5. Hot hardness testing

The need to know the properties of metals at the temperatures at which they are used led to the development of hot hardness testing. The higher the hardness, the longer the tool life.

On the one hand, we have established relationships between hardness and other mechanical properties, in particular tensile properties, measured at the same temperature, and on the other, we have linked the evolution of hardness as a function of time to the evolution of transient creep resistance at the same temperature. These relationships make it possible to determine the hot mechanical strength of alloys too brittle to be subjected to tensile tests (special steels, cutting carbides), or to rapidly obtain characteristics that take a long time to measure (evolution of strength with temperature, ageing, hardening, creep) (figure