High-temperature oxidation behavior and corrosion resistance of in-situ TiC and Mo reinforced AlCoCrFeNi-based high entropy alloy coatings by laser cladding

In-situ TiC particles and Mo-enhanced AlCoCrFeNiMox(TiC)2-x high entropy alloy (HEA) coatings (x = 0, 0.5, 1, 1.5, and 2) were prepared via laser cladding. The effects of changes in x on the phase, microstructure, microhardness, high-temperature oxidation resistance and corrosion resistance of the HEA coatings were investigated. The results showed that the main phase of the coatings was the BCC phase; moreover, the Mo-rich area gradually increased and the size and morphology of the TiC particles underwent a series of changes with the increase in x. In addition, the σ and NiCrCoMo phases appeared when x = 1.5 and 2, respectively. Mo promoted the formation of a protective oxide layer and improved the stability of the passivation film, whereas the second phase increased the defects of the coatings, which determined the difference in the high-temperature oxidation resistance and corrosion resistance of the coatings. With an increase in x, the high-temperature oxidation and corrosion resistances of the coatings first increased and then decreased. The coating exhibited the best high-temperature oxidation resistance and corrosion resistance when x = 1, and its high-temperature oxidation resistance and corrosion resistance were respectively 5–12 times and 15–83 times better than those of the other coatings.