Microstructure, mechanical, and corrosion resistance properties of Al0.8CrFeCoNiCux high-entropy alloy coatings on aluminum by laser cladding

Abstract

High-entropy alloys (HEAs) were used to improve the hardness, wear resistance, and corrosion resistance of steel surfaces by laser cladding due to their outstanding mechanical and corrosion resistance properties. However, there are only a few literary works on the improvement of wear resistance on the aluminum alloy surface by HEAs. In this work, the wear performance of laser cladded Al0.8CrFeNiCoAlCux HEA coating on aluminum alloy with different Cu contents was investigated in detail. Moreover, phase structure, microstructure, bonding shear strength, and corrosion resistance of HEA coatings were studied by XRD, SEM, tensile device, and electrochemical workstation. The result shows that with the increase of the Cu content, the structure of the coatings changed from BCC1 and BCC2 phases to BCC1, BCC2, and FCC1 phases. Evident cracks were observed in the Al0.8CrFeCoNi HEA coating. Meanwhile, when x = 0.25, the cracks disappeared, but the bonding shear strength was 79.6 MPa, only 34.7% of the substrate. At 0.5 ≤ x ≤ 1, the bonding shear strength of the Al0.8CrFeCoNiCux HEA coatings went above 175.2 MPa. As Cu promotes the formation of FCC phase, the hardness of the Al0.8CrFeCoNiCux HEA coating decreased as the Cu content increased. The effect of Cu on wear resistance has the same trend as with hardness. The wear rate of Al0.8CrFeCoNiCu0.5, Al0.8CrFeCoNiCu0.75, and Al0.8CrFeCoNiCu HEA alloys is only 3.4%, 4.02%, and 5.42%, respectively, of the substrate. The wear mechanisms of the substrate are that of delamination fracture and serious adhesion wear, while the wear mechanisms of Al0.8CrFeCoNiCux (0.5 ≤ x ≤ 1) HEA coatings are that of adhesive and abrasive wear. The corrosion resistance of Al0.8CrFeCoNiCux (0.5 ≤ x ≤ 1) HEA is better than that of the substrate in 1 mol l−1 H2SO4 solution. Al0.8CrFeCoNiCu0.5 has the best corrosion resistance that is characterized by pitting and intergranular corrosion.