Correlations between microstructure, nitrogen concentration and micro hardness of nitrided Ferritic Stainless Steel

Gas Nitriding of Ferritic Stainless steels AISI 430 was carried out at 600 , for various period of nitriding process which were for 2 hours, 8 hours and 24 hours. The effect of nitriding process period in term of microstructure, overall micro hardness, cross section hardness and nitrogen diffusion rate were investigated. The microstructures of samples were carried out using both Optical Microscope (OM) and Scanning Electron Microscope (SEM). The phase changes and Nitride precipitation formation were observed with respect to period of nitriding. Aside Microstructure, Energy Dispersive Spectroscopy (EDS) was conducted on the samples to investigate the nitrogen concentration inside the material. Vickers Hardness test have been carried out to investigate the effect of phase changes and it correlation toward the hardness of the materials.Unnitrided ferritic stainess steel having bigger size of grain boundaries were compared to nitride ferritic stainless steels and this is due to heat treatment during manufacturing process and concentration of nitrogen inside the steel.