Study Of Az31Magnesium Alloy Surface Laser Cladding

As “Green Engineering Materials in21st Century”, magnesium alloy is the new favor ofindustry for its excellent properties such as low density, high specific strength and stiffness,high damping, good machining property and strong electromagnetic shield, etc. But its poorperformance in hardness, corrosion resistance and wear resistance lead magnesium alloy islimited to widely apply in industry to some extent. In order to expand and explore themagnesium alloy’s apply potential, some proper surface modification methods must beadopted to improve its hardness, corrosion resistance and wear resistance, which has animportant impact on the wide application of magnesium alloy.In this paper, in order to improve the properties of corrosion resistance and wearresistance, AZ31magnesium alloy is treated with laser cladding technology, a316L coatingand a SiC-316L composite coating are conducted on AZ31magnesium alloy surfacerespectively. The316L coating and SiC-316L composite coating is studied by OM、SEM、EDS and wear tester from the following aspects: Microstructure, phase, wear properties andcorrosion resistance.The experiment of laser cladding316L coating on AZ31magnesium shows that, theoverlap of cladding layer is in good metallurgical bonding, the thickness of cladding layer isabout621um. EDS test shows the coating mainly consists of Mg, MgO, Fe and Mg17Al12composition. Hardness analysis result shows that the hardness of316L coating is about2.7times of AZ31magnesium substrate. Wear resistance is studied from grinding depth, wearloss and relative wear resistance, grinding depth is0.61um,50%lower than the substrate; thewear loss is about0.0858g, lower55.2%than that of original magnesium alloy; the value ofrelative wear resistance is2.23. The result of corrosion shows that the corrosion rate of316Lcoating is19.435.3g/m2h, while the corrosion rate of AZ31magnesium alloy is35.3g/m2h,which is about2time as long as316L coating.In order to obtain better performance, the SiC ceramic powder is mixture into316Lpowder with the mass ration1:10, then laser cladding on AZ31magnesium alloy withSiC-316L composite powder. The obtained cladding layer is about316um, which is composedof black irregular phase SiC, grey particle316L and white Mg substrate. EDS result shows thatthe cladding layer is composed of Mg、MgO、Fe、SiC and Mg17Al12. Hardness analysis resultshows that the hardness of SiC-316L composite coating is about5.4times of AZ31magnesium substrate. Wear test result shows that, SiC-316L composite coating possessesbetter performance than316L coating, its grinding depth is only0.56um, and wear mass lossis0.0425, lower77.8%than that of magnesium alloy, the value of relative wear resistance is 4.51. The corrosion rate of SiC-316L composite coating is3g/m2h, which is about1/11as lowas substrate, and1/7as low as316L coating.