Effect of sputtering pressure on the surface topography, structure, wettability and tribological performance of DLC films coated on rubber by magnetron sputtering

Diamond-like carbon (DLC) films were deposited on the nitrile butadiene rubber substrates by magnetron sputtering. The effects of the Ar sputtering pressure (SP) on the surface topography, structure, wettability and tribological performance of the DLC films were investigated. The DLC films' morphology as a function of SP was studied by atomic force microscopy, and their structural properties were investigated using Raman spectroscopy and FTIR. The Raman results revealed that a high SP contribute to forming sp3 bonds. The surface energy was calculated by the Owens-Wendt-Rabel-Kaelble method, and it peaked at a SP of 1.4 Pa. Tribological tests were performed using a ball-on-disc tribometry at a fixed load of 0.3 N under ambient conditions, which revealed that the tribological characteristics of DLC films can be tuned by varying the SP. The results showed that the DLC films prepared under 1.4 Pa SP exhibited enhanced triboperformance, based on a stable coefficient of friction lower than 0.25 during the whole test, which was very promising for practical tribological applications.