HAP40 steel
HAP40 is a powder metallurgy high-speed steel from Hitachi Metals. It rates 8/10 for edge retention, 4/10 for toughness and 2/10 for corrosion resistance, and is usually hardened to 64–67 HRC.
At a glance
- Type
- High-speed powder steels
- Hardness
- 64–67 HRC
- Maker
- Hitachi Metals (Proterial) (Japan)
- Process
- PM
- Price tier
- Premium
- Used by
- Sukenari, Yu Kurosaki, Takamura (HSPS Pro), Hatsukokoro, Kei Kobayashi
- Also called
- HAP-40, Hitachi HAP40
Composition
| Element | Weight % |
|---|---|
| Carbon (C) | 1.3 |
| Chromium (Cr) | 4 |
| Vanadium (V) | 3 |
| Molybdenum (Mo) | 5 |
| Tungsten (W) | 6 |
| Cobalt (Co) | 8 |
| Manganese (Mn) | 0.4 |
| Silicon (Si) | 0.4 |
Source: manufacturer datasheet. Nominal values; where a range is published, the midpoint is shown. Phosphorus and sulfur, where listed, are maximums.
What makes HAP40 behave the way it does
HAP40 contains 1.3% carbon, enough to reach typical knife hardness; 4% chromium, too little for stainless behaviour.
Its 3% vanadium forms vanadium carbides, among the hardest carbides in knife steels, which drive wear resistance and slow edge loss but also make the steel slower to sharpen; tungsten (6%) adds hard carbides and helps the steel keep its hardness; molybdenum (5%) improves hardenability; cobalt (8%) strengthens the matrix.
It is made by powder metallurgy: the alloy is atomised into fine powder and consolidated, which keeps the carbides small and evenly spread. That is what lets a highly alloyed steel stay tough enough for a knife blade.
Japanese equivalent of REX 45; usually stainless-clad in kitchen knives.
Equivalent and similar steels
- REX 45 class (similar class; compositions differ): CPM REX 45, HAP40
Knives in HAP40
| Knife | Brand | Blade | Weight | Lock | List price | Buy |
|---|---|---|---|---|---|---|
| Sukenari HAP40 Gyuto 240mm | Sukenari | 9.13" | 6.6 oz | — | — | Blade HQ |
| Hatsukokoro HAP40 Gyuto 210mm | Hatsukokoro | 8.39" | 5.4 oz | — | — | Blade HQ |
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How to sharpen HAP40
HAP40 is slow to sharpen (3/10). Its vanadium and tungsten carbides are harder than the aluminium oxide in conventional stones, so diamond or CBN plates cut it far more efficiently. Once sharp, it needs touch-ups less often.
Compare HAP40 with
FAQ
Is HAP40 a good knife steel?
HAP40 is strongest in edge retention (8/10) and weakest in corrosion resistance (2/10). Its average across the four ratings is 4.2/10, and it sits in the premium price tier.
Does HAP40 rust?
Yes. HAP40 rates 2/10 and will rust or patina without care; dry it after use and keep a thin coat of oil on it.
Is HAP40 hard to sharpen?
HAP40 is slow to sharpen (3/10). Its vanadium and tungsten carbides are harder than the aluminium oxide in conventional stones, so diamond or CBN plates cut it far more efficiently. Once sharp, it needs touch-ups less often.
What hardness is HAP40?
Knives in HAP40 are usually hardened to 64–67 HRC. Makers can run it outside that range; harder means better edge retention but lower toughness.