The Effect of Laser Cladding Lap Ratio of TC4 Alloy on Microstructure and Properties of Ni60 Coating

Abstract

For improving wear resistance and hardness, Ni60 coatings were applied to TC4 alloy using laser cladding techniques. The effects of different lap ratios on the microstructure, microhardness, and wear resistance of the Ni60 coating were analyzed using an ultra-deep field microscope, XRD, microhardness tester and wear testing machine, and a suitable lap ratio was sought to obtain a coating with a better performance. The results showed that the Ni60 coatings with a 30% lap ratio had the best morphology and no obvious defects. From the bottom to the top, there are coarse columnar crystals, fine columnar crystals, equiaxed crystals, and acicular crystals, mainly composed of γ-Ni and some Cr7C3 and Cr23C6 phases. Therefore, the suitable lap ratio is 30%, and the microhardness of the coating at this parameter is 900 HV, which is about 2.5 times of the substrate (360 HV). The wear amount of the coating is 5.05 mg, which is about 11% of the substrate (44.23 mg). The average friction coefficient of the coating is about 0.41, which is 63% of the substrate (0.65). TC4 alloy’s wear resistance and microhardness can be significantly improved by applying suitable coating material and laser cladding parameters.