Microstructural Analysis of 316LN Austenitic Stainless Steel by Salt Bath Nitriding Process

Austenitic stainless steel 316LN was subjected to salt bath nitriding at a temperature of 565°C for a period of 60, 80, 100 and 120 minutes. Influence of case depth based on nitriding time was investigated in the present study. Microstructural studies revealed an additional layer was developed on the surface with case depth varying from 7.1µm to 15.9µm. X-ray diffraction results confirm the formation of iron nitrides due to nitriding process. Growth of the nitrided layer is mainly because of nitrogen diffusion into the matrix in accordance with the parabolic rate law. Final study reveals that case depth of nitriding has a saturation limit and further increase in nitriding time doesn't yield any change in case depth. Vickers hardness measurements were used to study the influence of nitriding with varying the time.