Catalytic role of surface pre-treatment of noble-metal-like tungsten carbide powder on electroless deposition of nickel

In this paper, tungsten carbide (WC) powder without noble-metal activation pretreatment has been coated with a thick layer of nickel (Ni) particles by ultrasonic-assisted electroless plating process at room temperature. The surface morphologies and composition of original WC powder, pretreated WC powder, Ni-coated WC powder prepared in different electroless nickel plating (ENP) baths and worn WC-Ni composite powder were analyzed by field emission scanning electron microscopy (FE-SEM) and energy dispersion spectrometry (EDS). The results suggest that the initial WC powder, whether or not pretreatment, are both able to initiate ENP successfully. WC itself is considered to have noble-metal-like catalytic performance to induce ENP under the system of sodium hypophosphite as reducing agent. The surface defects created by specific chemical activation pretreatment not only effectively enhance the catalytic ability, but also improve binding force of WC substrate and Ni coating. Moreover, the composition of ENP bath is a key factor which can regulate the growth rate and adsorption rate of Ni particles to maximize the catalytic activity of WC powder.