The Preparation And Properties Of Ni-SiC Composite Coating On AZ91D Magnesium Alloy

With the properties of light weight and high specific strength, the applications of magnesium alloy were highly concerned. The obtainment of magnesium with high corrosion resistance and wear resistance is the main issue of the magnesium study. In this paper, the C u2+ was added into the activation solution of magnesium alloy to improve the pretreatment process. In addition, the Ni-SiC composite coating was prepared by the Pulse Electroplating, and the process of Pulse Electroplating and the performance of the N i-SiC composite coatings were researched.First, the nickel was electroless-plated on the magnesium alloy as the pretreatment before electroplating. The result indicated that the electroplating nickel coating on the eletroless nickel coating presented a rough surface and there were chap veins on the coating surface However, the pre-copper coating deposited after the zinc-dipping was dense and smooth. After the plating of copper, the magnesium alloy was immersed into the Watt bath for the nickel plating. The nickel coating was successfully prepared on the AZ91 D magnesium alloy, which indicated that the pre-copper coating could protect the AZ91 D magnesium alloy from being corroded in the Watt bath well.The Ni-SiC composite coatings were prepared on magnesium alloy by Pulse Electroplating. It was found that the surface of the N i-SiC composite coating on AZ91 D magnesium was integrity, and the SiC paticles were distributed in the nickel matrix very uniformly. The wear resistance and corrosion resistance of the Ni-SiC composite coating both improved first and then decreased as the concentration of the SiC increased in the bath. When the dosage of SiC in the bath was 40 g/L, the corrosion resistance and wear resistance of the SiC composite coating achieved the best.With the duty cycle as the univariate variable, the influence of the duty cycle in the properties of the N i-SiC composite coating was studied. The result indicated that the N i-SiC composite coating prepared under the duty cycle of 50% possessed the best corrosion and wear resistance.