Characterization of Cavitation-Erosion Resistance of Plasma Ion Nitrided 316L Stainless Steel Under Shock Wave in Seawater

: In this study, the characteristics of cavitation-erosion resistance of 316L stainless steel after plasma ion nitriding at various temperatures were investigated in natural seawater. Plasma ion nitriding was performed with N₂ and H₂ at a ratio of 1:4 from 400 to 500 °C for 10 hours. Micro-Vickers hardness measurement showed that the mechanical properties were improved by increasing hardness due to the formation of expanded austenite (S-phase) at 400 °C and 450 °C and γ'-Fe₄N and CrN phases at 500 °C. In the cavitation-erosion test, weight loss and damage rate decreased with increasing nitriding temperatures up to 450 °C, while the depth of damage was found to be increased at 500 °C. The lowest weight loss and damage depth were obtained at 450 °C, which measured the thickest layer of γN phase. At 500 °C, cavitation-erosion damage was significantly occurred due to the internal residual stress accumulated during the plasma ion nitriding.