The primary difference between Böhler M390 and M398 is their level of specialization: M390 is a highly versatile "super steel" with a perfect balance of toughness, corrosion resistance, and edge life, while M398 is an evolved variant optimized for extreme edge retention at the expense of toughness. Both are produced using third-generation powder metallurgy (PM) technology to ensure a fine, homogeneous microstructure.
Core Performance Comparison
Feature | Böhler M390 | Böhler M398 |
|---|---|---|
Typical Hardness | 60–62 HRC | 63–66 HRC |
Edge Retention | Very High | Exceptional (Top Tier) |
Toughness | Medium-High | Low (More brittle) |
Corrosion Resistance | Very High | Very High (Slightly lower than M390) |
Sharpening Ease | Difficult | Very Difficult |
Detailed Analysis
1. Composition and Wear Resistance
M398 is a direct modification of M390 designed to push wear resistance to its limit.
M390: Contains ~1.9% Carbon and ~4% Vanadium. It is one of the most popular steels for high-end folding knives because it stays sharp for a long time while remaining relatively stable.
M398: Significantly increases these elements to ~2.7% Carbon and ~7.2% Vanadium. This results in a much higher volume of hard vanadium carbides—30% carbide volume compared to M390's 20%—leading to superior abrasion resistance.
Testing Insights: Independent testing by Knife Steel Nerds has shown that M398 ranks near the very top of all stainless steels for edge retention, competing with S125V.
2. The Toughness Trade-off
The massive carbide volume in M398 makes the steel considerably more brittle.
Durability: While M390 can handle controlled impacts and tactical use reasonably well, M398 is prone to micro-chipping if pushed beyond simple slicing tasks.
Sharpening: Because it is so wear-resistant, M398 is a "nightmare" to sharpen without high-quality diamond or CBN abrasives from specialized retailers like Alpha Knife Supply.
3. Key Applications
Böhler M390: Ideal for Premium EDC Folders, custom knives, and high-end tactical tools where you want maximum cutting performance with enough toughness to handle daily utility tasks.
Böhler M398: Best suited for Slicing-Focused Tools, small high-performance cutters, and surgical or industrial instruments (like injection molding screws) where the tool must endure constant friction and abrasive wear.
Summary Verdict
Choose M390 for a reliable, world-class daily carry knife that balances all properties brilliantly.
Choose M398 if you are a "steel nerd" or professional seeking the absolute longest-lasting edge possible and are prepared for a very difficult sharpening process.