Effect of Cu and Ni Inclusion on Tribological Performance of Tribocatalytically Active Coatings in Hydrocarbon Environments

Protective coatings are important for enhancing tribological behavior, preventing surface degradation, and reducing friction-induced energy losses during the operation of mechanical systems. Recently, tribocatalytically driven formation of protective carbon films at the contact interface has been demonstrated as a viable approach for repairing and extending the lifetime of protective coatings. Here, we study the effect of catalytic metals, specifically their composition and amount, on the tribocatalysis process. To achieve this, we test the tribological performance of electro-deposited amorphous CoNiP and CoCuP coatings in different hydrocarbon-rich environments. Our results indicate that the tribocatalytic repair of wear-induced damage is optimal when Ni and Cu are included in the Co-P matrix at 5 wt% Ni and 7 wt% Cu, respectively. Characterization of the wear tracks suggests that among the considered samples, the tribofilms formed on the surface of Co7CuP have the highest concentration of graphitic carbon, leading to a more significant reduction in the COF and wear rate. The carbon tribofilm formation was more pronounced in decane and synthetic oil than in ethanol, which is attributed to the difference in the length of the hydrocarbon molecules affecting viscosity and the lubricant film thickness during boundary lubrication sliding.