The Research on Technology of Electroless Ni-W-P Ternary Alloys Plating on the Aluminium Alloy

Abstract

To improve the surface hardness，corrosion resistance and wear resistance of the coating substrate, the ternary Ni-W-P alloy coatings were deposited on H12 aluminium alloy by electroless plating. The microstructure, phase transformation, plating velocity and hardness were investigated with X-ray diffraction technique, scanning electron microscope and differential thermal analysis. The results showed that when the PH value of electroless plating solution was 9.0 and the temperature of solution was 85°C, after 3h electroless plating, the substrate was completely covered by Ni-W-P plating, the surface was composed of uniform crystalline grains, their average diameter was about 7μm and they had no obvious defects, the contents of W reached up to 9.60%, and the hardness attained 610HV. In the temperature range of 75-90 °C, the plating rate has been increasing with temperature, when the temperature reached 90 °C, the plating rate reached as high as 13μm / h. When the temperature of heat treatment reached 336°Cfor 1h, the crystallization of Ni3P on the surface began to come into being. The maximum hardness of Ni-W-P plating was up to 920HV after heat treatment at 380 °Cfor 1h.