Effect of post-oxidizing on tribological and corrosion behaviour of plasma nitrided AISI 5140 steel

A post-oxidation treatment was performed for times of 15, 30 and 60 min at a substrate temperature of 500 °C to investigate the tribological and corrosion properties of plasma nitrided AISI 5140 steel. The structural, mechanical, tribological and corrosion properties were analyzed by using XRD, SEM, microhardness testing, surface profilometry, pin-on-disk tribotesting and electrochemical polarization. The experimental results showed that oxide layer consists of magnetite (Fe3O4) and hematite (Fe2O3) phases. With increasing oxidation time, the thickness of the compound layer decreased due to the sputtering as a result of prolonged oxidation. In addition, it was found that the oxidation treatment after plasma nitriding provided an important improvement in the friction coefficient against a WC-Co ball, the wear rate and the corrosion resistance.