Effects of various gas mixtures on plasma nitriding behavior of AISI 5140 steel

AISI 5140 steel was plasma nitrided at various gas mixtures of nitrogen, hydrogen, and argon to investigate the actions of hydrogen and argon on plasma nitriding. The structural and mechanical properties of ion-nitrided AISI 5140 steel have been assessed by evaluating composition of phases, surface hardness, compound layer thickness, and case depth by using X-ray diffraction (XRD), microhardness tests, and scanning electron microscopy (SEM). It was found that the growth of compound layer can be controlled and the diffusion improved when the gas mixture includes H2 gas. Additionally, it was determined that the amount of Ar in dual gas mixture must be at 20% minimum to obtain distinctive surface hardness and compound layer thickness.