M398
Blade steels
M398 Steel
Description
M398 is a modification of Böhler’s M390, developed by increasing carbon and vanadium for extreme wear resistance. As a powder metallurgy stainless steel, M398 offers exceptional edge retention with very good corrosion resistance. However, toughness is among the lowest ever tested.
Composition (Böhler Data)
| Element | M390 | M398 | Change |
|---|---|---|---|
| Carbon (C) | 1.9 % | ~2.6 % | Increased |
| Chromium (Cr) | 20 % | ~20 % | Similar |
| Vanadium (V) | 4.0 % | ~7.2 % | Increased |
Properties
| Property | Value | Rating (1-10) |
|---|---|---|
| Hardness | 60–63 HRC | — |
| Toughness | Extremely low (among the lowest ever tested) | 2/10 |
| Corrosion Resistance | Very good (comparable to 20CV/M390, S110V) | 8/10 |
| Wear Resistance | Extremely high (25 % chromium carbide + 5 % vanadium carbide) | 10/10 |
| Edge Retention (CATRA) | Better than S90V, slightly below S125V | 10/10 |
| Sharpenability | Moderate (easier than S90V/S110V/S125V, harder than M390) | 4/10 |
Microstructure
M398 has a very high carbide volume: ~25 % chromium carbide and ~5 % vanadium carbide (compared to M390: 18 % chromium carbide + 2.5 % vanadium carbide). More carbide means higher wear resistance and edge retention, but reduced toughness. The carbides are coarser than other stainless steels in a similar property range.
Heat Treatment
| Step | Temperature / Duration |
|---|---|
| Austenitizing | 1170–1200 °C, 20 min |
| Quench | Plate quench |
| Cryo | Optional |
| Tempering | 180–220 °C (2× 2 hrs) |
| Achievable Hardness | 60–63 HRC |
Comparison with Related Steels
| Steel | Hardness | Toughness | Corrosion | Edge Retention |
|---|---|---|---|---|
| M398 | 60–63 HRC | 2/10 | 8/10 | 10/10 |
| M390 | 58–61 HRC | 4/10 | 9/10 | 9/10 |
| S90V | 59–61 HRC | 3/10 | 5/10 | 9/10 |
| S110V | 60–62 HRC | 3/10 | 8/10 | 9/10 |
| S125V | 61–63 HRC | 2/10 | 4/10 | 10/10 |
| ZDP-189 | 63–65 HRC | 3/10 | 6/10 | 10/10 |
Pros and Cons
Pros:
- Extremely high wear resistance and edge retention
- Very good corrosion resistance (comparable to M390/S110V)
- PM process delivers more uniform carbide distribution than conventional steels
Cons:
- Extremely low toughness (among the lowest ever tested)
- Coarse carbide structure for a PM steel
- Demanding to grind and sharpen
- Not suitable for high-stress applications
Conclusion
M398 offers very high edge retention for a stainless steel combined with very good corrosion resistance. However, toughness is extremely low, and the carbide structure is quite coarse for a PM steel. S90V and S110V offer better toughness with a similar level of edge retention. M398 is only suitable for special applications where maximum wear resistance is the priority and the blade is not subjected to high stress.