Characteristics of electrodeposited cobalt and titania nano-reinforced cobalt composite coatings

Nano-crystalline Co and Co/TiO2 nano-composite coatings were electrodeposited from cobalt sulfate based solutions. Effect of electrolyte pH and nano-particles concentrations on the deposition rate, microstructure, morphology and hardness of the coatings were investigated. Tribological behavior of pure Co and Co/TiO2 coatings was studied and the results were compared with the substrate (316L). The results indicated that, deposition rate and grain size were increased by increasing of pH, while microhardness was decreased. Preferred orientation was also changed from mostly [001] at low pH to [100] at high pH values. Nano-composite coating with 3.6 vol.% TiO2 particles, deposited in a bath containing 20 g L− 1 TiO2, had the highest hardness value and wear resistance as compared to the other samples. Volume loss of this coating was about 5 and 33 times lower than the nano-crystalline pure cobalt and 316L SS substrate, respectively. However, pure cobalt coating had the lowest friction coefficient between all samples.