Class I, Type D, Ni-HiCr; Also known as Ni-Hard4

ASTM A532 Class I, Type D, Ni-HiCr (Ni-Hard 4)

Nickel-High Chrome cast iron with high chromium content is the solution of the low toughness of the Ni-Hard family under the impact condition. Unlike the other Ni-Hard alloys, Class D with M7C3 carbides is more fracture-friendly under the impact load. 

Specifications of the Ni-Hard 4 are significantly changed by heat treatment and can be  used in wide wear applications; from low wear and low impact to high wear and high impact.

Increasing the Cr content to minimum 7% and Si content to 2% makes the discrete carbides structure which  increases toughness.

These alloys have excellent fluidity and castability and are good for complex shape casting.

The volume fraction of carbides in the NiHard 4 is less than the other NiHards nevertheless, having the higher hardness 

carbides (M3C7) and their morphology make them tougher with comparable hardness.

Chemical Composition (ASTM A532-1D)

Mechanical and Physical Properties

Wear and Abrasion Resistant Properties


Ni-Hard 4 alloys are suitable for high impact, sliding abrasion for both wet and dry applications. ASTM A532 Class 1 Type D has the highest toughness and wear resistance among the other Ni-Hard alloys. They are therefore used for more severe applications that justify the added alloy cost. Typical applications of this group are in pump volutes handling abrasive slurry, coal pulverizing table segment and wheels.


Ni-Hard 4 is produced in as-cast, Stress Relieved (SR) and heat-treated condition.

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