Steel Comparisons / M398 vs CPM S90V Knife Steel Comparison
For collectors and everyday knife users alike, high-performance steels are often the centerpiece of an excellent blade. Two steels that frequently come up in discussions about premium or “super steel” performance are Böhler-Uddeholm M398 and Crucible’s CPM-S90V. Both are powdered metallurgy steels celebrated for their exceptional edge retention, corrosion resistance, and high hardness. While they share several attributes, they also differ in important ways that can influence your decision for a particular knife or use case.
In this comprehensive guide, we’ll explore these two steels, dissecting their compositions, ideal hardness ranges, heat-treat details, and performance characteristics. By the end, you’ll have the knowledge to decide which steel—M398 or CPM-S90V—best suits your needs.
Böhler-Uddeholm M398 is a high-alloy stainless steel formulated to deliver outstanding wear resistance and impressive corrosion resistance. While exact numbers can vary slightly among sources or manufacturer batches, a generally referenced composition is:
This high carbon content, combined with substantial chromium and vanadium levels, gives M398 its excellent hardness and extended edge retention capabilities.
M398 is commonly hardened to around 60–64 HRC, with some makers pushing it toward the upper range to maximize wear resistance. As hardness goes up, toughness typically goes down, so knife makers must balance edge-holding with overall blade resilience to minimize chipping.
Crucible Particle Metallurgy (CPM) S90V is a pioneering super steel renowned for blending excellent edge retention with solid corrosion resistance. Its composition generally includes:
Large amounts of vanadium create extremely hard carbides, propelling CPM-S90V to the forefront of edge-holding capabilities.
CPM-S90V typically sits in the 59–61 HRC range, with certain custom treatments bringing it up to around 62 HRC. As with M398, higher hardness bolsters wear resistance but can increase brittleness, so most production knives aim for approximately 60–61 HRC for a good balance.
M398
CPM-S90V
Both steels are highly alloyed and require precise control at each stage of heat treatment to avoid warping or sub-optimal carbide formation.
Since both M398 and CPM-S90V contain high levels of chromium, they are classified as stainless steels and do not readily form a patina (unlike 1095 or W2 carbon steels). Most users will never see a patina on these steels under normal conditions. Protective coatings (e.g., DLC, PVD) are optional but may be applied to reduce reflectivity, improve blade aesthetics, or add an extra layer of wear protection.
Below is a quick-reference table that summarizes key attributes:
Attribute | M398 | CPM-S90V |
---|---|---|
Typical HRC Range | ~60–64 | ~59–61 (up to 62) |
Corrosion Resistance | Excellent | Very Good |
Toughness | Fair | Fair |
Edge Retention | Excellent | Excellent |
Ease of Sharpening | Poor | Poor |
Both steels stand out for top-tier edge retention, making them ideal for cutting tasks where the blade must remain sharp over extended usage. M398’s higher attainable hardness may offer an incremental boost in pure wear resistance, though the real-world difference from S90V is usually subtle for most users.
Neither steel is aimed at high-impact or prying tasks. They have “fair” toughness compared to more shock-absorbing steels. Used appropriately (for slicing, EDC, and kitchen work), both should perform without significant chipping.
In both steels, the high volume of vanadium carbides requires diamond or CBN abrasives for best results. Traditional sharpening stones (aluminum oxide, ceramic) tend to struggle, making the process time-consuming unless you have specialized equipment.
(Note: For those tackling their own sharpening, a slightly higher edge angle—around 20° per side—can offer a touch more durability for these ultra-hard steels, though some prefer more acute angles for push-cutting performance.)
While both come with a premium price tag, CPM-S90V is more commonly found in production models from major brands like Spyderco and Benchmade. M398 is still emerging and often appears in custom or limited-run knives. Expect higher prices and potentially longer waits to find an M398 blade.
Ideal Uses for M398
Reasons to Pick M398
Ideal Uses for CPM-S90V
Reasons to Pick CPM-S90V
Pros
Cons
Pros
Cons
Both M398 and CPM-S90V exemplify top-tier performance in the world of stainless, high-wear-resistant steels. Their fair toughness levels suffice for ordinary cutting and slicing but won’t excel in heavy-impact tasks or misuse scenarios.
• Choose M398 if you prize the highest possible edge retention at elevated hardness levels, coupled with excellent corrosion resistance—and you’re prepared for specialized sharpening methods. M398’s relative rarity also appeals to collectors seeking something exclusive.
• Choose CPM-S90V if you prefer a well-established steel that delivers nearly equivalent performance, is easier to source in production knife lines, and has ample user feedback confirming its reliability.
In either case, you’ll end up with a top-tier blade capable of exceptional sharpness and longevity. Both steels stand at the cutting edge of modern metallurgy, ensuring you’ll enjoy a knife that keeps performing longer than most competing alloys.
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