CPM S90V Knife Steel: Edge Retention, Toughness & Comparisons

CPM S90V is one of the highest-edge-retention stainless knife steels in common use, but that alone is not what makes it interesting. S125V can push edge retention even further. MagnaCut is dramatically tougher. M390 and S110V offer stronger corrosion resistance. SG2 is easier to process. S90V matters because of where it sits between those extremes.

This page looks at S90V as a steel, separately from any particular knife made from it. The goal is to bring the useful data into one place, explain what the numbers actually mean, and make comparisons that are useful both to people buying knives and to people making them.

What is CPM S90V steel?

CPM S90V is a powder-metallurgy martensitic stainless steel originally developed by Crucible. It was introduced under the name CPM 420V and was later renamed CPM S90V.

Its defining feature is approximately 9% vanadium. That unusually high vanadium content produces a large amount of very hard vanadium carbide, giving S90V exceptional abrasive wear resistance and slicing edge retention.

This is an important distinction because hardness alone does not determine edge retention. Two blades can have the same Rockwell hardness and still differ greatly in wear resistance depending on what carbides are present, how much carbide exists, how large those carbides are, and how the steel was heat treated.

S90V is therefore not simply “a 62 HRC steel” or “a super steel.” It is a specific metallurgical approach: a stainless matrix combined with a large volume of hard vanadium carbides, made practical through powder metallurgy.

S90V composition and why the chemistry matters

One of the clever parts of the S90V design is that it does not simply maximize chromium. Niagara Specialty Metals explains that the high vanadium content favors hard vanadium carbides rather than relying mainly on chromium carbides for wear resistance. This leaves enough chromium in the steel matrix to provide useful corrosion resistance while allowing vanadium carbide to do much of the wear-resistance work.

That is why comparing steels by carbon percentage, chromium percentage or HRC alone is often misleading. The type, quantity and distribution of carbides can matter just as much as the headline chemistry.

Primary source: Niagara Specialty Metals – CPM S90V technical data sheet.

S90V compared with other knife steels

The ratings below use the public comparative scale published by metallurgist Dr. Larrin Thomas at Knife Steel Nerds. Keeping all steels on one rating system is more useful than mixing CATRA percentages, Charpy values, manufacturer claims and anecdotal impressions from unrelated tests.

Data note: SG2 toughness was directly tested by Knife Steel Nerds, but its edge-retention rating is based on a metallurgical estimate rather than a direct CATRA result. SPG STRIX is intentionally absent because there is not yet comparable independent edge-retention and toughness data. MagnaCut is shown at the published rating of 7 for toughness so that the table remains internally consistent; newer 2026 testing of Erasteel-produced MagnaCut showed improved toughness compared with earlier Crucible material.

Rating source: Knife Steel Nerds – Knife Steels Rated by a Metallurgist.

Knife steel edge retention comparison

Edge retention is where S90V separates itself from familiar premium kitchen steels. On the Knife Steel Nerds scale it sits just below S125V and above S110V, ZDP-189, M390, HAP40, SG2, MagnaCut and VG10.

Comparative rating scale from Knife Steel Nerds. Higher is better. The values are not percentages and should not be interpreted as linear multiples of one another. Visualization by Hikari Chef Knives from the published numerical ratings.

What does “edge retention” mean here?

Knife Steel Nerds uses CATRA slicing tests as a major source of edge-retention data. CATRA repeatedly cuts standardized abrasive test media with controlled knife geometry and records how much material is cut before the edge loses performance. It is particularly useful for comparing abrasive wear resistance.

But CATRA is not “how long this knife will stay sharp in your kitchen.” A finished knife can dull through abrasive wear, deformation, microchipping or corrosion. Edge angle and geometry can also change cutting life enormously. Knife Steel Nerds has shown that sharpening angle alone can produce differences large enough to overwhelm many steel-to-steel differences.

This is why a rating of 9 for S90V should be read as “exceptionally high abrasive slicing edge retention when compared on similar terms,” not as a promise that every S90V knife will stay sharp twice as long as every knife rated 4.5.

Knife steel toughness comparison

Toughness measures resistance to fracture. In a knife, insufficient toughness can contribute to chipping or cracking when an edge is stressed beyond what its geometry can tolerate.

Comparative toughness ratings from Knife Steel Nerds. These are steel-property ratings, not a prediction of which finished knife will chip first. Visualization by Hikari Chef Knives from the published numerical ratings.

S90V is not a high-toughness steel in absolute terms. The interesting result is that it retains more toughness than might be expected for a steel with such extreme wear resistance. In this comparison, S125V, S110V and ZDP-189 all fall below it on toughness, while only S125V exceeds it on edge retention.

