Prominent wear resistance of a superlattice composite multilayered WC-enhanced a-C film under boundary lubrication conditions in aviation lubricant

To explore the applicability of a-C-based films in aviation bearings, a novel superlattice composite multilayered WC-enhanced a-C (CWCC) film and a traditional nanocomposite WC/a-C (WCC) film were prepared by an unbalanced magnetron sputtering system. The microstructures and mechanical properties of films were evaluated, and their friction behaviors under boundary lubrication conditions in aviation lubricant were intensively researched. In comparison to WCC film, the CWCC film showed significantly higher nanohardness and superior toughness attributing to its supperlattice multilayer structure and higher sp³ content. The EDS and Raman analyses indicate that there is only small amount of carbon on the wear scars against CWCC film, while evident tribofilms rich in phosphate and WO₃ formed on the wear scars against WCC film, leading to slightly lower friction coefficients of WCC film. However, CWCC film exhibits more superior wear resistance than WCC film. Especially, at 150 N and 200 N, the wear rate of CWCC film is only about 33.6% and 44.2% of that of WCC film, respectively. It was demonstrated that the novel CWCC film featuring excellent wear resistance in aviation lubricant possesses better potential for the application in aviation bearings.