The tribological performance in vacuum of DLC coating treated with graphene spraying top layer

Abstract

Reliable lubrication is the key to ensure the safe service of space equipment moving parts, but the tribological performance of most lubricating materials in a vacuum environment is substantially degraded. Therefore, graphene/diamond-like carbon (DLC) coatings were prepared on 9Cr18 bearing steel substrates using a combination of radio frequency (RF) magnetron sputtering preparation of DLC coatings and airbrush coating graphene layers, and the structural characteristics and tribological properties of the coatings were comparatively investigated for the different times of graphene layer spraying. The results shows that the graphene surface layer formed a stable bond with the DLC substrate, but there were local wrinkles in the graphene sheets deposited by the airbrush, and the surface roughness of the coating increased with the increase of the spraying times. The graphene/DLC coating with 3 times spraying has relatively excellent tribological properties in vacuum, with an average coefficient of friction of about 0.08 and a wear rate of 4.59 × 10−7 mm3N−1 m−1. Based on the tribological testing results, the mechanism of the friction-reduction and wear reduction of the graphene/DLC coatings in vacuum were analyzed. In general, the graphene/DLC coatings have excellent tribological properties in vacuum and hold significant promise for applications in moving parts of aerospace equipment.