D2
Blade steels
D2 Steel
Description
D2 is a high-alloy tool steel of the “High Carbon, High Chromium” category with about 12 % chromium and 1.5 % carbon. Developed around 1927, first used in knives by D.E. Henry in 1965/66. Offers good wear resistance and hardness with reasonable toughness. Also known as SKD11 (Japan), 1.2379 (Germany), K110 (Böhler), SLD (Hitachi), Sverker 21 (Uddeholm).
Composition
| Element | Content | Purpose |
|---|---|---|
| Carbon (C) | 1.50–1.60 % | Hardness, wear resistance |
| Chromium (Cr) | 11.0–13.0 % | Hardenability, wear resistance |
| Molybdenum (Mo) | 0.7–1.2 % | Air hardening, secondary hardening |
| Vanadium (V) | 0.15–0.45 % | Grain refinement, toughness |
| Manganese (Mn) | 0.15–0.45 % | Hardenability |
| Silicon (Si) | 0.10–0.60 % | Deoxidation |
Properties
| Property | Value | Rating (1-10) |
|---|---|---|
| Hardness | 58–62 HRC (up to 64 possible) | — |
| Toughness | Comparable to CPM-10V | 4/10 |
| Corrosion Resistance | Moderate (Cr in solution ~6–7 %) | 5/10 |
| Wear Resistance | Better than 440C, 154CM, N690 | 7/10 |
| Edge Retention (CATRA) | ~100 % (reference) | 6/10 |
| Grindability | Moderate | 5/10 |
Microstructure
D2 contains large chromium carbides that limit toughness and edge stability. Powder metallurgy versions (CPM-D2, since ~2007) and sprayform versions (PSF27, since ~2002) significantly reduce carbide size and improve toughness and corrosion resistance.
Heat Treatment
| Step | Temperature / Duration |
|---|---|
| Austenitizing | 1010–1080 °C |
| Quench | Air or oil (air hardening) |
| Tempering | 175–230 °C (2× 2 hrs) |
| Cryo | Optional for maximum hardness |
| Achievable Hardness | 58–62 HRC (up to 64 HRC possible) |
Notes:
- D2 is air hardening; oil provides faster cooling
- Always temper at least 2×
- Low tempering (150–230 °C): better toughness
- High tempering (480–565 °C): secondary hardening, less retained austenite
Comparison with Related Steels
| Steel | Wear Resistance | Toughness | Corrosion | Hardness |
|---|---|---|---|---|
| D2 | Reference (100 %) | 4/10 | 5/10 | 58–62 HRC |
| 440C | Lower | 5/10 | 7/10 | 58–61 HRC |
| 154CM | Lower | 5/10 | 7/10 | 59–61 HRC |
| 3V | Similar | 8/10 | 5/10 | 58–62 HRC |
| CPM-D2 | Slightly better | 6/10 | 6/10 | 58–62 HRC |
| S35VN | Higher | 7/10 | 8/10 | 58–61 HRC |
| M390 | Much higher | 5/10 | 9/10 | 58–61 HRC |
Pros and Cons
Pros:
- Good wear resistance — better than many standard stainless steels
- High achievable hardness — up to 62–64 HRC
- Air hardening — easy heat treatment, low distortion
- Widely available and cost-effective
- Proven over decades
Cons:
- Not truly stainless — only “semi-stainless”, can rust
- Large carbides (conventional) — limit toughness and edge stability
- More difficult to grind than simpler steels
- PM steels offer better property combinations
Conclusion
D2 remains a relevant knife steel despite the availability of more modern PM steels. The combination of cost, availability, and proven properties makes it attractive for budget knives, work knives, and larger blades. For maximum corrosion resistance, toughness, or edge retention, modern PM steels are superior.