Determination of tribological properties of ion-nitrided AISI 5140 steel

AISI 5140 low-alloy steel is ion-nitrided under different process parameters, including time (1, 4, and 8 h), temperature (450, 500, and 550 °C), and various gas mixtures at a working pressure of 5 mbar. The ion-nitriding behaviors of AISI 5140 steel have been assessed by evaluating tribological properties, surface hardness, surface roughness, compound layer thickness, and case depth by using a pin-on-disk wear machine, microhardness tester, surface profilometer, and scanning electron microscopy (SEM). It is found that ion nitriding improves the wear rate, and the presence of a hard and brittle compound layer on the surface causes an increase in wear of specimen surface. It is finally observed that ion nitriding parameters have no dominant effect on the friction coefficient.