That is the real S90V story. It does not escape the normal tradeoff between wear resistance and toughness. It simply occupies a particularly useful point at the extreme edge-retention end of that tradeoff.

What the steel ratings really mean

The Knife Steel Nerds ratings are not arbitrary internet scores, but they are also not raw laboratory units. They consolidate CATRA testing, standardized toughness testing, hardness behavior and metallurgical estimates into a single comparison scale.

For most steels, the ratings represent approximately the 59-62 HRC region, with exceptions for steels that are rarely used at those hardnesses. The purpose is to show the general property balance of a steel, not every possible heat treatment.

The scale is also deliberately coarse. A toughness score of 4 for two steels does not mean their measured toughness is identical. A score of 9 versus 4.5 for edge retention does not mean exactly twice the cutting life. Differences at the low end of toughness can also be more significant than the simple bar length makes them look.

S90V vs S125V – why not just use S125V?

S125V is the obvious alternative if maximum abrasive edge retention is the only target. Knife Steel Nerds rates it at 9.5 for edge retention versus 9 for S90V.

The cost is toughness. S125V drops to 2.5 versus 3.5 for S90V. It also contains an even larger carbide volume and has a reputation for being exceptionally difficult to manufacture, grind and finish.

Knife Steel Nerds’ dedicated testing found that S125V gains edge retention but gives up toughness and workability compared with S90V. In practical terms, S125V moves further toward the extreme end of the same tradeoff for a relatively small increase in edge-retention rating.

For a knife that is supposed to be used rather than simply maximize one laboratory property, S90V can therefore be the more attractive balance.

Detailed testing: Knife Steel Nerds – S90V and S125V.

S90V vs S110V – which is better?

S110V was developed later and places more emphasis on corrosion resistance. It uses both vanadium and niobium carbides and has a more corrosion-oriented alloy design.

On the Knife Steel Nerds scale, however, S90V scores higher in both edge retention and toughness: 9 versus 8 for edge retention and 3.5 versus 3 for toughness. S110V’s advantage is corrosion resistance.

Even Dr. Larrin Thomas has noted that S110V scoring below S90V in CATRA is not the result one would intuitively expect from composition alone, but it is what the test produced. That is an important reason to keep experimental results separate from what a steel “should” do on paper.

Choose S90V when extreme edge retention and the better toughness balance matter more. Choose S110V when very high edge retention is still required but corrosion resistance has greater priority.

Source: Knife Steel Nerds – CPM S110V history and properties.

S90V vs ZDP-189 – edge retention, toughness and sharpening

ZDP-189 is one of the most relevant comparisons for Japanese kitchen knives because it is famous for very high hardness and long edge life. Yet the metallurgy is quite different.

Knife Steel Nerds measured ZDP-189 at 162% in CATRA relative to its 440C reference and found it below S90V. The explanation is not simply hardness. ZDP-189 has a very large amount of chromium carbide, while S90V gets more wear resistance from much harder vanadium carbide.

ZDP-189 does have a sharpening advantage that is often overlooked. Chromium carbides are softer than aluminum oxide, so conventional Japanese waterstones can abrade them effectively. S90V’s vanadium carbides are harder than aluminum oxide, making diamond or CBN a more efficient abrasive choice.

So S90V is not “better at everything.” It offers the stronger toughness-edge-retention balance and better corrosion resistance, while ZDP-189 remains attractive for very high hardness and compatibility with conventional waterstones.

Source: Knife Steel Nerds – ZDP-189 and Cowry-X.

S90V vs M390 – why does S90V hold an edge longer?

M390, 20CV and 204P are often treated as a family because their compositions and properties are very similar. They are excellent high-alloy PM stainless steels and are particularly strong in corrosion resistance.

On the Knife Steel Nerds rating scale, M390 scores 6.5 for edge retention versus 9 for S90V. Both are rounded to 3.5 for toughness in the public table.

That equal 3.5 toughness score should not be interpreted as laboratory identity. Knife Steel Nerds’ dedicated S90V work describes S90V as having a superior toughness-edge-retention balance and reports it as tougher than M390 in the relevant comparison. The public rating system intentionally compresses many measurements into broad half-point steps.

The practical choice is therefore straightforward. M390 makes sense when excellent corrosion resistance and high wear resistance are the priority. S90V makes sense when significantly more slicing edge retention is worth more difficult grinding and sharpening.

S90V vs MagnaCut – two completely different design goals

MagnaCut and S90V are useful to compare precisely because neither makes the other obsolete.

