Synergistic strengthening and tribological regulation in multi-phase 3D-printed PEEK composites

Polyetheretherketone (PEEK) suffers from a high coefficient of friction and substantial wear under demanding operating conditions, severely restricting its use in critical tribological components. To overcome these limitations, this study introduces a synergistic design strategy that enhances both the mechanical and tribological performance of PEEK by incorporating hybrid, multi-component fillers. PEEK composites reinforced with short carbon fibers (SCF), silicon nitride (Si₃N₄), and molybdenum disulfide (MoS₂) were fabricated via 3D printing and systematically evaluated. Mechanical testing revealed that the tensile strength of SCF/PEEK, SCF/Si₃N₄/PEEK, and SCF/Si₃N₄/MoS₂/PEEK composites increased by 27.2 %, 15.5 %, and 9.0 %, respectively, compared with pure PEEK. Correspondingly, hardness improved by 3.4 %, 5.6 %, and 9.5 %, confirming that the hybrid fillers effectively enhance load-bearing capacity. Tribological performance, assessed using a reciprocating friction and wear tester, showed a pronounced reduction in the coefficient of friction for the SCF/Si₃N₄/MoS₂/PEEK composite. Under loads of 50 N, 75 N, and 100 N, the friction coefficient decreased by 20.5 %, 42.9 %, and 50 %, respectively, relative to pure PEEK. At 100 N, the wear depth was reduced by 20.7 %, demonstrating superior wear resistance. Microscopic and energy-dispersive spectroscopy analyses revealed that SCF redistributes the applied load and promotes transfer film formation, Si₃N₄ particles mitigate matrix deformation and contact stress, and the layered MoS₂ structure enables interlayer slip, lowering shear resistance. The synergistic interplay among these reinforcements significantly improves both strength and tribological stability, positioning multi-phase 3D-printed PEEK composites as promising candidates for high-load, friction-sensitive applications.