Tribological Performance of Silver- and Oxygen-Doped Diamond-Like Carbon Coatings Under Nitrogen-Based Copolymer Additives

Abstract Additives made of nitrogen-functionalized copolymers were paired with diamond-like carbon (DLC) coatings doped with different amounts of oxygen and silver to form systems capable of improving tribological performance against undoped-DLC/additive systems. Initial characterisation indicated that silver doping reduced hardness and wettability in the surface, contrary to oxygen doping. Adhesion improved with higher doping levels. Tribological testing was done in boundary conditions, with silver-doped DLC coatings achieving a reduction in wear, but not friction. Oxygen-doped DLC coatings showed similar behaviour. Micrographs identified the wear mechanism as pure polishing and proved the protective effect of doped-DLC/additive systems. The findings suggest an across-scales effect of properties in the performance of the system and promising use in applications requiring wear resistance and friction reduction. Graphical abstract