CPM S90V vs M390 Knife Steel Comparison

CPM S90V vs. M390: Which Premium Knife Steel Is Right for You?

Below is a comprehensive comparison of two highly regarded powder metallurgy steels in the knife world: CPM S90V and M390. Whether you’re into bushcraft, EDC, or collecting high-end blades, these two steels often come up in discussions around premium performance. This post will guide you through their chemical compositions, typical heat-treat ranges, performance profiles (edge retention, toughness, corrosion resistance, and more), plus practical insights on sharpening, uses, maintenance, and cost considerations.

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1. Introduction to CPM S90V and M390

CPM S90V and M390 are both “super steels” produced using sophisticated powder metallurgy processes. Powder metallurgy helps ensure a more uniform distribution of carbides (critical in wear resistance and edge-holding) and delivers a refined grain structure. The result is a steel that can outperform many conventional alloys in a variety of blade applications.

• CPM S90V (produced by Crucible Industries) is well-known for its excellent edge retention and very good corrosion resistance. However, it can be fairly challenging to sharpen due to its high carbide volume, particularly vanadium carbides, and its high hardness potential.
• M390 (produced by Böhler-Uddeholm) is also celebrated for its impressive edge retention and excellent corrosion resistance. Compared to CPM S90V, M390 is somewhat easier to sharpen and finds popularity in both kitchen and everyday carry blades.

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2. CPM S90V: Detailed Overview

2.1 Typical Chemical Composition

• Carbon (C): ~2.3% – Crucial for hardness and wear resistance; high carbon also increases sharpening difficulty.
• Chromium (Cr): ~14% – Contributes to corrosion resistance and forms chromium carbides.
• Molybdenum (Mo): ~1% – Improves hardenability and high-temperature strength.
• Vanadium (V): ~9% – Greatly enhances wear resistance by forming hard vanadium carbides.
• Cobalt (Co): ~1% (often noted in some datasheets) – Can aid in grain refinement and further increase hardness.

Note: Some published compositions omit cobalt, but many official sources list around 1% Co in CPM S90V.

2.2 Typical Rockwell Hardness (HRC) Range and Practical Implications

CPM S90V is often hardened to around 59–61 HRC in practical knife applications, though some makers push it up to 62 HRC. Harder Rockwell levels mean better edge retention but can reduce overall toughness if taken too high. At these typical values, S90V remains fair in toughness but excels in maintaining a razor-sharp edge.

2.3 Key Performance Characteristics

• Corrosion Resistance: Very good. S90V contains enough chromium to resist most forms of rust, making it suitable for humid, wet, or even marine environments (though it’s not completely rust-proof).
• Toughness: Fair. Powder metallurgy steels with large amounts of hard carbides can be more prone to chipping under extreme stress.
• Edge Retention: Excellent. One of the best performing steels on the market when it comes to holding an edge for extended periods.
• Ease of Sharpening: Poor. Its high carbide volume and high hardness make it time-consuming to sharpen using standard equipment—diamond or ceramic stones are recommended.

2.4 Detailed Alloy Element Effects

• Carbon: Increases hardness and wear resistance but makes the steel wear on sharpening stones more slowly.
• Chromium: Enhances corrosion resistance and can form chromium carbides.
• Molybdenum: Improves the steel’s strength at high temperatures and helps in the hardening process.
• Vanadium: Creates extremely hard vanadium carbides, a major driver of S90V’s exceptional edge retention.
• Cobalt: Contributes to higher hardness and grain refinement.

2.5 Heat-Treatment Nuances and Forging

• Heat Treatment Range: Typically hardened between 59 and 61 HRC. Achieving the optimal balance of toughness and hardness can be more sensitive with S90V than with simpler steels.
• Potential Warping or Cracking: Advanced stainless PM steels like S90V can show increased warping risk if heat-treated improperly, especially if not stress-relieved before final hardening.
• Normalizing Cycles: Knife makers handling S90V usually follow detailed protocols, including preheat stages and controlled soaks, to ensure even carbide distribution.

