Thermal transport and tribological properties of nanogreases for metal-mechanic applications

This study investigates the effect of incorporating nanoparticles - TiO2, Al2O3, CuO, and multi-walled carbon nanotubes (MWNTs) - within greases Mobilgrease 28 and Uniflor 8623B on their thermal transport and tribological properties. Nanoparticle filler fractions, varying from 0.01 to 0.10 wt%, were homogeneously dispersed within selected greases. Two tribological tests were performed on a four-ball tribotester; ASTM D5183, and the ITeEPib Polish method for testing lubricants under scuffing conditions. Anti-wear properties resulted in up to 20% wear scar diameter (WSD) reduction using a very low filler fraction of 0.01 wt% TiO2. For the extreme pressure test, the increase on the load-carrying capacity was found to be ~19% with a filler fraction of 0.05 wt% CuO. A guarded hot-plate method-based apparatus was used in order to characterize thermal conductivity of nanogreases, showing an enhancement of ~28% in thermal conductivity with the addition of 0.10 wt% MWNTs. These results demonstrate the potential of nanoparticle additives for improving thermal properties of greases while decreasing friction and wear of mechanical components.