Salt bath nitriding of 304 austenitic stainless steel at low temperature and corrosion resistance of nitriding layer

304 austenitic stainless steel was nitrided in a salt bath at low temperature(430 °C).The effects of nitriding time on microstructure,microhardness,and corrosion resistance of nitriding layer were studied.The phase composition,microhardness,cross-sectional morphology,and thickness of nitriding layer were examined by X-ray diffraction(XRD),microhardness tester,and optical microscopy.The results showed that the thickness and microhardness of nitriding layer on 304 stainless steel substrate are increased with the increasing of nitriding time.The layer obtained by nitriding for 1 h is composed of a single S phase.The 304 stainless steel shows improved corrosion resistance by nitriding and exhibits optimal corrosion resistance after nitriding for 4 h.