Load-and time-dependent dry tribological behavior of quench-produced diamond coatings on commercially pure titanium

Abstract

Titanium and its alloys are extensively employed in biomedical implant applications owing to their excellent biocompatibility and corrosion resistance; however, their inherently poor tribological performance severely limits long-term reliability under load-bearing conditions. In this work, a highly adherent Quench-produced Diamond (Q-Dia) coating was deposited on commercially pure titanium using a hybrid coaxial arc plasma deposition (CAPD) technique combined with in situ Ar + plasma etching to enhance interfacial bonding. The resulting coating exhibits a dense nanocomposite architecture comprising nanodiamond crystallites embedded within an amorphous carbon matrix, which promotes strong coating–substrate adhesion, as evidenced by a high critical load (Lc₂) of 20.13 N determined from scratch testing. Dry sliding tribological tests against an Al₂O₃ counter-body revealed a substantial reduction in friction and wear compared with uncoated titanium. While bare titanium showed high and unstable coefficients of friction (0.497–0.567) accompanied by severe wear damage, the Q-Dia-coated surface achieved a low and stable steady-state friction coefficient of approximately 0.127 with no wear observed. Furthermore, electrochemical measurements conducted in simulated body fluid demonstrated a positively shifted corrosion potential for the Q-Dia coating (0.025 V ) relative to bare titanium (−0.324 V), indicating improved electrochemical stability. These findings demonstrate that Q-Dia coatings effectively mitigate the tribological limitations of titanium without compromising corrosion resistance, highlighting their strong potential for load-bearing biomedical implant applications operating under dry or boundary-lubricated conditions. • Hybrid CAPD enables room-temperature deposition of highly adherent (~3 μm) Q-Dia coatings on titanium. • Scratch testing reveals strong coating–substrate adhesion, with a high critical load of Lc₂ = 20.13 N. • Q-Dia coatings markedly enhance the tribological performance of pure titanium under dry sliding against Al₂O₃. • Extremely low steady-state friction coefficients down to 0.127 are achieved. • Superior wear resistance arises from a stable, carbon-rich tribo-layer formed via localized sp 3 -to-sp 2 rehybridization.