Electrochemically deposited Ni+WC composite coatings obtained under constant and pulsating current regimes

Abstract

A series of Ni þ WC composite coatings were obtained by electrodeposition on a rotating disc electrode (RDE) from a commercially available Watts bath containing additives for brightness and smoothing and insoluble WC particles, using either constant or pulsating current. It was shown that the amount of WC embedded in the coating could vary from a few percent to over 80% depending on the rotation rate and the current density of deposition. Higher amounts (over 50 mass%) of embedded WC particles could be obtained only at rotation rates higher than 2000 rpm. It was also shown that the concentration of insoluble WC particles in the Watts bath has no significant influence on the amount of WC embedded in the coating, enabling the use of dilute mixtures (2 mass%ofWC in the solution). At higher amounts of embedded WC particles, rough deposits were obtained with the WC particles being mostly incorporated in agglomerates of different sizes (from about 50 lm to about 100 lm). It was also shown that under the same conditions of electrodeposition, higher amounts of embedded WC particles could be obtained from solutions containing smaller particles.