Solidified characteristic and enhanced properties of Al0.5MnFeNiCu0.5/Al–Ni functionally gradient coating fabricated by laser cladding on AZ91HP

To ensure the high entropy effect of the coating, it is necessary to control the dilution of Mg during laser cladding process. Therefore, Al 0.5 MnFeNiCu 0.5 /Al–Ni functionally gradient coating was proposed in this work. More remarkable, the design of Al–Ni transition layer effectively prevented the dilution of Mg into Al 0.5 MnFeNiCu 0.5 layer, and relieved physical and chemical differences between Al 0.5 MnFeNiCu 0.5 layer and Mg alloy. Al 0.5 MnFeNiCu 0.5 layer exhibited flower-like grain consisted of BCC phase. Al–Ni remelting layer crystallized as the fine snowflake-like grain. Al–Ni layer presented coarse needle-like grain morphology. Microhardness of Al 0.5 MnFeNiCu 0.5 layer was about 8.2 times more than that of the substrate. Specifically, compared with Mg alloy and Al–Ni layer, the wear volume of Al 0.5 MnFeNiCu 0.5 layer were decreased by 87.83% and 50.38%, respectively. The results of Polarization curve, Nyquist curve and Bode plot indicated that Al 0.5 MnFeNiCu 0.5 layer displayed better corrosion resistance than Al–Ni layer and Mg alloy.