Influences of Laser Powers on Microstructure and Properties of the Al-Si/Al+Al2O3 Coating on the AZ91D Magnesium Alloy

摘要

An Al-Si/Al+Al2O3 coating was prepared on an AZ91D Mg alloy substrate by laser cladding of the plasmasprayed coating. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phases and to study the morphology, respectively. The adhesion strength and the porosity ratio of the coating were measured by using a tensile testing machine and an optical microscope (OM), respectively. The microhardness was measured using a micro Vickers hardness tester. The results show that after laser cladding, the adhesion strength of the coating increased from 10.78 to 25.17 MPa. When the laser power was 1400W, the metastable -Al2O3 phase in the coating transformed completely into the stable -Al2O3 phase. Along with the increase of the laser power, the porosity ratio of the coating decreased. But when the laser power was over 1400W, the porosity ratio increased. The microhardness of the surface was the hardest which was improved from HV0.05125 to HV0.05221. The larger the power of the laser was, the harder the coating was. But when the power was 1600W, the microhardness increased slightly, even the microhardness of the inter decreased.