Friction and Wear Behavior of Plasma Source Nitrided Austenitic Stainless Steel

AISI 316 austenitic stainless steel was modified by plasma source nitriding technique at 450℃ for 6 h. The friction and wear behavior of the stainless steel substrate and surface modified layer against Si₃N₄ ceramic ball friction pairs was investigated comparatively under different loads by dry friction and wear tests. The wear morphology was observed and the wear mechanism was analyzed. The results show that a high-nitrogen γ_N phase layer with single face-centered-cubic structure and thickness of 17 μm was prepared on the surface of the tested steel after plasma source nitriding. The atom fraction of nitrogen element of γ_N phase layer was 15%-20% and the highest micro-hardness was about 1 510 HV0.01. The friction coefficient of the γ_N phase layer was equivalent to or smaller than that of the substrate under the same load, the specific wear rate was reduced by one order magnitude and the wear resistance was improved. The main wear mechanism of the substrate was adhesive wear. The main wear mechanism of the γ_N phase layer was oxidative wear under relatively low loads (2-4 N) and abrasive wear under relatively high loads (6-8 N).