An ultralow-wear silver-embedded diamond-like carbon films and the lubrication mechanism

Abstract

Currently, there is no consensus on the mechanistic role of silver (Ag) in governing the tribological behavior of diamond-like carbon (DLC) films, with particularly divergent findings regarding its wear resistance enhancement. This controversy fundamentally obstructs the elucidation of the lubrication mechanisms. Therefore, in this study, a series of Ag-embedded DLC (Ag-DLC) films with different Ag content were deposited by adjusting Ag target current, and the influence of Ag on the microstructure, mechanical, and tribological performances of DLC films was investigated systematically, emphasizing on the intrinsic lubrication mechanism. Results suggest that the incorporation of Ag with a suitable content plays a positive role in the tribological properties of DLC films, achieving ambient air lubrication performance comparable to oil lubrication conditions with a friction coefficient of 0.074 and ultra-low wear rate of 8.71 x 10-8 mm3 center dot N-1 center dot m-1. This is attributed to the higher degree of graphitization transformation and the formation of more unform transfer film at the frictional interface. Under oil lubrication conditions, as Ag target current increases, the friction coefficient decreases from 0.086 to 0.063, while the wear rates exhibit a oppose trend (negative effect), which is related to the degeneration of its mechanical properties. The related results provide a theoretical basis for optimizing the tribological performance of DLC films.