Laser cladding Al-Si/Al2O3-TiO2 composite coatings on AZ31B magnesium alloy

To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31B magnesium alloys with Al-Si/Al2O3 -TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mg17Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness (50HV(0.05)) of the AZ31B substrate, that of the composite coatings (230HV(0.05)) is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCl solution.