2.6 Patina Formation and Protective Coatings

Due to its ~14% chromium content, CPM S90V does not develop a patina in the same way that high-carbon non-stainless steels (like 1095 or W2) do. A patina is essentially a layer of oxidation that forms on tools with less chromium. Because S90V has very good corrosion resistance, a patina is unlikely to form. It typically does not require a protective coating to resist rust, although coatings can still be applied for tactical or aesthetic reasons.

2.7 Ideal Uses of CPM S90V

• EDC Folding Knives: Perfect for those who value long edge retention for daily tasks and don’t mind a more challenging sharpening process.
• High-End Collectible Blades: Knife enthusiasts often admire S90V for its top-notch performance and premium reputation.
• Outdoor & Hunting Knives: While the toughness is fair, it’s still sufficient for many hunting or camping tasks where you prize edge holding—just avoid heavy batoning on hardwood if possible.

Why Pick CPM S90V Over Other Options?

• If you need a near “set-it-and-forget-it” edge that can handle plenty of slicing with minimal maintenance, S90V is hard to beat.
• Its premium performance and exclusivity appeal to collectors and serious users who demand top-tier cutting performance.

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3. M390: Detailed Overview

3.1 Typical Chemical Composition

According to Böhler-Uddeholm’s typical data, M390 includes:

• Carbon (C): ~1.9% – For high hardness and wear resistance.
• Chromium (Cr): ~20% – Grants excellent corrosion resistance and forms strong carbides.
• Molybdenum (Mo): ~3.8–4% – Boosts hardenability and high-temperature strength (some sources previously cited ~1%, but official data indicates closer to 4%).
• Vanadium (V): ~4% – Significantly increases wear resistance.
• Tungsten (W): ~0.6% – Aids in wear resistance and helps fine-tune grain structure.
• Silicon (Si): ~0.7% – Enhances strength.
• Manganese (Mn): ~0.3% – Minor contribution to hardness and grain refinement.

3.2 Typical Rockwell Hardness (HRC) Range and Practical Implications

M390 blades are often hardened in the 59–61 HRC range, although some heat treaters target 60–62 HRC for enhanced wear resistance. Like S90V, it performs best when carefully heat treated to balance hardness and toughness.

3.3 Key Performance Characteristics

• Corrosion Resistance: Excellent. M390’s ~20% chromium and well-distributed carbides make it an exemplary stainless steel.
• Toughness: Fair. It generally holds up well for most tasks but it’s not meant for super heavy-duty impacts.
• Edge Retention: Very good. While slightly behind S90V in absolute retention, M390 remains a top-tier choice for long-lasting edges.
• Ease of Sharpening: Good. Considered easier to sharpen than S90V, although still more demanding than mid-tier steels (like VG-10 or 154CM).

3.4 Detailed Alloy Element Effects

• Carbon: Heightens hardness and abrasion resistance.
• Chromium: At ~20%, it significantly boosts corrosion resistance.
• Molybdenum & Tungsten: Enhance wear resistance and impart strength at high temperatures.
• Vanadium: Key to forming tough, wear-resistant vanadium carbides.

3.5 Heat-Treatment Nuances and Forging

• Heat Treatment Range: Similar to S90V, around 59–61 HRC (some push to 62).
• Potential Warping or Cracking: M390 is generally stable if done properly, but like any high-end stainless PM steel, it requires careful control of soak times and temperatures.
• Normalizing Cycles: Detailed preheating protocols help ensure uniform structure and reduce the risk of distortion.

3.6 Patina Formation and Protective Coatings

Thanks to its high chromium content (~20%), M390 does not develop a patina under normal conditions. A protective coating is usually not necessary for corrosion resistance; however, some users prefer coatings to reduce glare or for tactical reasons.

3.7 Ideal Uses of M390

• Kitchen Blades: Fantastic for high-end kitchen knives since it combines excellent corrosion resistance with long edge life.
• EDC & Folding Knives: The steel’s combination of relative ease of sharpening and top performance makes it a favorite for EDC.
• General Outdoor Knives: M390 offers enough toughness for moderate outdoor tasks, plus excellent rust resistance for damp conditions.

Why Pick M390 Over Other Options?

• You want an outstanding blend of corrosion resistance, edge retention, and relative sharpenability.
• For consistent performance across different tasks, M390 is a true all-rounder at the top end of stainless steels.

