Al2O3 eliminating defects in the Al coating by laser cladding to improve corrosion and wear resistance of Mg alloy

Although Al produces a solid metallurgical bonding with Mg alloy substrates, micropores or crevices in the Al coating can reduce the resistance of Mg alloy to corrosion. In this study, a composite coating with a defect-free microstructure was prepared on the AZ31 Mg alloy substrate by introducing Al2O3 into the Al matrix via the method of laser cladding. On the one hand, Al2O3 with thermal insulation had a low thermal expansion coefficient and was not very prone to voids during laser melting. On the other hand, Al2O3 particles with a small size acted as the filler in the micropores or crevices. The Al/Al2O3 coating exhibited a smaller current density (2.1 x 10(-6) A/cm(2)) in comparison with those of bare substrate and Al coating (158.4 x 10(-6) and 3.1 x 10(-6) A/cm(2), respectively), which was mainly ascribed to the pore-free microstructure and high resistance to corrosion of Al2O3 phase. A favorable microhardness value of 95.3 HV was achieved for Al/Al2O3 coating, approximately 1.8 times higher than that of Al coating (52.8 V), which was mainly ascribed to the dispersion hardening of Al2O3 phase. Meanwhile, the Al/Al2O3 coating significantly reduced wear volume from 2.8 mm(3)/m of Al coating to 0.4 mm(3)/m, showing great potential for weight reduction applications.