The capacity of an iron-carbon material to achieve a possibly high hardness which is assessed, for example, according to the penetration depth (hardness penetration capacity) or hardening capacity.

This is achieved by means of methods or combinations of methods where the components are heated to austenitization temperature 850°C) and then quenched in water, oil or air. The aim of this process is to transform the austenitic structure into martensite so that the material achieves an increased hardness and strength.

The martensitic transformation and the hardness achieved depend on a minimum cooling rate (critical cooling rate). Increased hardenability means easier martensite formation (obtaining a certain hardnesspenetration depth even with weaker quenching means) or an increase of the hardnesspenetration depth. In cast iron materials, this hardenability linked to the marteniste formation is also referred to as martensitic hardenability in contrast to the pearlitic hardenability.

Additional references:
Hardness test