S90V scores 9 for edge retention and 3.5 for toughness. MagnaCut scores 5 for edge retention and 7 for toughness on the published Knife Steel Nerds scale. MagnaCut also has excellent corrosion resistance and a very fine carbide structure.

This means S90V is the obvious choice when long abrasive slicing edge life is the main goal. MagnaCut is the more logical choice when toughness, edge stability and tolerance for thin geometry or impact matter more.

That difference is especially important for kitchen-knife design. A fine slicer can benefit from S90V’s wear resistance. A chopping knife or cleaver benefits much more from MagnaCut’s ability to combine high hardness with substantially greater toughness.

Knife Steel Nerds specifically points out that MagnaCut’s toughness allows thinner or more acute edges with less susceptibility to chipping and that it is suitable for everything from thin kitchen knives to large chopping knives.

Source: Knife Steel Nerds – CPM MagnaCut.

S90V vs HAP40 – stainless wear resistance vs high-speed steel

HAP40 is the Japanese designation for the high-speed-steel grade also sold as Rex 45 and related equivalents. Knife Steel Nerds rates HAP40 / Rex 45 at 6 for edge retention and 4.5 for toughness.

HAP40 can be used at very high hardness and has somewhat more toughness than S90V, but it is not stainless. S90V offers much greater abrasive edge retention together with genuine stainless corrosion resistance.

For kitchen knives, HAP40 remains attractive to users who like very high hardness and do not mind caring for a reactive core. S90V is attractive when the goal is still higher slicing edge life without giving up stainless behavior.

Source: Knife Steel Nerds – Rex 45 / HAP40 edge-retention testing.

S90V vs SG2 – is S90V simply a better SG2?

No. SG2 and S90V occupy different points on the same general PM-stainless spectrum.

SG2 is rated at 5 for edge retention and 4 for toughness. S90V is 9 for edge retention and 3.5 for toughness. S90V therefore gives a very large increase in wear resistance for a relatively modest reduction in the comparative toughness rating.

The cost is workability. SG2 contains far less wear-resistant carbide and is easier to grind, finish and sharpen. It is also a very established steel in Japanese kitchen-knife production.

There is another methodological point: Knife Steel Nerds directly tested SG2 toughness, but its edge-retention value was estimated from composition and carbide content rather than measured in CATRA. The score is still useful as a comparative estimate, but it should not be presented as a direct laboratory result.

Source: Knife Steel Nerds – VG10 and Super Gold 2.

Is VG10 really tougher than SG2?

This is a good example of why internet reputation and steel-property testing can appear to disagree.

Knife Steel Nerds heat treated VG10 and SG2 to almost exactly the same hardness, approximately 60.7 HRC, and tested both with the same subsize unnotched Charpy method. VG10 averaged 5.8 ft-lb. SG2 averaged 6.5 ft-lb.

In that controlled test, SG2 was not less tough. It actually measured slightly higher, although the two steels were close enough that the broader Knife Steel Nerds rating system rounds both to a toughness score of 4.

Why, then, do many users associate SG2 knives with chipping?

Because steel toughness is only one part of chip resistance. A finished knife can be harder, thinner behind the edge, sharpened at a more acute angle, or simply used for a different purpose. Any of those changes can make the finished knife less tolerant of lateral stress even if the underlying steel has similar measured toughness.

Takefu’s own material also lists VG10 at HRC 60 or higher and SG2 at HRC 62 or higher, reinforcing the point that the steels are commonly intended for different hardness ranges. A harder SG2 knife can therefore behave differently from a softer VG10 knife without contradicting the controlled toughness data.

Sources: Knife Steel Nerds – VG10 and SG2 testing and Takefu Special Steel – Super Gold 2.

Where does SPG STRIX fit compared with S90V, ZDP-189 and SG2?

SPG STRIX is interesting precisely because it takes a different approach from carbide-heavy powder steels. Takefu describes STRIX as a matrix-strengthened stainless powder steel designed to reach approximately 65 HRC while remaining unusually easy to grind and sharpen.

Takefu’s explanation is that conventional high-hardness powder steels rely heavily on very hard carbide particles, while STRIX obtains more of its hardness from the metallic matrix itself. The company says this reduces the sharpening difficulty normally associated with high-hardness PM steels and gives STRIX sharpening behavior closer to carbon steel.

That makes STRIX highly relevant to a modern kitchen-steel comparison, but there is a problem: we do not yet have comparable independent numbers.

STRIX vs ZDP-189 – does STRIX hold an edge longer?

We do not know yet. Any precise ranking would be invented.

