Microhardness, wear resistance, and corrosion resistance of AlxCrFeCoNiCu high-entropy alloy coatings on aluminum by laser cladding

Abstract

To improve the surface properties of aluminum, AlxCrFeCoNiCu (x: molar ratio, x = 0, 0.1, 0.3, 0.5, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, or 2.0) high-entropy alloy (HEA) coatings were prepared via laser cladding. The microstructure, wear resistance, and corrosion resistance of the HEA coatings were studied. The structures of the AlxCrFeCoNiCu HEA coatings with Al addition changed from FCC1 to FCC1 + BCC1 and then BCC1 + BCC2 + FCC2 phases. Intercrystalline cracks were observed in the Al2.0CrFeCoNiCu coatings. The hardness of the AlxCrFeCoNiCu HEA coating was enhanced as x increased, where the hardness of the FeCoNiCrCu alloy (215HV0.2), which is the lowest among AlxCrFeCoNiCu HEA coatings, was higher than that of the substrate (79HV0.2). The effects of Al on wear resistance is similar to the hardness trend. The highest and lowest wear rates among the AlxCrFeCoNiCu HEA coatings were the FeCoNiCuCu (2.26 × 10−4 mm3/Nm) and Al1.5CrFeCoNiCu (6.6 × 10−7 mm3/Nm) HEA coatings, 67.4% and 0.19%, respectively, against the substrate. And the Al0.8CrFeCoNiCu coating shows good wear resistance, the wear rate is 1.9 × 10−5 mm3/Nm. The corrosion current density of AlxCrFeCoNiCu in 3.5% NaCl solution first decreased and then increased as x increased, but all were less than the substrate. Al0.8CrFeCoNiCu exhibited the best corrosion resistance, which was intergranular corrosion. The Al0.8CrFeCoNiCu HEA was found to be the most suitable for surface property improvements of aluminum alloys.