COMPARISON OF ELECTRODEPOSITION ASPECTS AND CHARACTERISTICS OFNi-WAND Co-WALLOYNANOCRYSTALLINE COATINGS

Abstract: current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism oftungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containingion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place viareduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot beruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition currentdensity. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. InCo-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared athigher current densities. In this system the grain size remained almost constant with increasing current density. Themicrohardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease intungsten content.Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different

کلیدواژه ها:

Co-W ، Ni-W ، electrodeposition ، EIS ، nanocrystalline ، coating