Enhanced wear property of magnesium alloy with Al+SiC coating by laser cladding

Al+SiC powders were pulse-laser (Nd-YAG) cladded on AZ91D magnesium alloy. The microstructure, chemical composition and phase analyses of the cladding layer were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, and X-ray diffraction (XRD) measurement. It can be seen that the composite coating is mainly composed of SiC and b-Mg17Al12 phases, and as well as metal phases of Mg and Al. The laser cladding showed very good bonding with the magnesium alloy substrate. It was found that with increasing SiC mass fraction, the spacing of the dendritic and cellular structure became larger. The surface hardness of cladding coating is higher than that of substrate, and the increase of SiC mass fraction can increase the surface hardness as the coating with 40% SiC particles shows a maximum hardness of about 180 HV, while that of 10% SiC particles is 136 HV. Sliding wear tests conducted in a pin-on-disc wear testing apparatus showed that the composite coating with SiC particles and in situ synthesized Mg17Al12 phase remarkably improved the wear resistance of the AZ91D magnesium alloy. The wear volume loss shows a decrease as the mass fraction of SiC increases from 10% to 30%, the coatings with about 20% to 30% SiC exhibit the best wear resistance.