M390

Overview

M390 MICROCLEAN represents European powder metallurgy at its finest. Developed by Austrian steel giant Böhler-Uddeholm, M390 stands as one of the premier super steels in the knife industry, offering an exceptional combination of edge retention and corrosion resistance that few steels can match.

What distinguishes M390 is its remarkable 20% chromium content—among the highest of any knife steel—combined with the fine, uniform carbide structure that powder metallurgy provides. This gives M390 near-marine-level corrosion resistance while maintaining excellent wear properties. It’s a steel that delivers premium performance in harsh environments where both cutting ability and rust resistance matter.

M390 predates many American super steels, arriving before S90V, ZDP-189, or S30V. It established the template for what a high-performance stainless steel could achieve and remains a favorite among European knife manufacturers and discerning enthusiasts worldwide.

Composition and Manufacturing

The chemical composition of M390 includes:

Carbon (1.9%): Very high carbon content for hardness and carbide formation
Chromium (20%): Exceptional chromium content for outstanding corrosion resistance
Vanadium (4%): Creates hard vanadium carbides for wear resistance
Molybdenum (1%): Enhances hardenability and strength
Tungsten (0.6%): Contributes to wear resistance and hardness
Silicon (0.7%) and Manganese (0.3%): Aid in processing and deoxidation

The 20% chromium content is particularly noteworthy—it’s approximately 40% more chromium than S30V and significantly more than most knife steels. This high chromium level creates substantial chromium carbides (approximately 18% by volume) while still leaving enough chromium in solution to provide exceptional stainless properties.

Manufactured using powder metallurgy, M390 MICROCLEAN benefits from:

Fine, uniformly distributed carbides (both chromium and vanadium)
Absence of large carbide clusters that can act as failure points
Consistent performance across the material
Improved toughness compared to conventionally melted steels with similar chemistry

Böhler’s powder metallurgy process produces a fine-grained alloy with excellent dimensional stability and predictable heat treatment response, making it popular for precision applications beyond knives, including medical instruments and food processing equipment.

Performance Characteristics

Edge Retention

M390 delivers excellent edge retention that places it firmly in the premium tier. The steel contains approximately 2.5% vanadium carbides and 18% chromium carbides—a substantial total carbide volume that resists abrasion and wear exceptionally well.

In CATRA testing (a standardized cutting test), M390 consistently ranks in the top tier of commonly available steels. While it doesn’t quite match the extreme edge retention of S90V or S110V (which have 9%+ vanadium), M390 outperforms S30V, S35VN, and most conventional premium steels significantly.

Real-world performance:

EDC use: Maintains working edge for months with typical carry tasks
Professional applications: Chefs and tradespeople report excellent edge life
Demanding environments: Holds up to extended cutting of abrasive materials
Thin edges: The fine carbide structure supports very acute edge geometries

The balance of chromium and vanadium carbides gives M390 its character—it wears slowly and evenly, maintaining edge geometry rather than rounding over prematurely. This makes it particularly valuable for precision cutting tasks where edge profile stability matters.

Corrosion Resistance

This is where M390 truly shines. With 20% chromium content and significant chromium remaining in solution (not tied up in carbides), M390 offers corrosion resistance that approaches specialty marine steels like LC200N or H1.

In standardized salt spray testing, M390 scored exceptionally well—better than S30V, S35VN, S90V, SG2, and most other common knife steels. Only dedicated corrosion-resistant steels (H1, Vanax, LC200N) perform better, and those sacrifice significant edge retention to achieve it.

Practical implications:

Marine and coastal environments: Performs excellently with minimal maintenance
Food processing: Approved for food contact, resists acids and organic materials
Tropical and humid climates: Reliable without constant oiling
Neglect tolerance: Significantly more forgiving than lower-chromium steels

For users in harsh environments—whether that’s a fishing boat, a tropical jungle, or a professional kitchen—M390’s corrosion resistance is a major asset. It’s genuinely “stainless” in the practical sense, requiring far less maintenance than steels like D2 or even S30V.

