Surface Characterization and Mechanical Properties’ Evaluation of Boride-Dispersed Nickel-Based Coatings Deposited on Copper Through Thermal Spray Routes

The present study concerns understanding the microstructures and wear resistance of nickel-based alloy (Ni 68.4, Cr 17, B 3.9, Si 4.9, and Fe 5.8) coatings on copper developed by flame spraying and high-velocity oxy-fuel (HVOF) coating techniques. The microstructure of flame spray deposition consists of predominantly equiaxed ??-Ni grains, refined Ni₃B precipitates, and Ni2.9Cr0.7Fe0.36 phase. On the other hand, HVOF spray deposition reduces the porosity content significantly in the presence of very fine (with average precipitate size varying from ??m to nm range) borides (chromium boride, Cr₂B; and nickel boride, Ni₃B) in ??-Ni matrix. The microhardness of the HVOF-sprayed and flame-sprayed surfaces were improved to 935?VHN and 251?VHN, respectively as compared with 82?VHN of the as-received substrate. Wear resistance property against WC indenter was also improved in deposited layers with a maximum improvement in HVOF spray deposition. The mechanism of wear was investigated.