Study of the Nickel-Tungsten and Nickel-Cobalt Coatings Plated on Ductile Iron

Hard coatings such as nickel, chromium and tungsten can improve the surface properties of the substrate. The coating surfaces have been developed for increase of the wear resistance, hardness or corrosion resistance for industrial applications. Electroplating methods generally used to obtain producing these hard coatings and a novel brush plating process has the potential as an alternative of electroplating for industrial applications. In the present work, nickel-tungsten and nickel-cobalt alloys are coated on ductile iron by brush plating for surface characterization. Scanning electron microscopy and energy dispersive spectrometry were used to investigate the coating microstructures, surface morphology. The hardness of plating layers was measured. The results indicated that the nickel-tungsten coating was harder than nickel-cobalt coating. Excellent adhesion was obtained after nickel-cobalt plating. The tribological resistances were also significantly improved, as confirmed by the decrease friction coefficient and wear rate.