Toughness

M390’s toughness is fair to good—adequate for most knife applications but not exceptional. Testing indicates approximately 10-15 ft-lbs in Charpy impact tests, which places it:

Better than ultra-high-carbide steels (S90V, S110V)
Comparable to or slightly below S30V
Significantly below dedicated tough steels (3V, CPM-CruWear, AEB-L)

The high total carbide volume (approximately 20%+) and high hardness (60-62 HRC) contribute to reduced toughness. In practical terms:

M390 handles well:

Normal EDC stresses
Typical folder applications
Controlled outdoor and bushcraft use
Professional cutting tasks

M390 is less ideal for:

Heavy chopping or batoning
Prying or twisting applications
Very thin edges in hard use (prone to microchipping)
Extreme cold environments
High-impact tasks

The powder metallurgy process does help—the fine, evenly distributed carbides mean M390 is tougher than a conventionally melted steel with similar chemistry would be. But it’s not a tough steel by design; it’s a wear-resistant, corrosion-resistant steel that maintains adequate toughness for appropriate applications.

Ease of Sharpening

M390 is difficult to sharpen—not as challenging as S90V or S110V, but significantly harder than conventional steels or even S30V. The high hardness (60-62 HRC typical) and substantial carbide volume create real challenges:

Standard aluminum oxide stones struggle and wear quickly
Conventional Arkansas stones require extreme patience
High-quality ceramic stones work but slowly
Diamond stones are highly recommended
CBN (Cubic Boron Nitride) abrasives are excellent

The good news: M390’s powder metallurgy structure means the carbides are fine and evenly distributed. This makes it somewhat easier to sharpen than you might expect from its hardness and carbide content. The steel responds predictably to proper sharpening technique, and the carbides won’t destroy diamond stones the way some ultra-exotic steels can.

Additionally, because M390 holds an edge so well, sharpening is infrequent. Many users find the trade-off acceptable—sharpen less often, invest more effort when you do. With the right tools (quality diamond stones or a good sharpening system), M390 sharpening becomes routine, if never exactly quick.

Heat Treatment Considerations

M390 is demanding regarding heat treatment and requires careful adherence to proper procedures:

Austenitize at 1950-2150°F (1065-1175°C) for 20-30 minutes in a controlled atmosphere (vacuum or nitrogen to prevent decarburization and oxidation)
Quench rapidly in oil or air
Cryo-treat in liquid nitrogen (-196°C/-320°F) to convert retained austenite
Double-temper at 350-500°F (175-260°C) for 2-4 hours

Target hardness for knives is typically 60-62 HRC, with the sweet spot at 61-63 HRC where the steel develops optimal properties—excellent edge retention while remaining relatively manageable to sharpen.

The heat treatment window isn’t particularly small, but mistakes can result in suboptimal performance. Poor heat treatment can lead to:

Hardness below 60 HRC (significantly reduced edge retention)
Inadequate cryo treatment (retained austenite leading to dimensional instability)
Improper tempering (brittleness or reduced hardness)

When purchasing M390 knives, manufacturer reputation is critical. Companies experienced with premium steels (Benchmade, Spyderco, Böker, We Knife Co.) typically deliver properly heat-treated M390. Budget manufacturers sometimes produce M390 at sub-60 HRC hardness values, which dramatically undermines the steel’s performance.

Historical Context and Market Position

M390 was developed as a powder metallurgy stainless tool steel for industrial applications requiring exceptional wear and corrosion resistance—specifically for applications like plastic injection molds, dies, and food processing equipment. Its adoption by the knife industry came as makers recognized its potential for premium blades.

M390 predates many American super steels, establishing itself before S90V, S30V, or most of Crucible’s CPM lineup became mainstream. This early introduction gave European manufacturers familiarity with high-performance powder metallurgy steel before their American counterparts.

