Preparation and characterization of nickel based nanocomposite coatings with enhanced mechanical and surface properties

Abstract

Ni-W alloy and Ni-W/diamond monolayer and multilayer composite coatings were prepared by electrodeposition from a Ni-W plating bath with diamond particles suspended into the bath. Ni-W/diamond composite coatings were also prepared with varying amounts of Cobalt sulphate additives. The morphology and the composition of the deposits was investigated by means of SEM and EDS, respectively. The effect of operating conditions and additives on the Ni-W coatings were analyzed. The effect of the plating parameters, composite particle size, multilayer deposits and cobalt additives on microstructure and mechanical properties of the Ni-W/diamond composite coatings was investigated. The electrodeposited Ni-W/diamond deposits reported a maximum hardness of 1207 ± 32 Hv whereas, the maximum hardness reported by the Ni-W alloy coatings was recorded to be less than 750 Hv which underlines the significant impact the diamond particles have on enhancing the hardness of the base Ni-W matrix. The addition of Cobalt sulphate in the plating bath in smaller quantities tends to enhance the hardness and wear resistance of the Ni-W/diamond composite coatings and this trend is reversed as the amount of cobalt sulphate in the plating bath is increased beyond 0.1 g/L.