Reinforcing fillers are of great importance in tribological performance and tribofilm formation of polymeric composites. In this study, the tribological properties of aramid particle (AP) and short carbon fiber (SCF) reinforced polyimide (PI) composites were added to hexagonal boron nitride (h-BN), and silica (SiO₂) nanoparticles sliding against alumina were comprehensively investigated. When sliding occurred with AP-reinforced PI composites, the tribological properties were not closely depended on the pressure × velocity (p × v) factors and the nanoparticles. The interactions between AP and its counterpart could not induce
tribo-sintering of the transferred wear debris. As such, the tribofilm seemed to be in a viscous state, leading to higher friction and wear. However, the inclusion of hard SCF into the PI matrix changed the interfacial interactions with alumina. A robust tribofilm consisting of a high fraction of silica was generated when the SCF-reinforced PI was added to the SiO₂ nanoparticles. It exhibited a high load-carrying capability and was easily sheared. This caused a significant decrease in the friction and wear of the PI composite at 8 MPa·1m/s. Moreover, due to their high melting point, few h-BN nanoparticles were observed in the tribofilm of the SCF-reinforced PI when hexagonal boron nitride was added.