Study On The Coating Properties Of Laser Cladding NiTi And NiCrTi Coating On Magnesium Alloy

Magnesium alloy is the lightest metal material in practical applications.Magnesium alloy has the advantages of high specific strength and high specific rigidity,good shock absorption and cutting performance,good electromagnetic shielding performance.It is widely used in aerospace,automobile industry and electronic communication fields.But its insufficient wear resistance and poor corrosion resistance limit its further application.In this paper,a laser cladding process is used to first prepare a intermediated layer on the surface of the magnesium alloy substrate,and then laser cladding high-performance nickel-based alloy and nickel-chromium-based alloy coatings on the surface of the intermediated layer.By using scanning electron microscope（SEM）,energy dispersive spectrometer（EDS）,X-ray diffractometer（XRD）and X-ray photoelectron spectrometer（XPS）characterize the interface morphology and the coating structure;By using X-ray stress tester,friction and wear tester,microhardness tester,electrochemical workstation characterize the performance of the coatings.The results show:1.Ni70Ti30 coating can be prepared on the magnesium alloy substrate with better Mg-Al and Al-NiTi interface morphologies compared with the NiTi coatings that with other ratios of Ni and Ti.2.Compared with the intermediated aluminum layer,Al-Si-Y₂O₃ can improve the fluidity of the molten pool,refine the grains,and reduce cracks and pores.The bonding interface morphology between the Al-Si-Y₂O₃1.5 intermediated layer and the magnesium-lithium alloy substrate is the best.3.The hardness of the NiTi coating prepared on the Mg-Li alloy substrate with the intermediated layer reaches about 650HV0.2,which is 8 times higher than that of the Mg-Li alloy substrate,the wear resistance is greatly improved,and the corrosion resistance is also significantly improved.4.The NiCrTi coatings with different Ti content prepared on the surface of the optimized intermediated Al-Si-Y₂O₃1.5 layer all show good interfacial structure and form a good metallurgical bond with the intermediated Al-Si-Y₂O₃1.5 layer.NiCrTi35 coating has the highest hardness value and the best wear resistance of the coating,which is better than NiTi coating;the corrosion resistance of NiCrTi35 coating in 3.5%Na Cl solution is not much different from that of NiTi coating.5.The residual stress in the NiTi coating is relatively the largest,and the residual stress in the NiCrTi35 coating is relatively the smallest.The NiCrTi35 coating has no tendency to crack with the high performance.