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4. Side-by-Side Comparison Table

Below is a quick reference table summarizing their core attributes:

Feature	CPM S90V	M390
Corrosion Resistance	Very Good	Excellent
Toughness	Fair	Fair
Edge Retention	Excellent	Very Good
Ease of Sharpening	Poor	Good
Common HRC Range	59–61 (sometimes 62)	59–61 (sometimes 62)

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5. Real-World Performance and Applications

• Bushcraft & Survival: Both steels have fair toughness but excel more at slicing and edge retention than heavy prying or batoning. If your bushcraft style involves frequent carving or feather-sticking, either steel will hold a keen edge for a long time. However, if you frequently pound through hardwood or bone, you might prefer a tougher steel like CPM 3V.
• EDC (Everyday Carry): Either steel will serve you admirably for daily tasks: opening boxes, cutting rope, food prep, etc. S90V will hold its edge slightly longer, but M390 will be more forgiving to sharpen.
• Kitchen Use: M390’s excellent corrosion resistance and easier sharpening make it the more popular choice for high-end kitchen knives. CPM S90V can work well too but requires more diligence in sharpening.
• Tactical/Survival: For extreme tasks, both are slightly more prone to chipping than specialized tough steels. Still, they remain strong choices if your primary need is a very sharp, corrosion-resistant edge.

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6. Cost, Availability, and Maintenance

• Cost: Both steels demand premium prices. S90V can sometimes be slightly more expensive or less commonly stocked by custom knife makers. M390’s expanding popularity has made it somewhat easier to find.
• Availability: M390 is widespread in production knives (e.g., Benchmade, Zero Tolerance, and others). S90V is also found in many high-tier blades, but it may be slightly rarer.
• Maintenance: Given their strong corrosion resistance, routine wiping and occasional lubrication are typically enough. Just note that when sharpening S90V, you’ll need high-quality diamond or ceramic stones due to its abrasion resistance. M390 can be sharpened on similarly hard abrasives, just slightly faster.

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7. Pros and Cons Summary

CPM S90V Pros

• Outstanding edge retention—among the best in the market
• Very good corrosion resistance
• A premium choice for collectors and high-performance EDC

CPM S90V Cons

• Difficult to sharpen due to very hard carbides
• Fair toughness—may chip under heavy impact

M390 Pros

• Excellent corrosion resistance
• Very good edge retention with relatively good sharpenability
• Widely available in the knife market

M390 Cons

• Still a premium-grade steel; cost is higher than many mid-tier steels
• Fair toughness—like S90V, you need to be cautious with lateral stresses

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8. Concluding Thoughts and Recommendations

• If you prioritize absolute edge retention and don’t mind investing time in sharpening (or paying for professional sharpening), CPM S90V is a top-tier steel that will maintain its edge through extensive cutting tasks.
• If you want a steel that still has excellent performance but is more manageable to sharpen, leans slightly more on corrosion resistance, and is relatively easier to find in production knives, M390 is an outstanding choice.
• For bushcraft/tactical: Expect both steels to handle standard cutting chores extremely well. However, avoid using them for prying or other tasks better suited for high-toughness steels.
• For EDC and Kitchen: M390 tends to shine due to its slightly better ease of maintenance and sharpening. S90V remains a great choice for EDC if you desire minimal edge upkeep.

Ultimately, the decision comes down to whether you value the extreme edge holding and exclusivity of S90V enough to balance its sharpening difficulty against the all-around excellence of M390. By factoring in your typical use cases, sharpening skill, and budget, you can’t really go wrong with either steel—they’re both among the best in the business.

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9. Why Pick One Over the Other?

CPM S90V

• Best for users who want the pinnacle of edge retention in a stainless steel.
• Great for collectors who appreciate specialized steels and don’t mind a challenge in sharpening.

M390

• Exceptional choice for those who want top-level cutting performance that remains fairly user-friendly to maintain.
• Excellent for kitchen knives and EDC blades where corrosion resistance is paramount and the ability to resharpen more easily matters.

Whichever you choose, both steels represent the height of modern metallurgy for knife applications, showcasing how far performance steels have come. If you’re looking for a blade that offers reliability, high wear resistance, and superb corrosion protection, you’ll find a winner in either CPM S90V or M390.