Tribological properties and injection molding of SCF-reinforced PEEK/PTFE composites for radial piston hydraulic motors

Polyetheretherketone (PEEK)-based composites, renowned for their high strength and wear resistance, are promising materials for addressing friction and wear issues in high-load conditions, particularly in the friction pairs of radial piston hydraulic motors. In this study, short carbon fiber (SCF)-reinforced PEEK/polytetrafluoroethylene (PTFE) composite specimens were prepared using twin-screw extrusion and injection molding techniques. The tribological properties were assessed via ring-on-disc testing at varying SCF filling ratios. The results show that SCF significantly reduces both the friction coefficient (CoF) and wear rate (Wr) of the composites. However, the matrix's ability to fix the SCF is limited. At a 15 wt% SCF filling ratio, the composite achieves the lowest average CoF of 0.023 and Wr of 0.331 × 10⁻⁸ cm³ N⁻¹ m⁻¹, indicating excellent tribological performance. Microscopic analysis reveals that wear primarily occurs through slight plowing and adhesive wear. A three-layer bearing bushing containing 15 wt% SCF-modified PEEK/PTFE was tested under low-speed, high-load operating conditions, demonstrating excellent lubrication and load-bearing capabilities, making it suitable for high-load applications.