Corrosion and tribological properties of nanocrystalline pulse electrodeposited Ni-W alloy coatings

Ni-W alloys with different tungsten content and grain size under 50nm were prepared by means of pulse current and pulse reverse current electrodeposition. The alloys were analysed using various methods (EDX, SEM and XRD). The electrochemical (open circuit potential, corrosion current density) and tribological (coefficient of friction and wear rate) characteristics were evaluated. Tungsten content in the alloys influences grain size which is responsible for the quality of the coating and the corrosion and tribological properties. When the content of tungsten in the Ni fcc lattice is lower than 5at.-% W, the corrosion resistance increases. When the content of W is higher than 5at.-%, the corrosion resistance decreases. The relationship between tribological properties and W content is the reverse of that experienced with corrosion properties.