Abstract: The tribological behavior of the CoCr28Mo/CoCr28Mo pair was studied using pin-on-disc tribometer. Four bio-lubricants were re-tained including pure sesame oil, nigella oil, physiological solution (0.9% NaCl) and Hyalgan®. Hyalgan® is a sodium hyaluronate
(20 mg/2 mL) pharmaceutical intra-articular injection used, in this study, as a reference. The Coefficient of Friction (CoF) and wear rate (K) of CoCr28Mo were computed after tribological tests. The tribological efficiency of vegetable oils with regard to their chemical compo-sition and structure was compared to Hyalgan. It is found that, the use of vegetable oils enhanced significantly the tribological behavior of CoCr28Mo/CoCr28Mo pair. The obtained results were correlated to the chemical structure of vegetable oils namely the Unsaturations Number (UN) of fatty acids constituting the oil. Microscopic and chemical characterization of CoCr28Mo pins and discs were conducted and the wear mechanism was discussed.

Key words: friction coefficient, wear resistance, oil lubrication, CoCr alloy