Electrodeposition, microstructure and property of Co–WC composite coatings

Abstract

A novel Co–WC composite coating was fabricated on the surface of high-speed steel (HSS) substrate by direct current (DC) electrodeposition. The co-electrodeposition mechanism of Co–WC composite coating was explored. Furthermore, the effects of process parameters on the microstructure and micro-hardness of the coating were studied. The microstructure and composition of Co–WC composite coating were investigated by scanning electron microscopy equipped with an energy dispersive x-ray spectroscope. The adhesion strength of Co–WC composite coating was evaluated by WS-2005 automatic scratch tester. Results revealed that WC particles were homogeneously embedded in the Co matrix with few defects, and the Co–WC composite coating was firmly bonded to the HSS substrate. The optimized parameters are as follows: WC concentration of 35 g l−1, current density of 6.5 Adm−2, stirring rate of 300 rpm, and pH of 7.5 and temperature of 50 °C. X-ray diffraction analysis indicated that the Co matrix combined physically with the WC particles. Also, the microindentation hardness of Co–WC composite coating was tested by micro-hardness tester. It was found that the microindentation hardness of Co–WC composite coating reached the maximum value of 542 HV under the optimal process conditions.