Mirror finishing of Co–Cr–Mo alloy using elliptical vibration cutting

The biocompatibility and fatigue strength of Co–Cr–Mo alloy are excellent, making it suitable for the use in artificial joints. The head of an artificial joint must have a mirrored surface to reduce abrasive resistance. Mirror finishing of Co–Cr–Mo alloy with single-crystal diamond cutting tools is hindered by microchipping of the tool edge. It is generally believed that microchipping of diamond tools is caused by work hardening of the Co–Cr–Mo alloy during the cutting process. In the present research, mirror finishing of Co–Cr–Mo alloy was carried out using elliptical vibration cutting, as well as by ordinary cutting. The experimental results show that elliptical vibration cutting offers superior performance compared to ordinary diamond cutting without tool vibration. Microchipping, tool wear, and work hardening were all significantly reduced. A fine mirrored surface (with maximum surface roughness under 25 nmP-V) was maintained up to a cutting length of about 14 m. As a practical consequence, elliptical vibration cutting was successfully applied to the mirror finishing of a femoral head.