Design and characterisation of a new duplex surface system based on S-phase hardening and carbon-based coating for ASTM F1537 Co-Cr-Mo alloy

Co-Cr-Mo alloys are one of the most widely used metallic biomaterials for metal-on-metal joint prostheses. However, concerns over increased revision rates mainly due to nano-sized wear debris have been raised. This study was aimed at enhancing the friction, wear and load-bearing properties of Co-Cr-Mo alloys by developing a new duplex surface system combining super hard and wear-resistant S-phase layer with self-lubricating, low-friction carbon-based coating. To this end, ASTM F1537 Co-Cr-Mo alloy surface was plasma carburised (PC) at 450 °C and then coated with a carbon-based GiC coating. The microstructures of the duplex and single treated (PC or GiC coating) Co-Cr-Mo surface systems were characterized and their mechanical, tribological and corrosion properties were evaluated. The results showed that the new duplex surface system exhibited a high load bearing capacity, a low friction coefficient, excellent wear resistance and good corrosion behaviour.