Microstructure and properties of the low-power-laser clad coatings on magnesium alloy with different amount of rare earth addition

Due to the low-melting-point and high evaporation rate of magnesium at elevated temperature, high power laser clad coating on magnesium always causes subsidence and deterioration in the surface. Low power laser can reduce the evaporation effect while brings problems such as decreased thickness, incomplete fusion and unsatisfied performance. Therefore, low power laser with selected parameters was used in our research work to obtain Al-Cu coatings with Y2O3 addition on AZ91D magnesium alloy. The addition of Y2O3 obviously increases thickness of the coating and improves the melting efficiency. Furthermore, the effect of Y2O3 addition on the microstructure of laser clad Al-Cu coatings was investigated by scanning electron microscopy. The energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD) were used to examine the elemental and phase compositions of the coatings. The properties were investigated by micro-hardness test, dry wear test and electrochemical corrosion. It was found that the addition of Y2O3 refined the microstructure. The micro-hardness, abrasion resistance and corrosion resistance of the coatings was greatly improved compared with the magnesium matrix, especially for the Al-Cu coating with Y2O3 addition.