The metallurgy does give us a reasonable direction, but it should be labeled as an inference. ZDP-189 achieves very high wear resistance through a very large carbide volume and has a Knife Steel Nerds edge-retention rating of 8. Takefu says STRIX deliberately reduces dependence on the very hard carbides that make conventional high-hardness PM steels difficult to sharpen and instead strengthens the matrix.

That makes lower CATRA-style abrasive edge retention than ZDP-189 or S90V a reasonable expectation, but not a measured conclusion. STRIX’s high matrix hardness could narrow some of that gap. Until comparable independent testing exists, we will not assign STRIX a numerical score or place it on the charts.

It is also plausible that STRIX is easier to sharpen than ZDP-189 despite similar very high hardness, because ease of sharpening is affected by carbide type and volume as well as HRC. Again, there is no standardized head-to-head test yet, so this should not be presented as a measured fact.

STRIX vs SG2

Takefu lists SG2 at HRC 62 or higher and STRIX at about HRC 65. The design direction is different: SG2 is the established high-alloy PM stainless, while STRIX is explicitly designed to obtain very high hardness with less sharpening resistance from hard carbides.

Until independent testing arrives, the useful conclusion is not “STRIX is better than SG2.” It is that STRIX appears to target a different compromise: higher matrix hardness and easier sharpening at that hardness, while SG2 has a much larger body of real-world history and independent comparative data.

Primary sources: Takefu Special Steel – SPG STRIX and Takefu original blade-steel specifications.

S90V hardness – why do some sources say 56-59 HRC while knives are 62+?

This is one of the most confusing things people encounter when researching S90V.

Niagara Specialty Metals’ general S90V data sheet lists an aim hardness of HRC 56-59. Knife Steel Nerds, however, demonstrates that S90V is capable of much higher hardness and reports approximately 66 HRC as achievable with suitable knife-oriented heat treatment. In its test program, an S90V CATRA knife using a 2050°F austenitize and low-temperature temper measured about 61.7 HRC.

There is no contradiction. A manufacturer’s broad industrial data sheet is not a statement of the maximum hardness the alloy can reach, nor is it automatically the optimum target for a thin kitchen knife. Tooling applications may prioritize dimensional stability, toughness, corrosion or processing differently from cutlery.

For knife buyers, the useful lesson is that HRC must be interpreted together with the steel and geometry. For knifemakers, it means the heat-treatment target should be chosen for the actual knife rather than copied from a generic material-data-sheet number.

Sources: Niagara S90V data sheet and Knife Steel Nerds S90V heat-treatment testing.

Does higher HRC automatically mean better edge retention?

No. Hardness improves strength and generally increases wear resistance, but HRC does not tell you what carbides are present or how much carbide exists. This is why S90V at a moderate knife hardness can outperform a much harder steel in abrasive edge retention.

HRC is also not toughness. A softer edge may deform rather than chip, which can create the impression that it is “tougher” even when the failure mode is simply different.

Is S90V hard to sharpen?

S90V has a reputation for difficult sharpening because its vanadium carbides are harder than aluminum oxide, the abrasive used in many conventional waterstones, belts and sandpapers. Knife Steel Nerds recommends diamond or CBN abrasives when efficient material removal is required.

That does not mean routine edge maintenance is necessarily difficult. There is an important difference between repairing damage or reprofiling an S90V edge and simply refreshing an existing edge that has lost some of its sharpness.

How long does it take to refresh an S90V edge?

To make this less theoretical, we timed a routine edge refresh on a BTN CPM S90V chef’s knife using a #10,000 Japanese waterstone. The first video shows the touch-up with the timer running. The second shows the knife cutting after the touch-up.

Timed S90V edge touch-up

A routine edge refresh on a #10,000 Japanese waterstone. This is not repair of a damaged edge or a major reprofiling.

Cutting tomtao after the touch-up

A practical cutting demonstration immediately after the touch-up. This is not a standardized sharpness measurement.

In our own experience with S90V kitchen knives around 62 HRC, routine sharpening has been considerably more manageable than the steel’s reputation might suggest. We treat this as practical experience rather than standardized testing. For major edge work, diamond or CBN still makes the process faster and more predictable.

Why can ZDP-189 feel easier to sharpen even when it is harder?

Because Rockwell hardness measures the steel as a whole, not the hardness of individual carbides. ZDP-189 is dominated by chromium carbides, which aluminum oxide can abrade. S90V contains a large amount of vanadium carbide, which is harder than aluminum oxide. This is a good example of why HRC alone cannot predict sharpening behavior.

How corrosion resistant is S90V?

