Tribocorrosion behavior of S-phase surface engineered medical grade Co–Cr alloy

Abstract

Co–Cr alloy is one of the most widely used metallic biomaterials for metal-on-metal joint prostheses. However, concerns about increased revision rates associated with large head metal-on-metal replacements have been raised recently. Release of such toxic ions as Cr and Co from corrosion–wear induced nano-sized wear debris has been envisaged as the potential cause. This research was aimed at studying the tribocorrosion behavior of S-phase surface engineered medical grade ASTM F1537 Co–Cr alloy with a view of addressing problems associated with current metal-on-metal joint prostheses.To this end, ASTM F1537 Co–Cr alloy surfaces were plasma alloyed with carbon at low-temperature to produce a surface carbon S-phase layer, which is a precipitate-free carbon super-saturated solid solution with high hardness, good corrosion and wear resistance. Cyclic potentiodynamic and potentiostatic measurements were performed under unidirectional sliding wear condition in 1M Ringer's solution to evaluate tribocorrosion properties of the low temperature plasma treated as well as untreated ASTM F1537 Co–Cr alloy.The results showed that the S-phase layer can significantly enhance the tribocorrosion properties of Co–Cr alloy in terms of reduced corrosion potentials and wear volume. The much improved tribocorrosion behavior of the S-phase layer can be attributed to its high hardness, good corrosion resistance and excellent repassivation ability.