Study On The Ni-nwc Nano-composite Coating By Electroplating

Nano- Ni-WC composite coating was prepared by means of electro-deposition in the nickel plating solution with nano-WC particles. The influence of cathode current density,pH value,temperature of solution,content of nano-WC,stir speed on the quality and properties of composite coating was studied. SEM and metalloscope were used to analyze the composition, structure and surface morphology of the composite coating.According to the contrastive research, the optimized plating solution composition was summarized as follows:NiSO4·6H2O 280-350g/L, NiCl2·6H2O 35-45g/L, H3BO3 30-40g/L, brightener 0.1-0.2 g/L, nano-WC 5-15 g/L, and appropriate surfactant and dispersant. And the optimized technique condition was as the following:cathode current density 2-4A/dm2, pH 4.0-4.8, plating temperature 45～55℃, stir speed 120-150r/min, plating duration 8 h, ultrasonic dispersing for 1 h before the plating. The composite coating prepared with the above condition has compact structure,high hardness and good binding with the substrate. But after long time electroplating, the nano-WC particles were reunited.According to the contrastive research on the micro-hardness,wear resistance,corrosion resistance of stainless steel,nickel-plate,nano-Ni-WC composite coating, the experiment results showed that the average micro-hardness of nano-Ni-WC composite coating (above HV 1006) is greatly higher than stainless steel (HV227) or nickel-plate (HV623), so the addition of nano-WC obviously increases the hardness of the coating, the strengthening effect of nano-WC does exist in the coating. In the same examine condition, the erosive abrasion of nano-WC- Ni composite coating is 1.4 times to stainless steel, but only 1.01 times to nickel-plate. The erosive abrasion of composite coating has higher increase than stainless steel, but only less increase than nickel-plate, reason is that the reunite of nano-WC particles weak the erosive abrasion improvement of the composite coating. In order to increase the wear resistance of composite coating greatly, we must avoid the reunite of nano-WC particles. The corrosion resistances of nano-Ni-WC composite coating and nickel-plate are much higher than stainless steel, but the corrosion resistance of nano-Ni-WC composite coating is a little lower than nickel-plate, so the addition of nano-WC can not improve the corrosion resistance of the coating obviously.