Improving tribological properties of tool steels through combination of deep-cryogenic treatment and plasma nitriding

► Finer martensitic microstructure after deep-cryogenic treatment results in higher surface hardness and better tribological properties, especially galling resistance. ► Longer cryogenic treatment times give even finer microstructure and considerably improve galling properties. ► Increase in austenizing temperature leads to reduced volume fraction of carbides and consequently to increased friction and wear. ► Plasma nitriding improves tribological properties of P/M high-speed steel and reduces the effect of austenizing temperature. ► However, combination of nitriding and deep-cryogenic treatment might eliminate the beneficial effect of deep-cryogenic treatment.