https://doi.org/10.1038/s41598-025-14776-5
Poly(ether-ether-ketone) (PEEK) is a high-performance thermoplastic with excellent mechanical strength, thermal stability, and chemical resistance, making it attractive for applications like biomedical implants and prostheses. However, neat PEEK suffers from a high friction coefficient and pronounced wear in sliding contacts. In this work, composites of PEEK with Cobalt-Chromium (CoCr) alloy powder were fabricated by centrifugal powder compaction and vacuum sintering. Four composite compositions, with weight percentages of 10%, 20%, 30%, and 40% of CoCr, were produced. Scanning electron microscopy analysis confirmed uniform dispersion of CoCr particles within the PEEK matrix. Differential scanning calorimetry and thermogravimetric analysis showed that CoCr addition did not significantly alter PEEK’s melting temperature or thermal stability. Microhardness increased with filler loading, with the 40% CoCr composite achieving a 40% hardness improvement over neat PEEK. Ball-on-disk tests against steel revealed that all composites exhibited significantly reduced wear loss by 84% compared to neat PEEK, while maintaining a friction coefficient typical for PEEK-steel contacts. Overall, the PEEK/CoCr composites demonstrate enhanced hardness and wear resistance while retaining PEEK’s favorable thermal properties, suggesting their potential for applications requiring better tribological performance than unfilled PEEK.
Polymer-metal composites represent a significant advancement in materials science, offering unique combinations of properties that cannot be achieved by either constituent alone. Among high-performance thermoplastics, PEEK has garnered substantial attention due to its exceptional thermal stability, mechanical strength, and chemical resistance, which make it suitable for high-demand applications such as aerospace, automotive, and biomedical devices1,2,3. Particularly in orthopedics and dentistry, PEEK has gained popularity due to its favorable biocompatibility, radiolucency, and sterilization resistance2,4,5,6. Despite these advantages, neat PEEK demonstrates poor tribological behavior under dry sliding conditions, including a high coefficient of friction (COF) and substantial wear, limiting its service life in load-bearing or articulating components7,8,9,10.
To overcome these limitations, researchers have developed various PEEK-based composites by incorporating functional fillers aimed at improving frictional and wear behavior. These can be broadly categorized into solid lubricants, ceramic reinforcements, fiber reinforcements, and metallic fillers11,12,13,14,15,16,17. Among solid lubricants, polytetrafluoroethylene (PTFE), graphite, and molybdenum disulfide (MoS₂) have been widely used to reduce COF by forming transfer films during sliding9,15,18. For example, Burris et al.19 showed that PEEK/PTFE composites achieved ultralow wear rates (2 × 10⁻⁹ mm³/N·m) and a low COF (0.12). Similarly, carbon fiber/PTFE/graphite hybrid composites have achieved COF values below 0.2 against Co-Cr alloy surfaces20.
Ceramic fillers such as titanium dioxide (TiO₂), alumina (Al₂O₃), and silica (SiO₂) significantly improve hardness and wear resistance due to their intrinsic rigidity and load-bearing capabilities21,22. Titanium-based ceramic composites have been effectively used in biomedical crowns and load-bearing implants23. Fiber reinforcements, especially carbon and glass fibers, provide substantial improvements in strength and stiffness, although often at the cost of increased brittleness and anisotropy24,25,26.
Metallic fillers present a relatively underexplored but promising route to enhance both the mechanical and thermal properties of PEEK. Metals such as silicon, titanium, and aluminum offer improved dimensional stability, thermal conductivity, and surface hardness21,27. Oladele et al.28 provided a comprehensive review of polymer composites, emphasizing the potential of metallic fillers to improve mechanical strength and durability for structural applications. Goyal et al.29 demonstrated that the incorporation of aluminum nitride particles into PEEK significantly enhanced its thermomechanical properties, including glass transition temperature and modulus. Ochoa-Putman et al.30 emphasized the critical role of interfacial adhesion in determining the mechanical performance of polymer-metal composites, highlighting how chemical treatment of metal surfaces improves compatibility with polymer matrices. Furthermore, Dobrzańska-Danikiewicz et al.31 explored processing techniques for polymer-metal composites and noted that conventional methods often result in non-uniform dispersion of metal fillers, adversely affecting structural integrity. More specifically, Thiruchitrambalam et al.32reviewed the current state and future prospects of metal-reinforced PEEK composites, identifying processing challenges and potential applications. However, as observed by Siraj et al.7systematic investigations into the tribological properties of metal-reinforced PEEK composites remain limited. Notably, CoCr alloys are established biomaterials due to their wear resistance, corrosion resistance, and proven biocompatibility, making them ideal candidates for reinforcing polymers intended for medical applications33,34,35. Li et al.36 characterized the microstructure of biocompatible CoCr alloys, highlighting their potential for medical implants. Wu et al.37 investigated the properties of CoCr dental alloys fabricated via selective laser melting, demonstrating superior mechanical performance compared to conventional casting methods. In the context of composite materials, Senra et al.38 explored the potential of CoCr-reinforced polymers for biomedical applications, reporting enhanced bioactivity and mechanical properties. The superior wear resistance of CoCr alloys, as documented by Yan et al.39 suggests their potential as reinforcement materials for improving the tribological performance of polymers.
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