Microstructure and properties of W0.5Ta0.3MoNbVAlTi1-xZrx high entropy alloy coatings by laser cladding on the surface of 45# steel

Abstract

W0.5Ta0.3MoNbVAlTi1-xZrx (x = 0, 0.25, 0.5, 0.75, and 1.0) high entropy alloy coatings were prepared on the surface of 45# steel in this study using a laser cladding method. The resulting data demonstrate that increasing x changed the proportion of the phases but not the type of phases. Additionally, for all HEA coatings consisting of the BCC solid solution phase, Laves phase, MC phase, and unmelted W, the content of Laves phase was gradually decreased, and the HEA coatings microstructure was gradually transitioned from equiaxed to dendritic crystals. Solid solution strengthening, precipitation strengthening, and diffusion strengthening significantly increased the microhardness of the HEA coatings. The microhardness of the coating was the highest when x = 0.25, approximately 1.1–1.4 times that of other coatings. The wear mechanism of the HEA coatings was abrasive wear, and the wear rate first decreased and then increased with increaseing x. The combined resistance of the coating to micro-cutting and brittle debonding was the strongest when x = 0.5 with maximal wear resistance. The wear rate was only 43.8–82.9% that of other coatings. The increase in Zr content and decreasing Laves phase content reduced the number of defects and the formation of unstable oxides at the phase boundaries. The stability of the oxide layer was enhanced, and the coating exhibited the best high-temperature oxidation resistance when x = 0.75, approximately 1.4–6.3 times that of the other coatings.