Influence of Glow-Discharge Nitrided Temperatures of Cast Stainless Steel for Cavitation-Erosion Enhancement in Seawater.

In this work, corrosion resistance and cavitation-erosion characteristics were investigated by applying plasma ion nitriding technique to cast stainless steels used as materials of high speed rotors under seawater environment. Plasma ion nitriding was performed for 10 h at various temperature parameters with 25% N₂ and 75% H₂ gas ratio. The cavitation-erosion experiment was carried out under vibration amplitude of 30 °C and sea water temperature of 25 °C according to modified ASTM G32-92. The yN phase that improves corrosion resistance and mechanical properties was formed at the all of experimnetal temperatures after plasma ion nitriding treatment. The crystallite size of phases was calculated through the XRD patterns according to Scherrer formula and obtained smallest nano size of yN phase at 450 °C. Cavitation-erosion resistance was enhanced up to 450 °C but was deteriorated at 500 °C.