Two-step strategy for improving the tribological performance of Si3N4 ceramics: Controlled addition of SiC nanoparticles and graphene-based nanostructures

Abstract The tribological behaviour of silicon nitride (Si3N4) ceramics is investigated using a two-step strategy. A set of ceramic composites containing silicon carbide nanoparticles (SiCn) is developed and, subsequently, graphene-based fillers are added to the Si3N4/SiC composite with the best tribological performance. The friction coefficient and the wear rate of Si3N4 are reduced up to 22 % and 40 %, respectively, when a 10 vol.% of SiCn is incorporated into the ceramic matrix due to its improved mechanical response. Si3N4/SiC composites containing 11 vol.% of graphene nanoplatelets (GNPs) or reduced graphene oxide sheets (rGOs) are analysed under isooctane lubrication and dry testing. rGOs composite leads to an important decrease of the friction coefficient (50 %) under lubricated conditions, and an enhancement of the wear resistance (44 %) under dry sliding tests, as compared to the reference Si3N4/SiC. The best performance of rGOs composite is due to the nature of the lubricating tribofilm and its excellent toughness.