In our study, we investigated the wear, mechanical and tribological properties of plasma and pulse plasma nitrided AISI 4140 steel compared to hardened steel. Contact surfaces of the samples were fully characterized using metallographic, SEM microscopic, microhardness, and profilometric techniques, before and after wear testing. Wear tests were performed on a pin-on-disk wear testing machine in which nitrided pins were mated to hardened ball bearing steel disks under dry sliding conditions. Results show only slight improvement of the tribological properties of AISI 4140 steel after plasma and pulse plasma nitriding compared to hardening. However, improvements become more evident when testing conditions become more severe. It was also found that compound layer should be removed from the nitrided surface to avoid impairment of the tribological properties by fracture of hard and brittle compound layer followed by the formation of hard abrasive particles.
Surface properties of AISI 4140 steel modified by pulse plasma technique
