The influence of pulse plating parameters on the hardness and wear resistance of nickel-alumina composite coatings

Pulse plating of nickel-alumina composite coatings was studied and the effects of pulse parameters, i.e. duty cycle and frequency on the hardness and wear resistance of these coatings were investigated. At the same average current density and other experimental conditions, low pulse frequencies (10-20 Hz) and duty cycles (10-20%) produced harder coatings. The hardness was decreased by increasing either the frequency or the duty cycle of the pulsating current used for deposition. In general, the nickel-alumina coatings deposited by pulse current were harder than the same coatings produced from the same bath with dc current. Similar to their hardness, utilization of pulse currents was found to increase the wear resistance of these coatings. Decreasing duty cycle and frequency increased their wear resistance in the same manner that pulse parameters influenced their hardness.