Effect of nitrogen content on the cryogenic tribological behavior of austenitic stainless steel

Commonly used austenitic stainless steels (ASSs) have certain limitations in complex sliding wear conditions due to their relatively low yield strength and hardness. To improve the wear resistance, 316LN ASSs with different nitrogen contents (LNS: 0.14 wt%, HNS: 0.38 wt%) are prepared, to investigate the effect of nitrogen on dry sliding friction behavior and wear mechanisms at 0 °C, −60 °C, and −120 °C. Dry sliding wear tests are conducted using a ball-on-disk tribometer, with a GCr15 steel ball as the counterface. The results indicate that the wear rates of both LNS and HNS specimens decrease with decreasing temperature. At −60 °C, the LNS specimen exhibits better wear resistance than the harder HNS specimen, as martensitic transformation in the worn subsurface enhances its performance. However, at −120 °C, both LNS and HNS specimens undergo significant martensitic transformation, but the wear rate of the HNS specimen is lower due to its higher hardness, which significantly improves its wear resistance. Furthermore, the worn surface of the LNS specimen shows severe grooves, debris, and delamination, indicating abrasive and fatigue wear mechanisms. In contrast, the HNS specimen exhibits a relatively smooth worn surface with only mild abrasive wear. However, nitrogen-induced hardness enhancement in the HNS specimen leads to increased interfacial shear resistance during sliding, resulting in a higher CoF (0.5417) than that of the LNS specimen (0.5087).