S90V is genuinely stainless and offers useful corrosion resistance, but it is not the corrosion-resistance champion of modern PM steels. Knife Steel Nerds describes it as roughly middle of the road among stainless knife steels and below S110V and M390 / 20CV in corrosion resistance.

For normal kitchen use, good care is still simple: wash the blade, do not leave acidic or salty food on it for long periods, and dry it after use. “Stainless” should never be interpreted as “cannot stain.”

Which steel should you choose when buying a knife?

There is no single best knife steel. The right question is what failure mode or maintenance burden you care about most.

The steel name should never be the only reason to buy a knife. A well-heat-treated SG2 knife with excellent geometry can be a better cutter than a poorly designed S90V knife. Steel gives the maker a set of possibilities; the finished knife determines how well those possibilities are used.

Notes for knifemakers considering S90V

1. Expect slow grinding and finishing

S90V’s wear resistance does not disappear because the steel is being made into a knife. Niagara describes its machinability and grindability as more difficult than D2 or 440C and recommends appropriate high-performance abrasives. Hand finishing will also take more time than with lower-wear steels.

2. Use the right sharpening and grinding abrasives

For the final edge, diamond and CBN are the most efficient choices because they are harder than vanadium carbide. Conventional abrasives can still work, but the difference becomes more obvious as the amount of steel being removed increases.

3. Do not chase hardness as a number by itself

S90V can reach very high hardness, but the best target depends on blade geometry and use. Increasing hardness can improve strength and edge retention while reducing toughness. A thin kitchen knife and a heavy utility knife should not automatically receive the same target simply because the alloy name is the same.

4. Geometry can matter more than the steel comparison

Toughness determines how much freedom a maker has to use thin or acute geometry without chipping, but geometry itself remains a major control. A tougher steel can support a thinner edge; a lower-toughness steel can still be durable when given more conservative geometry.

5. S90V is not the right answer for every knife

If the design is a heavy chopper, cleaver or knife expected to see impact, MagnaCut or another significantly tougher steel can be the more rational choice. If maximum corrosion resistance is the priority, S110V or M390 may make more sense. If easy hand finishing is central to the project, S90V imposes a real production cost.

So why choose S90V?

Because its property balance is unusual at the extreme edge-retention end of the spectrum.

S90V does not have the toughness of MagnaCut. It does not have the corrosion resistance of the best modern stainless steels. It is not the easiest steel to grind or polish. S125V can beat it slightly in abrasive edge retention.

But within the group of stainless steels designed for exceptionally high wear resistance, S90V gives remarkably little away. It combines edge retention near the top of the scale with more toughness than S125V, S110V and ZDP-189 on the Knife Steel Nerds comparison, while remaining genuinely stainless.

That is a much more useful description than calling it a “super steel.” S90V is a specialized steel with a very specific strength: it preserves a cutting edge for a very long time without pushing the toughness tradeoff as far as some of the other extreme-wear stainless steels.

For a fine kitchen knife used as a cutting tool rather than an impact tool, that can be an excellent set of priorities. For another knife, a completely different steel may be better.

Sources, data quality and methodology

We deliberately separate manufacturer specifications, independent testing and our own interpretation. The numerical comparison charts are redrawn by Hikari Chef Knives from published Knife Steel Nerds rating data; they are not copies of Knife Steel Nerds graphics.

• Dr. Larrin Thomas, Knife Steel Nerds – Knife Steels Rated by a Metallurgist – common toughness and edge-retention rating scale.
• Knife Steel Nerds – S90V and S125V – dedicated toughness, CATRA, microstructure, hardness and heat-treatment work.
• Knife Steel Nerds – CPM S110V – S110V development and comparison with S90V.
• Knife Steel Nerds – ZDP-189 and Cowry-X – CATRA, carbide structure, sharpening and corrosion discussion.
• Knife Steel Nerds – VG10 and Super Gold 2 – same-hardness toughness comparison and SG2 edge-retention estimate.
• Knife Steel Nerds – CPM MagnaCut – toughness, CATRA, sharpening and geometry discussion.
• Knife Steel Nerds – Rex 45 / HAP40 testing.
• Niagara Specialty Metals – CPM S90V technical data sheet – composition, wear resistance, corrosion and processing information.
• Takefu Special Steel – SPG STRIX – manufacturer description, approximately 65 HRC, sharpening concept and corrosion testing.
• Takefu Special Steel – Super Gold 2 – manufacturer specification and hardness.

How to read this page: manufacturer claims are identified as such. Where independent data is missing, such as SPG STRIX edge retention and toughness, we say that it is missing rather than assigning an invented score. Where we make a metallurgical inference, we label it as an inference.

Last reviewed: August 2026.