Graphite nanoplatelets (GNPs) as an oil nano additive has gained importance to enhance the lubrication properties of renewable lubricants, such as vegetable oils. Using appropriately processed GNPs is necessary to gain the required tribological advantage. The present study investigated ball-milled GNPs, to understand the effect of GNPs concentration, and applied load on tribological behavior. Pin-on-disk tests were employed, to investigate the tribological performance of the nano-additive oil-based lubricant in the boundary lubrication regime. In order gain an understanding of the lubrication mechanism, Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and Raman Spectroscopy were performed for characterization. The study found that there is a critical concentration of GNPs, below and above which a reduced wear rate is not sustained. It is found that the tribological enhancements at the optimum concentration of GNP in boundary lubrication condition are a result of reduced direct metal-metal contact area at the interface. This phenomenon, along with the reduced shear strength of the ball-milled GNPs, is indicated to reduce the formation of asperity junctions at the interface and enhance tribological properties of the nano-additive oil-based lubricant.
Keywords: additives; ball milling; graphite nanoplatelet; lubrication; vegetable oil; wear.