Tribological Performance of Graphene and PTFE Solid Lubricants for Polymer Coatings at Elevated Temperatures

Some tribological applications demand reliable operation over a wide range of temperatures and the absence of liquid lubrication. Under these circumstances, polymer composite coatings have been suggested as an alternative to liquid lubrication. This study investigates the tribological performance of an advanced high-bearing aromatic thermosetting polyester (ATSP) coating filled with well-known solid lubricants, namely polytetrafluoroethylene (PTFE) and graphene nanoplatelets (GNPs). Mechanical and thermo-mechanical properties of the coatings were measured using nanoindentation and dynamic mechanical analysis. The tribological performance was experimentally assessed using a flat pin-on-disk configuration from room temperature to 300 degrees C with dry sliding conditions. The results showed that the addition of GNPs and PTFE could significantly decrease the friction and improve the wear resistance of the composite coatings, compared to neat ATSP coating. Both composite coatings demonstrated enhanced tribological performance with the increase of temperature. However, at the most extreme condition of 300 degrees C, the GNPs outperformed the PTFE by reducing the friction and wear by 53% and 69%, respectively, compared to room temperature. Optical and scanning electron microscopy were employed to further examine the formation of transfer films and worn surfaces.