Effect of Nb on the microstructure and wear resistance of In625/(Nbx+SiC0.5) composite coatings by laser cladding

In this study, different amounts of Nb (0–8 wt%) were added into In625 powder mixtures to prepare In625/(Nbx + SiC0.5) composite coatings on In625 substrate by laser cladding. The effects of Nb content on the phase composition, microstructure, microhardness and wear resistance of the coatings has been comprehensively investigated. The results show that Nb can promote the precipitation of NbC, Cr23C6 and Laves in the coating while refining the grains, and carbides are not only enriched at grain boundaries to play the role of pinning, but also diffuse precipitation within the grain to play the role of diffusion strengthening. The formation of more laves phases in the coating is promoted by excessive Nb content, which ultimately leads to the uneven distribution of microstructure in the coating. When the Nb content reaches 4 wt%, the NbC with uniform distribution and good adhesion with the substrate can effectively reduce the fracture and detachment of the hard phase in the abrasion process, resulting in optimal wear resistance. While the wear resistance of the coating decreases instead when the Nb content is too high. Overall, the alloying effect of Nb changes the content and distribution of reinforcing phases in the coating of In625 matrix composites, enhancing the uniformity of microstructure, resulting in an increase in the hardness and wear resistance of the coating.