Study On SiC-316L Composite Coatings Of Magnesium Alloy Surface In Laser Alloying

At present, magnesium alloy has been widely used in many fields because of low density,high specific strength and rigidity, good thermal conductivity, as well as high-damping shockabsorption, strong electromagnetic shielding, easy cutting and recycling. However, the poorwearing and corrosion resistance seriously restrict magnesium alloy to fulfilling its potentialfor a long time. Therefore, it is great significant to use the surface modification treatment onmagnesium alloy.SiC-316L powder were prepared on the surface of AZ31magnesium alloy by lasersurface alloying with the powder preset in this paper. The phase, microstructure andcomposition of alloyed layer were analyzed by means of XRD, SEM and EDS. And hardness,wearing and corrosion resistance of alloyed layer were studied. The results show that theoverlap of alloyed layer is in good condition, and the surface is smooth, free of pilling,porosity and crack in certain range of laser process parameters. The weld pool depth ofalloyed layer is rising with the increase of laser power or decrease of scanning speed. Alloyedlayer consists mainly of Mg, Fe, SiC, MgO, and SiO₂. Columnar crystal zone whichperpendiculars to the interface and points to alloyed layer is formed in bondzone of weld poolbottom of alloyed layer and substrate.With the increase of laser power and scanning speed, microstructure of alloyed layer isobviously refined; but continuing to increase laser power, it becomes bulky and uneven. Withthe increase of spot diameter, microstructure becomes bulky. With the increase of laser power,the microhardness and wearing resistance of alloyed layer get the peak value; with theincrease of scanning speed, the microhardness and wearing resistance are on the rise; with theincrease of spot diameter, the microhardness and wearing resistance decrease.When the laser power is2200W, scanning speed is1200mm/min and spot diameter is2mm, the microstructure of alloyed layer is the most uniform, smallest and densest. Inaddition, the microhardness and wearing resistance are best. The processing parameters areoptimal combination. Compared with the magnesium alloy substrate, hardness and wearingresistance of alloyed layer are raised by two times and one time. The hardness of certain partsof alloyed layer’s surface, namely alloyed area on condition of this process is up to about600HV0.2.