Effects of Plasma Ion Nitriding Temperatures on Cavitation-Erosion Resistance of STS 304 in Seawater

Plasma ion nitridation was performed on stainless steel at various temperature parameters to characterize cavitation-erosion resistance under seawater conditions.Plasma ion nitriding was carried out at a relatively low temperature of 400 to 500 • C for 10 h at a gas ratio of 25% N2 + 75% H2 and a chamber pressure of 250 Pa in consideration of corrosion resistance by chlorine ions.Cavitation-erosion experiments were conducted for 10 h in compliance with modified ASTM G-32.The cavitation-erosion test for 10 h showed the lowest surface damage, weight loss, and depth of damage at 450 • C, where the γN phase was most deeply formed.On the other hand, at 500 • C, the cavitation-erosion damage tended to increase with increasing γ'-Fe4N phase and CrN.