Nitrogen implantation of steels: A treatment which can initiate sustained oxidative wear

Falex wear tests on mild (SAE 3135) steel samples treated by either nitrogen implantation (2.5x1017 N2+ cm-2 at 180 keV) or low temperature (about 3150C) oxidation are reported. The results show that both treatments lead to about an order-of-magnitude reduction in the long-term wear rate of the steel. In addition to the wear rate measurements, the wear member asymmetry behavior, scanning electron microscopy studies, Auger spectra and sputter profiles all indicate that the wear modes induced by both treatments are the same and are oxidative wear. These results confirm the previously proposed initiator-sustainer wear model in which implanted nitrogen simply acts as an initiator of favorable oxidative wear but is not directly involved in maintaining the sustained wear resistance. Possible mechanisms for both the initiation process and the sustained wear process are reviewed and discussed. (orig.)