Effect of rGO concentration on the microstructure and friction behavior of co-doped diamond-like carbon (Ni/N/rGO-DLC) films

A kind of wear-resistant and lubricated Ni/N/rGO-DLC films are deposited on the surface of Ti-6Al-4V(TC4) alloy substrate by an integrative method involving pulsed electrodeposition and liquid-phase electrodeposition with various rGO (reduced graphene oxide) concentration. The growth mechanism of the film and the formation of protrusions and gully structures on the surface of the film are investigated. Furthermore, the mechanism of the effect of rGO concentration on the dispersion stability of the electrolytic system is explored. The results reveal that the Ni/N/rGO-DLC films at 0.07 g·L−1 rGO exhibit a uniform and dense structure. rGO particles are uniformly incorporated into the carbon-based films and tend to deposit perpendicular on the substrate. Simultaneously, the highest micro-indentation hardness, the lowest coefficient of friction and wear loss are obtained as 591.88 HV, 0.072 and 1.20 × 10−4 kg·m−1 of film with 0.07 g·L−1 rGO, which are principally attributed to the synergistic effect of rGO particles and amorphous carbon matrix in improving the mechanical properties of Ni/N/rGO-DLC films.