Tribological properties of polyimide-graphene composite coatings at elevated temperatures

This paper focuses on developing a polyamic acid (PAA) of polyimide (PI) and PI filled with graphene (PI/GP) on 100CR6 ESU hardened steel. The tribological testing result of the pure PI and PI/GP against 100Cr6 steel ball at room temperature (RT) and elevated temperatures (50 degrees C, 100 degrees C, 150 degrees C, 200 degrees C) exhibits that the addition of GP clearly enhances the friction reduction and wear-resistant properties of PI, due to the excellent lubricating properties of GP. The 3 wt % of GP content in the PI is the optimum loading for the lowest friction and wear at RT and elevated temperatures. The SEM analysis of the worn surfaces showed that the high wear-resistant of the PI/GP composite is due to the generation of the loose particles from the coating surfaces which could be embedded on the friction pairs and rolled over there as a lubrication film. Also, at 60 % weight residue the PI/3GP showed the high decomposition temperature.