Studies on the preparation and properties of electroless Ni–W–P alloy coatings and its nano-MoS₂composite

Abstract

The electroless Ni–W–P ternary alloy and its MoS2 composite films were successfully obtained on low-carbon steel by the electroless plating technique. The sodium tungstate concentration in the bath was varied to obtain Ni–W–P deposits containing various W and P contents. Ni–W–P–MoS2 composite was obtained with a suitable concentration of sodium tungstate in the plating bath. These deposits were characterized via x-ray diffraction (XRD), scanning electron microscopy and energy dispersive XRD spectroscopy studies. The corrosion behavior was investigated via potentiodynamic polarization and electrochemical impedance spectroscopy studies in a 3.5 wt% NaCl solution. An increase in codeposition of the alloying metal tungsten changed the structure and morphology of the deposits and enhanced the corrosion resistance. Mechanical properties such as microhardness and friction coefficients were evaluated. Ni–W–P deposits with increasing amounts of tungsten metal were found to possess higher friction coefficients. The microhardness was greatly improved with increasing codeposition of tungsten metal in the alloy. The incorporation of MoS2 nanoparticles into Ni–W–P alloy coatings strongly influenced in reducing the corrosion and friction.