Friction and wear characteristics of synthetic diamond and graphene-filled polyether ether ketone composites

Modifying tribo films using filler particles is a significant area of research in developing polymer-based tribo components to minimize material loss during the sliding process. This study focused on altering the wear characteristics of a polyetheretherketone (PEEK)/graphene high-performance polymer composite to strengthen the tribo film by adding synthetic diamond particles. The hot-pressed PEEK composite reinforced by graphene and diamond particles increased the hardness and thermal stability of the composite. Compared with pure PEEK, composites containing 1% graphene and 1% diamond particles showed an increment of 25% and 23% in hardness and thermal stability, respectively. Fourier-transform infrared spectroscopy and X-ray diffraction analysis verified the compatibility and intactness of the fillers in the PEEK matrix. The tribo properties of PEEK composites were characterized by a pin-on-disc tribometer on a counter steel surface. A PEEK composite containing 0.75 wt% graphene and 0.5 wt% diamond particles exhibited the lowest friction of 0.17 at a pressure of 1.5 MPa. The specific wear rate was low (1.78 × 10⁻⁶ mm³/Nm) for the composite containing 1 wt% graphene and 1 wt% diamond particles at a pressure of 1.5 MPa. Varying synthetic diamond and graphene filler concentrations in the PEEK matrix change the wear process by modifying the tribo film characteristics, revealing the lowest friction and wear rate. X-ray photoelectron and Raman spectroscopy show that the polymer film was transferred to the steel countersurface, and the tribo-chemical products of the tribo film contribute to a stable tribo film. The ferric oxide film and the tribo film improve the composite’s self-lubricating properties and load-bearing ability. Hence, the composite containing 0.75% of graphene and 0.5% of a synthetic diamond can be employed in the sliding bearing application of continuous conveyors used in mass production systems.