Effect of nitriding time on the nitrided layer of AISI 304 austenitic stainless steel

The effect of plasma nitriding time on the microstructure and phase composition of nitrided layers on AISI 304 stainless steel was investigated. The phase composition and structure of the nitrided layer have been studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis of samples treated at 420 °C showed the presence of γN phase in the nitrided layers for all nitriding times involved in this study. The lattice parameters calculated based on γN(111) and γN(200) were different and became larger with time for up to 5 h of nitriding treatment. The surface hardness of nitrided layer was also increased with nitriding time. The maximum thickness of the nitrided layer reached 27 μm after 44 h of treatment in this study.