Comparative study on the morphology and tribological behaviour of Co/WS ₂ , Co/WC, and hybrid Co/WC–WS ₂ composite coatings

Co/WS2 and Co/WC composite coatings were electrodeposited from sulfate-based baths containing 0.5–10 g L−1 WS2 and 2–15 g L−1 WC particles. The influence of particle concentration on the structure, hardness, and tribological properties of the coatings was investigated. A hybrid Co/WC–WS2 coating was also synthesised to combine the high hardness of WC with the solid-lubricating properties of WS2. The morphology of cobalt changed from pyramidal to blade-like and finally to a porous structure consisting of rounded particulates with increasing WS2 content. Nodular and cauliflower-like morphologies were observed for Co/WC and Co/WC–WS2 coatings. Hardness decreased with the addition of WS2, from 330 HV for pure cobalt to 204 HV at 10 g L−1 WS2, whereas the addition of WC increased the hardness up to 530 HV at 10 g L−1 WC. The hybrid coating exhibited a hardness of 502 HV, reflecting a balance between WC strengthening and WS2 lubrication. Wear tests revealed that only the coatings prepared in baths containing 5 and 10 g L−1 WS2 particles exhibited lower wear resistance than pure cobalt. The hybrid coating delivered the best performance, with wear loss approximately 2.87 times lower than that of pure cobalt and approximately 1.25 and 1.37 times lower than those of the most wear-resistant 1 g L−1 WS2- and 10 g L−1 WC-reinforced coatings, respectively. Abrasion remained the dominant wear mechanism.