N690
Blade steels
N690 Steel
Description
N690 is a stainless tool steel from Böhler-Uddeholm with a composition similar to 440C, but with added cobalt (1.5 %) and increased molybdenum. The cobalt addition improves tempering resistance, making N690 suitable for coatings applied at high temperatures. Commonly used in pocket knives, kitchen knives, and diving knives.
Composition
| Element | Content |
|---|---|
| Carbon (C) | ~1.08 % |
| Chromium (Cr) | 17 % |
| Molybdenum (Mo) | 1.1 % |
| Cobalt (Co) | 1.5 % |
| Vanadium (V) | 0.2 % |
| Manganese (Mn) | 0.4 % |
Properties
| Property | Value | Rating (1-10) |
|---|---|---|
| Hardness | 58–62 HRC | — |
| Toughness | 5–7 ft-lbs at ~62 HRC | 5/10 |
| Corrosion Resistance | Good (Cr in solution ~12–13 %) | 7/10 |
| Edge Retention (CATRA TCC) | ~400–500 mm at 60 HRC | 5/10 |
| Carbide Volume | ~15–17 % (chromium carbides) | — |
| Tempering Resistance | Very good (due to cobalt) | 8/10 |
| Grindability | Good | 7/10 |
Microstructure
N690 shows a similar microstructure to 440C, mainly chromium carbides. The cobalt addition has little effect on the carbide structure but improves tempering resistance by suppressing martensite recovery.
Heat Treatment
| Step | Temperature / Duration |
|---|---|
| Austenitizing | 1050–1080 °C |
| Quench | Oil or air |
| Cryo | Optional (−80 °C to −196 °C) |
| Tempering | 150–200 °C (2×) |
| Achievable Hardness | 58–62 HRC |
Comparison with Related Steels
| Steel | Toughness | Edge Retention | Corrosion |
|---|---|---|---|
| N690 | 5/10 | 5/10 | 7/10 |
| VG10 | 5/10 | 5/10 | 7/10 |
| 440C | 5/10 | 5/10 | 7/10 |
| 12C27 | 7/10 | 4/10 | 8/10 |
| 14C28N | 8/10 | 5/10 | 8/10 |
Pros and Cons
Pros:
- Good corrosion resistance (comparable to 440C)
- Improved tempering resistance due to cobalt
- Good availability in Europe
- Easy heat treatment
- Suitable for PVD coatings
Cons:
- Moderate toughness (high carbide volume)
- Not a VG10 alternative (significantly different properties)
- Not PM-produced → coarser carbides
Conclusion
N690 is an alternative to 440C with improved tempering resistance due to the cobalt addition. The steel offers good corrosion resistance and moderate edge retention, but should not be seen as a direct alternative to VG10 due to significantly different properties. A solid choice for European knifemakers.