Tribological Behavior of Self-Lubricating PEEK/Graphite/Ti3SiC2 Composites Under Dry Sliding Friction

Most polymers and composites suffer from high friction and wear due to their inherent lack of self-lubrication under dry sliding friction. Herein, the lamellar Ti3SiC2 MAX material is prepared via vacuum sintering of a powder mixture containing Ti, Si, and TiC in the molar ratio of 1:1.1:1.8 at 1500 degrees C under a pressure of 30 MPa for 2 h. Combined with a soft graphite phase (5 wt%), self-lubricating PEEK/Graphite/Ti3SiC2 (PG-T) composites are successfully prepared, dependent on Ti3SiC2 (5 and 15 wt%) as a hard reinforced phase and lubrication additive. PG-T composites are fabricated via a multistep compounding approach using a twin-screw extruder. The incorporation of Ti3SiC2 and graphite within the PEEK matrix manifests a highly pronounced synergistic effect, which not only facilitates effective lubrication but also significantly enhances the load-bearing capability, thereby effectively circumventing direct contact between the counterface and the polymeric matrix. The sliding tests are conducted on the pins (diameter: 6.0 mm, height: 17.0 mm) and friction pair (45#steel, roughness Ra: 148 nm) under dry friction. In terms of PV-condition (up to 6 MPa and 3 m/s) (PV is a parameter that reflects the load-bearing capacity of polymer materials, which is defined by multi-plying the pressure P by the sliding speed V), PG5-T15 exhibits self-lubricating properties, featured by an average coefficient of friction (ACOF) as low as 0.119 for the pin-plate test and a specific wear rate (SWR) of only 0.58 x 10(-6) mm(3)/Nm. Meanwhile, PG-T composites present excellent thermal properties based on the thermal expansion coefficients (CTEs) and storage moduli (G ') during friction and wear. Considering the practical applications of tribo-composites, these findings highlight the potential of PG-T composite as a candidate for demanding tribological applications.