Why can't HRC be used for tungsten carbide products?

The measurement principle is inapplicable: HRC testing uses a diamond cone indenter with a 120° apex angle, pressed into the material surface under a certain pressure, and the hardness is calculated by measuring the indentation depth. Carbide has extremely high hardness and rigidity; the indentation produced by the diamond indenter under conventional HRC testing forces is very shallow, which may lead to inaccurate measurements or damage to the indenter.

The hardness range far exceeds HRC: The hardness of hardened tool steel is typically between HRC 58-65. However, the hardness of carbide, when converted to HRC, is generally above HRC 70, and can even reach HRC 80-90 (equivalent), which exceeds the effective and conventional comparison range of HRC measurement.