Electrodeposition of Novel Nano-Composite Coatings of Niw Containing SiC and CeO2 with Outstanding Tribological Properties and Corrosion Performance

Abstract

A special electrodeposition process utilizing a well-designed reversed pulse (RP) current waveform and specially formulated bath chemistry were used to produce nanostructured composite coating of nickel-tungsten (NiW) containing silicon carbide (SiC) and cerium oxide (CeO2). In this bath formulation, a specific type of propargyl derivative compound was used as a grain refiner due to its acetylene-type of bonding (i.e. -C≡C-H) at the end of its alkyl chain. This typical bond had a tendency to be adsorbed at high current density locations on the substrate being plated resulting in better control of nickel ion diffusion towards the cathode. Therefore, a uniform and defect-free deposit with mirror-finish surface was obtained. As well, this compound increased the nucleation sites for initiating of metal deposition on the surface of substrate resulting in the decrease in grain size of nickel. The resulting material demonstrated outstanding corrosion and tribological performances. It was found that the addition of SiC and CeO2 improved the corrosion performance of NiW. It was also found that the composite of NiW-SiC obtained by RP waveform, performed better in corrosion resistance compared to the same coatings deposited by DC waveform. The electrochemical corrosion tests including potentiodynamic polarization (PP) and cyclic potentiodynamic polarization (CPP) tests were used to evaluate the corrosion behaviors of the deposits. Following the PP tests, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) was used to investigate the various corrosion products on deposits. As well, tribological properties including hardness, and wear resistance of the deposits were investigated