Electrodeposition of nanocrystalline Ni/Ni–Al2O3 nanocomposite modulated multilayer coatings

Abstract

In this research, nanocrystalline Ni/Ni–Al2O3 nanocomposite modulated multilayer coatings were fabricated by direct current electrodeposition using dual bath technique. A Watts-type bath was used as the main solution of the baths. Saccharin was added to the first bath for producing nanocrystalline nickel layers and γ-alumina nanoparticles were added to the second bath to produce nanocomposite layers. The effect of coating's configuration like number of layers and their order was evaluated. The microstructures of the coatings, including relative texture coefficient and grain size, were studied by X-ray diffraction analysis. Energy dispersive spectroscopy and scanning electron microscopy were used to investigate the chemical composition and morphology of the coatings. Their tribological properties were investigated. The results exhibited that variation of order and configuration of layers had a significant effect not only on the adsorption of nanoparticles in the nanocomposite layers, but also on their growth texture in each multilayer coatings. In general, the results of tribological studies revealed that the optimum number of layers is 6 and all Ni–Al2O3/Ni CMM coatings, consisting soft layers (nanocomposite) and approximately hard layers (nanocrystalline), had better tribological properties than single layer nanocomposite coating and also worse performance than nanocrystalline one with the same total thickness.