Effect of plasma nitrocarburizing temperature on the wear behavior of AISI 4140 steel

In this study, the wear behavior of plasma nitrocarburized AISI 4140 steel at different treatment temperatures was investigated. Plasma nitrocarburizing was carried out at 530 °C, 570 °C and 630 °C for 5 h in an atmosphere of 80 vol.% N2, 17 vol.% H2 and 3 vol.% CO2. The treated samples were characterized using XRD, SEM, roughness and microhardness techniques. The wear behavior of the treated samples was studied by pin-on-disk method. The results confirmed formation of ε and γ´ phases in compound layer in all treatment temperatures. The amount of ε phase increased as the treatment temperature rose from 530 °C to 570 °C and decreased at 630 °C. Nitrocarburizing at 570 °C demonstrated the highest surface hardness, highest wear resistance and lowest friction coefficient among all treatment conditions.