A comparative bio-tribological study of self-mated PEEK and its composites under bovine serum lubrication

In this study, the bio-tribological performances of polyether-ether-ketone (PEEK) 450G and its composites (carbon fiber reinforced PEEK-CA30, carbon fiber/graphene/polytetrafluoroethylene reinforced PEEK-FC30, and glass fiber reinforced PEEK-GL30) were systematically investigated under self-mating combination. During 2 million cycle tribo-tests, PEEK bearings all exhibited two-stage wear. The total mass losses were 9.03 ± 1.87, 9.59 ± 0.22, 11.29 ± 1.30 and 23.01 ± 0.77 mg for 450G, CA30, FC30 and GL30, respectively. It was obvious that, glass fiber reinforcement was not favorable and had the highest wear loss among the four PEEK bearings (P ≤ 0.001). In respect to PEEK 450G, CA30 was superior in wear performance, with a 62% of reduction in steady state wear factor. While FC30 was comparable to that of 450G. Plowing grooves, scale-like wear scars, and wear debris attachment were observed within the wear zone of 450G bearing. These kinds of wear morphologies were associated with abrasion and adhesion wear. In terms of PEEK composites, surface pit and fiber breakage were common wear features. Scale-like wear scars were only observed on the CA30 and FC30 bearings. Apart from fiber detachment induced material loss, adhesion wear was dominated in CA30 and FC30, while abrasive wear was more pronounced in GL30. Under bovine serum lubrication, no solid lubrication film was found. Moreover, wear process did not induce obvious change in surface layer crystallinity. The work conducted in this study provide the basic tribological knowledge of PEEK and its composites under physiologically relevant lubrication condition, which is helpful for the design and development of artificial prosthesis.