Effect of post-oxidizing temperature on tribological and corrosion behavior of plasma nitrided austenitic stainless steel

In this study, the effect of temperature of post-oxidation process on tribological and corrosion behavior of AISI 316 plasma nitrided stainless steel has been studied. Plasma nitriding was carried out at 450 °C for 5 h with gas mixture of N₂/H₂ = 1/3. The plasma nitrided samples were post-oxidized for 1 h with gas mixture of O₂/H₂ = 1/5 at different temperature of 400, 450 and 500 °C. The structural, tribological and corrosion properties were analyzed using XRD, SEM, microhardness testing, pin-on-disk tribotesting and electrochemical polarization. The results indicated that the nitride layer was composed of S-phase. The amount of S-phase decreased as the treatment temperature rose from 400 °C to 500 °C. In addition, it was found that oxidation treatment reduces wear resistance of plasma nitrided sample. It was demonstrated that the corrosion characteristics of the nitrided sample were further improved by post-oxidation treatment. The difference in corrosion resistance is mainly attributed to the thickness of the oxide top layer, which is governed by the post-oxidizing temperature.