Effect of angular displacement amplitude on the torsional fretting corrosion behavior of CoCrMo alloy in different synovial fluid

The T-theta curves, friction torque curves, impedance and morphology were measured to research the effect of angular displacement amplitude on the torsional fretting corrosion behavior of the CoCrMo alloy in different synovial fluids. The results showed that the torsional fretting process could be divided into a running-in stage, a fluctuate stage and a steady-state stage both in NS and FBS. When the friction process was stable, the twisting fretting process of CrCoMo alloy was in the partial slip stage at theta = 2 degrees and in the gross slip stage at theta = 6 degrees, and the friction energy dissipation increased with the increase of theta. The results of electrochemical impedance spectroscopy showed that the impedance of the CoCrMo alloy decreased with the increase of theta, and when theta was larger, the decrease of impedance was more obvious. Also, the decrease of impedance in FBS was more obvious than that in NS. The surface roughness of CoCrMo after wear was enlarged with the increase of theta. The wear zone was extended to the central parts from the edge of the contact area, and wear was also severe in the central parts at a large value of theta. In NS, there was an obvious curved furrow at the edge of wear zone, and the roughness was much larger than that in FBS.