STUDIES ON EFFECT OF Nb SEGREGATION AND FORMATION OF SECONDARY PHASES OF Ni-Cr-Mo CLAD ON 316L SUBSTRATE BY COLD METAL ARC TRANSFER PROCESS

In current scenario, there is an ever increasing demand for alloys with increased wear resistance under severe working conditions. Ni-Cr-Mo alloy is suitable for surface modification and repairing applications. The Ni-Cr-Mo alloy clad region had cellular-dendrite with Laves phase and complex nitrides/carbides (MX) distributed in the interdendritic regions. Microindentation hardness variation was observed on the interdendritic regions as compared to that of dendritic regions. A new solidification path is confirmed through EDS analysis. Ni, Fe and Cr segregate to the dendritic area, whereas Nb and Mo segregate to the interdendritic region. Ni-Cr-Mo microstructure evolution was studied by optical microscope (OM), scanning electron microscope (SEM) and atomic force microscope (AFM). The Laves and G phases were identified in the Ni-Cr-Mo clad region, confirming superior resistance to corrosion. Pin-on-disc abrasion wear technique confirmed that cladding with low base metal dilution possesses better wear resistance. The mechanism of wear depends on load applied and sliding time. EBSD analysis revealed random texture and grains have same crystallographic orientation across the interface boundary line due to epitaxial growth.