Electrodeposition and characterization of chromium-tungsten carbide composite coatings from a trivalent chromium bath

摘要

The electrodeposition of chromium from a trivalent chromium bath has been described in this work. The electrocomposite coatings of chromium with hard abrasive particles were investigated. The chromium- tungsten carbide (Cr-WC) composite coatings were obtained by suspending different concentrations of WC particles in a trivalent chromium plating solution to improve the various properties of the chromium deposit layers. The effect of operating conditions on the deposit layers has been studied. On the other hand, the effect of non-ionic polymeric surfactant [nonyl phenol ethoxylate with 12 units of ethylene oxide (NPE)] as an additive in enhancing the incorporation of the WC ceramic particles in the chromium metal matrix was investigated. It was found that the co-deposition of the WC ceramic particles depends on the concentration of the additive and its efficiency in reducing the surface tension of the electroplating solution. The mechanism of incorporation of WC particles into a growing deposit was suggested and discussed in view of the zeta potential and degree of wetability of WC particles in the plating solution. Furthermore, the adsorption behaviour of the additive on WC particles was analysed according to the Frumkin isotherm. The surface morphology and the distribution of WC in the chromium metal matrix were investigated. The properties of the deposit layers, hardness, corrosion resistance and wear resistance were determined and compared with free chromium deposits. The test results reveal that the Cr-WC deposit layer shows better performance compared with the chromium-free deposit. Copyright (c) 2005 John Wiley & Sons, Ltd.