Achieving controllable friction of ultrafine-grained graphite HPG510 by tailoring the interfacial nanostructures

Abstract Graphite is an effective solid lubricant due to its self-lubricating properties. However, in practical environments such as ambient air and vacuum, the coefficient of friction (COF) of graphite is still high, resulting in serious wear that limits applications. In this study, two methods are proposed to improve the tribological properties of HPG510, including alcohol-processed two-dimensional (2D) nanomaterials as surface lubricating additives and deposition of a diamond-like carbon (DLC) film on the graphite surfaces. The results show that the COF of graphite decreases from 0.25 to 0.06 when lubricated by graphene oxide (GO)-processed alcohol solution. Similar performance is also observed for fluorinated graphene (GF), and tungsten disulfide (WS2) plus graphene (G) processed solutions. The identified mechanism is the combined lubrication effect of anhydrous alcohol and 2D lubricant materials. Meanwhile, the DLC-deposited graphite not only has a lower COF (∼0.10) but also possesses a significant enhancement of the wear resistance. An interesting finding about the anti-friction phenomenon is that some bulk DLC blocks are embedded in the lubricating tribolayer. The present work can provide reliable experimental evidence and a theoretical basis to expand the application field of bulk graphite.