A tribocorrosion study of cobalt–tungsten electrodeposited coating with a mixed amorphous/nanocrystalline structure

Abstract

Cobalt–tungsten alloy coating with a mixed amorphous/nanocrystalline structure was electrodeposited from a citrate-ammonia bath. The coating showed a nodular surface morphology which had a microcrack network. During wear rubbing at OCP, the potential continuously increased to nobler values and then remained at high values even after the end of rubbing. Under anodic polarisation, rubbing caused a sharp increase in current density. However, at the end of rubbing, it returned to the initial value. The mass transport, depassivation, coating cracking and structure variation towards higher nanocrystalline content occurring at the wear scar played the major roles in determining the tribocorrosion behaviour of the coating. The formation of the superficial microcracks in the vicinity of the wear scars indicated a surface fatigue wear mechanism.