Preparation and tribological properties of multi-layer graphene/silicon dioxide composites-based solid lubricant coatings at elevated temperatures

The solid lubricating coatings have an important role in hot metal forming. However, traditional lubricants can’t be applied to the harsh working conditions. In this investigation, the novel solid lubricant coatings including multi-layer graphene (MLG)/silicon dioxide (SiO2) composites and sodium metaphosphate phosphate were prepared. The high-temperature tribological properties of the solid lubricant coatings were investigated by friction and wear tester. The experimental results showed that SiO2 nanoparticles were evenly grafted by sol–gel method on the surface of MLG, forming MLG/SiO2 composites. MLG/SiO2 composites were presented excellent thermal stability at 800°C. In the range of 400–800°C, the average coefficient of frictions (COFs) were decreased from 0.3936 to 0.3663, and then increased from 0.3663 to 0.4226. Based on the analysis of wear scar, the lubrication mechanisms of the solid lubricating coatings were proposed. The low interlayer shear of MLG and the ball bearing of Si..., ,