The steel’s MICROCLEAN designation refers to Böhler’s powder metallurgy process, which produces exceptionally clean, uniform material. This branding emphasizes the steel’s premium positioning and manufacturing quality.

American Equivalents

M390 has two American near-equivalents:

CPM-20CV (Crucible Industries): Virtually identical chemistry and performance
CPM-204P (Crucible Industries): Very similar, optimized for certain manufacturing processes

These steels are so similar that performance differences are negligible in practice. The choice between them typically comes down to manufacturer preference and availability.

Common Applications

Premium European Knives

M390 is ubiquitous in high-end European folders:

Böker uses it extensively across premium lines
We Knife Co. features M390 in many models
Kizer Cutlery offers M390 options
Numerous European custom makers work with it
Price point: typically $150-$400+ knives

Tactical and Military Applications

The combination of edge retention and corrosion resistance makes M390 attractive for:

Military knives exposed to harsh environments
Maritime tactical applications
Specialized tools requiring minimal maintenance

Medical and Industrial Tools

M390’s food-contact approval and corrosion resistance make it suitable for:

Surgical instruments
Food processing blades
Laboratory cutting tools
Applications requiring sterilization

High-End EDC Folders

Enthusiasts seeking premium performance choose M390 for:

Daily carry in demanding environments
Professional use requiring reliability
Situations where frequent sharpening is impractical

Practical Considerations

Pros:

Excellent edge retention placing it in the premium tier
Outstanding corrosion resistance—among the best in knife steels
Approved for food contact
Fine-grained powder metallurgy structure
Proven track record in industrial and knife applications
Supports very acute edge geometries
Available from reputable manufacturers

Cons:

Difficult to sharpen without diamond or CBN abrasives
Fair toughness limits hard-use applications
Demanding heat treatment (quality varies by manufacturer)
Premium pricing (though reasonable for performance)
Can be prone to microchipping with very thin edges in hard use
High hardness can feel “brittle” to users accustomed to softer steels

Comparison Context

M390 occupies an interesting position in the steel hierarchy:

Compared to S30V:

Better edge retention
Dramatically better corrosion resistance
Similar or slightly lower toughness
Harder to sharpen
Generally higher cost

Compared to S90V:

Lower edge retention (S90V’s 9% vanadium wins)
Significantly better corrosion resistance
Better toughness
Easier to sharpen (though still difficult)
Better balanced for general use

Compared to Elmax:

Similar edge retention
Better corrosion resistance
Similar toughness
Similar sharpening difficulty
Different carbide structure (M390 has more chromium carbides)

Compared to newer steels (MagnaCut, Vanax):

Lower toughness (these newer steels prioritize toughness)
Comparable or lower edge retention
Similar or lower corrosion resistance (vs Vanax)
Similar sharpening difficulty

Conclusion

M390 represents the European approach to super steel design—prioritizing corrosion resistance alongside wear resistance, creating a steel that excels in harsh environments where both properties matter. It’s not the toughest steel, and it’s not the absolute edge retention champion, but it delivers an exceptional combination that few steels match.

For users who need a knife that can handle extended cutting tasks in wet, humid, or corrosive environments—whether that’s a fishing boat, a tropical deployment, a professional kitchen, or simply daily carry in a coastal city—M390 delivers premium performance with minimal maintenance requirements.

The steel’s approval for food contact, fine grain structure, and proven industrial heritage give it credibility beyond marketing hype. When a manufacturer chooses M390 and heat treats it properly, they’re choosing a steel with two decades of proven performance in demanding applications.

Is it perfect? No steel is. M390 won’t match S90V for pure edge retention, won’t match 3V for toughness, and won’t match modern steels like MagnaCut for overall balance. But for the specific combination of wear resistance and corrosion resistance, M390 remains among the very best options available.

If you’re looking at a knife in M390 from a reputable manufacturer, you’re looking at a steel that will deliver premium performance in challenging conditions. Just make sure you have diamond stones ready when it eventually needs sharpening.