Synergy Between Corrosion and Wear of Electrodeposited Ni-W Coating

In this study, a block-on-ring wear tester was employed to investigate the tribocorrosion behavior of the electrodeposited Ni-W coating. Columnar grains embedded with lamellar and nanocrystalline microstructure were found in the fabricated Ni-W coating. The passivation of the Ni-W alloy was observed in the potentiodynamic polarization curve measured in 5 wt% NaCl solution. The result showed that with the raise of the applied overpotential, both the wear rate and the surface W-content of the coating increased. On the contrary, the accompanying coefficient of friction decreased with the potential. Small pitting and cracking occurred on the tested specimen. This microcracking structure was also observed in the corroded zone of the Ni-W coating by using TEM microscopy. A further XPS analysis determined the corrosion film was composed of Ni(OH)(2), NiO, and WO3 on the corroded surface. The formation of this porous corrosion film at high overpotential was found to cause an accelerated weight loss and thereby, the interaction between wear and corrosion, of the Ni-W coating under tribocorrosion.