Morphology and growth aspects of Cr(N) phases on gas nitridation of electroplated chromium on AISI 316 LN stainless steel

A gas-phase nitridation procedure has been investigated using a home-assembled TGA-MS system to enhance the high-temperature hardness and wear resistance of electroplated chromium on AISI 316 LN austenitic stainless steel. The sluggish diffusion kinetics of nitrogen in chromium and the presence of a thin oxide layer at the surface are the major constraints encountered during low-temperature gas nitridation process. This paper attempts to bring out a detailed correlation of the effect of nitridation environment, ammonia dissociation rate, substrate temperature and catalytic role of a thin nickel layer, on the nitriding characteristics towards addressing the above-mentioned limitations. XRD and SEM investigations on the nitrided specimens unambiguously reveal the morphology and the distribution of CrN and Cr2N phases formed during nitridation.