CPM S90V

Overview

CPM S90V represents the pinnacle of edge retention in production stainless steels. Developed by Crucible Industries using their proprietary Crucible Particle Metallurgy (CPM) process, this powder metallurgy steel contains an exceptionally high volume of vanadium carbides—the hardest carbides commonly found in knife steels.

With 9% vanadium content, S90V produces microscopic, evenly distributed vanadium carbides throughout the steel matrix. These incredibly hard carbides (approximately 2800 on the Vickers hardness scale) give S90V unmatched wear resistance and edge retention among commonly available stainless steels.

Composition and Manufacturing

The chemical composition of CPM S90V includes:

• Carbon (2.3%): High carbon content for hardness and carbide formation
• Chromium (14%): Provides stainless properties and chromium carbides
• Vanadium (9%): Creates extremely hard vanadium carbides for wear resistance
• Molybdenum (1%): Enhances hardenability and toughness
• Manganese (0.4%) and Silicon (0.4%): Aid in deoxidation and processing

The CPM process uses gas atomization to create a fine powder, which is then consolidated under heat and pressure. This results in a much finer, more uniform carbide structure compared to conventional steelmaking methods, reducing the brittleness typically associated with high-carbide steels.

Performance Characteristics

Edge Retention

S90V’s edge retention is extraordinary. In CATRA testing—a standardized cutting test used by metallurgists—S90V consistently ranks as having the second-best edge retention among all tested stainless steels, narrowly trailing only the exotic S125V. In real-world use, properly heat-treated S90V can maintain a working edge through thousands of cuts that would dull conventional steels.

This makes S90V ideal for users who prioritize cutting performance and are willing to sharpen less frequently, even if sharpening takes more effort when needed.

Toughness

The trade-off for S90V’s exceptional wear resistance is reduced toughness. With approximately 10 ft-lbf in Charpy impact testing, S90V has moderate toughness for a high-carbide steel but is significantly less tough than steels like 3V or even S30V.

This means S90V is not recommended for:

• Heavy chopping or batoning
• Prying or twisting applications
• Knives subjected to lateral loads or impacts
• Hard use in cold environments

S90V excels at pure cutting tasks where the blade experiences primarily edge-on loads.

Corrosion Resistance

Despite 14% chromium content—well above the 10.5% minimum for stainless classification—S90V shows middle-of-the-road corrosion resistance. Testing reveals it performs adequately for most knife applications but falls short of ultra-corrosion-resistant steels like H1, LC200N, or even M390.

The reason: much of the chromium is tied up in carbides rather than being dissolved in the steel matrix where it provides corrosion protection. For most users in normal environments, S90V’s corrosion resistance is perfectly adequate, but it’s not the best choice for marine environments or harsh conditions.

Ease of Sharpening

S90V is genuinely difficult to sharpen. The high volume of extremely hard vanadium carbides creates significant challenges:

• Standard aluminum oxide stones will struggle and wear quickly
• Diamond or CBN abrasives are essentially required
• Sharpening takes more time and effort compared to conventional steels
• Maintaining proper angles is critical due to the effort involved

However, there’s a silver lining: vanadium carbides are harder than aluminum oxide but softer than diamond or CBN. This means that while sharpening is slow, it’s much easier than steels with even harder carbides, and the carbides won’t destroy your diamond stones the way some exotic steels can.

Heat Treatment Considerations

S90V requires expert heat treatment to achieve optimal performance. The steel is typically:

1. Heated to 2050-2150°F (1120-1175°C)
2. Quenched
3. Triple-tempered at 400-900°F (200-480°C) depending on desired hardness

Properly heat-treated S90V reaches 59-61 HRC while maintaining as much toughness as possible. Poor heat treatment can result in brittleness, reduced edge retention, or corrosion issues. When purchasing S90V knives, manufacturer reputation for heat treatment quality matters significantly.

Best Use Cases

CPM S90V shines in applications where:

• Edge retention is paramount: Users who make thousands of cuts between sharpenings
• Cutting cardboard, rope, or abrasive materials: Industries where blades see continuous cutting duty
• Premium EDC folders: Enthusiasts willing to invest in performance and maintenance
• Specialist applications: Where the blade will see pure cutting tasks without lateral stress

Practical Considerations

Pros:

• Industry-leading edge retention in a stainless steel
• Excellent wear resistance for extended cutting performance
• Adequate corrosion resistance for normal use
• Fine grain structure from CPM process reduces brittleness

Cons:

• Difficult to sharpen without diamond/CBN stones
• Lower toughness limits hard-use applications
• Premium pricing
• Requires expert heat treatment
• Not ideal for cold environments or impact loads

Conclusion

CPM S90V is a specialist steel that excels within its niche. It’s not a do-everything steel—the reduced toughness and sharpening difficulty make it unsuitable for many users. But for those who prioritize edge retention above all else and understand its limitations, S90V delivers unmatched performance in pure cutting tasks.

This is a steel for enthusiasts and professionals who make an informed choice about the trade-offs. If you need a blade that stays sharp through extended cutting sessions and you’re equipped with proper sharpening tools, S90V is among the best stainless options available.