Polyetheretherketone (PEEK) is a high-performance thermoplastic widely used in orthopaedic and biomedical applications due to its excellent mechanical properties, biocompatibility, and suitability for additive manufacturing. However, its relatively poor friction and wear resistance limits its use in long-term, load-bearing implants. This study investigates the effect of hexagonal boron nitride (hBN) and silicon nitride (Si3N4) reinforcements on the mechanical and tribological performance of 3D-printed PEEK composites fabricated via melt blending and fused filament fabrication (FFF). The composites exhibited uniform filler dispersion, good printability, and tensile properties comparable to neat PEEK, along with maintained thermal stability. Under impact loading, reinforced samples showed enhanced energy absorption and a transition from complete fracture to hinge-type incomplete fracture, indicating improved resistance to crack propagation. Tribological evaluation under simulated joint conditions revealed that hBN-reinforced PEEK reduced friction (∼20%) and wear (∼50%), whereas Si3N4-reinforced PEEK increased friction (∼40%) and caused noticeable damage to the cobalt–chromium (CoCr) counter surface. These findings highlight the potential of hBN as an effective reinforcement for improving the tribological performance of 3D-printed PEEK composites, while also revealing limitations associated with Si3N4.
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