Graphene based composite grease for elastohydrodynamic lubricated point contact

This paper present tribological and dynamic evaluation of reduced graphene oxide (rGO) sheets as an additive in lithium grease. Highly dispersion mixing method is used to mix rGO in commercial lithium grease to prepare composite grease. Tribological contact under investigation is established by ball-on-disc configuration. Friction, noise and vibration responses are recorded for the point contact lubricated with composite grease and base lithium grease in rolling and sliding-induced-rolling conditions. Relative speed of disc with the speed of ball is varied in order to get sliding-induced-rolling contact. Observations are performed at different nornal loads and fixed speed in elastohydrodynamic lubrication (EHL) regime. Results show existence of an optimum concentration (0.4% w/w) of rGO in commercial lithium grease. Friction, noise and vibration are recorded minimum for concentration of 0.4% w/w of rGO in commercial lithium grease. Reduction in friction coefficient is recorded up to 30% and 20% for rolling contact and sliding-induced-rolling contact respectively at optimum concentration of rGO in lithium grease. The lamellar structure of rGO in base grease controls the lubricity of concentrated point contact.