even the lower end cutlery steels and thus has much lower edge retention, durability and optimal cutting ability because it needs thicker profiles to gain the necessary durability.

    Titanium - 6AL4V : main

    As a point of general consideration about Titanium, it is very expensive to make compared to steel, roughly an order of magnitude because of the extreme stability of the base mineral/oxide it is extracted from. This is why Titanium is rarely used compared to steel even though it has a very high strength/weight ratio.

    Nominal composition of 6Al4V :

    This is the most common form of Titanium used in knives which is an alloy of Titanium to allow it to be heat treatable and form martensite similar to steel is an alloy of iron with other elements for similar reasons. This particular alloy of Titanium is also classified as Titanium Grade 5 and it one of the most commonly used Titanium grades.

    Pure titanium undergoes an allotropic transformation from the hexagonal close-packed alpha phase to the body-centered cubic beta phase at a temperature of 882.5C (1620.5F). Alloying elements can act to stabilize either the alpha or beta phase. Through the use of alloying additions, the beta phase can be sufficiently stabilized to coexist with alpha at room temperature. This fact forms the basis for creation of titanium alloys that can be strengthened by heat treating.

    In 6Al4V, the aluminum is an alpha stabilizer and raises the alpha to beta transition temperature. Vanadium is a beta stabilizer and causes the retention of the beta phase at room temperature. How it is hardened is very similar to steel, and just as in steel it is critical to ensure that the way it is hardened is chosen to generate the desired properties. For example high toughness is optomized at a different sub-structure than fatigue.

    The properties of titanium are the high strength/weight ration, very high corrosion resistance, bio-compatability, non-magnetic and high toughness/ductility. Specific to the latter, just as in steels the toughness and strength are effected by how it is hardened :

    • As quenched from 900 C : Charpy V-notch = 10 J
    • As quenched from 980 C : Charpy V-notch = 5 J

    These toughness values are at the typical working hardness values up to 47 HRC and a UTS (ultimate tensile strength) of 1125 MPa. For reference, the annealed toughness :

    As a point of comparison, high toughness tool steel such as S7, at a similar hardness, 45 HRC will have a similar yield strength (1380 MPa CYS). However it can achieve much higher strength values (2070 MPA, CYS at 57 HRC). The strength / toughness ratio is also higher as it can have a charpy V-notch toughness of 17 J at a hardness of 57 HRC Matweb. Steels such as S7 are thus able to have similar or greater toughness values than such Titanium alloys as used in cutlery.

    Knives personally used in Ti 6Al4V:

    The Mission MPK-Ti was significantly softer than most steel knives and would commonly dent/deform easier, the serrations even bent chopping a piece of seasoned wood for example. However, it takes a very tough blade to be able to handle the severe impacts (up to metal on metal) that it could take without gross damage, something like the ESEE line for example. In regards to edge retention, the serrations did very well, but the plain edge is very low even compared to basic steels. It is also fairly gummy, can be difficult to clean off of ceramic sharpening stones and requires significant burr removal to form a very sharp edge.

    The Shikra was found to be very similar to the MPK in most respects. It is carbidized with Tungsten carbide, however this does little to increase the edge strength or durability. However if cutting is willing to be done at very low sharpness then it will essentially self-sharpen in extended use as the Titanium wears away forming a lip of tungsten carbide which does the cutting. However this coating is fairly thick compared to a sharpened steel blade and so again, the sharpness in that state is fairly low, i.e., it can slice stiff papers at most.

    Summary : unless the low density of Titanium is utilized (increase the cross section, as weight scales with thickness, strength is quadratic in thickness), or the novel abilities of Titanium are required (non-magnetic), given the fact that there are tough and almost corrosion immune stainless steels (H1 for example), it is difficult to see Titanium alloys such as 6Al4V being used over stainless steels aside from very niche applications.

    Comments and references : main

    Comments can be emailed to cliffstamp[REMOVE]

    Last updated : 02 : 10 : 2015
    Originally written: 01 : 05 : 2006