What is HAP40 steel? – [Complete Steel Guide]

HAP40 Steel

If you’re a real fan of Japanese Knives, I m sure you already heard of the HAP-40 Steel, they’re famous in the US Market for their extreme hardness and toughness. Therefore I decided to make a HAP-40 Steel Review.

So if you’re reading this article it means you wish to know more about the HAP-40, luckily I did some researches, and answered some common questions (like What is it? What is its chemical composition? What is its hardness? How hard is it? Is it good or no ? and other questions), So let’s dive in!

HAP-40 is a powder metallurgy High-Speed Tool Steel from @Hitachi Metals Ltd. It’s a mixture of high  Tungsten, molybdenum, Vanadium, and Cobalt, which makes it a very hard/tough steel, some knife expert consider it to be the best Japanese Steel.

HAP40 Steel Review

HAP40 steel composition

  • 1,27% of Carbon: It improves hardness and wear/corrosion resistance, but a high amount of it decreases strength.
  • 4,7% of Chromium: For tensile strength and Edge retention, and enhances corrosion resistance and wear resistance.
  • 5,4% of Molybdenum: Increase Machinability and strength.
  • 3,3% of Vanadium: Improves wear resistance and hardenability.
  • 8,5% Cobalt: boosts the individual effects of other components.
  • 6,5% Tungsten: Improves wear resistance and hardness.

As you can notice HAP40 Composition, is a Mixture of Chromium, Molybdenum, Tungsten, Cobalt, Vanadium and Carbon, which offers great hardness and great toughness.

Hap40 hardness (Rockwell Hardness)

Hap 40 has a Rockwell hardness of 64-68, the knives and blades made with Hap40 score a 65-66 HRC Hardness.

If you wish to know more about “Rockwell Hardness” or “HRC” Read this post.

HAP40 steel properties

According to the chemical composition and the HRC of the steel, the HAP 40 Steel has the following features:

HAP40 Edge Retention: with a maximum HRC of 68, the steel offers extremely good edge retention, might be the best edge retention you can find in high-carbon steel.

HAP40 Corrosion Resistance: Being a semi Stainless steel with only 4.7% of Chromium, which makes not the best for Corrosion Resistance.

HAP40 Wear Resistance: Great Wear resistance due to the Mixture of Chromium, Molybdenum, Tungsten, Cobalt, Vanadium and Carbon.

HAP40 Sharpness: The harder the Steel, the harder to sharpen it, HAP40 is hard steel so sharpen it wouldn’t be good.

HAP40 Toughness: Oh, boy! HAP40 Is tough steel, but it comes at the cost of corrosion resistance, you can’t have the tree altogether (Hardness, Toughness, Corrosion Resistance).

Will HAP40 Rust?

As mentioned above, it has low corrosion resistance. Therefore it needs to be taken care of (cleaned and oiled if it’s a knife).

Is HAP40 steel good for knives?

The answer of this question depends on the usage, but in general Yes, it’s great steel for knives, it offers great edge retention, great hardness, and great toughness, so if you intend to use in an extreme “beating or damaging way”, it would be great choice, but if you need to use it a wet or humid environment, it wouldn’t be the best, since it has a decent corrosion resistance, it doesn’t mean it will rust easily, but it will need more care than other high corrosion resistance steels.

HAP40 Steel Equivalent

The closest Steel to our HAP40 would be the CPM M4, they both have a mixture of high hardness, high toughness, high edge retention and decent corrosion resistance, they have a close chemical composition that includes Chromium, Molybdenum, Tungsten, Cobalt, Vanadium and Carbon.


In all the HAP40 is a great steel for knives, it’s a high-end steel knife that offers all that you can look for in a knife steel, And personally, despite its low corrosion resistance, I find it one of the best steels, the corrosion resistance isn’t a big problem (as long you take good care of your knife), So if you intend to buy/own/make a HAP40 Steel knife, I highly recommend it.

As always if you have another opinion about  HAP40, please leave it in the comments below, I’ll gladly discuss knives.

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