Influence of fretting regimes on the tribocorrosion behaviour of Ti6Al4V in 0.9 wt.% sodium chloride solution

The effect of displacement amplitude, normal force and tribometer stiffness on the tribocorrosion response of a Ti6Al4V alloy in contact with a smooth alumina ball was investigated using a fretting corrosion rig equipped with an electrochemical cell. The roughness of the alloy plates was 0.6 μm, typical for the surface of hip joint stems. All experiments were carried out in 0.9 wt.% NaCl under anodic polarisation at a potential of 0.5 V versus the silver–silver chloride reference electrode, corresponding to the passive potential region. Anodic current, load, friction force and displacement amplitude were monitored in real time. Wear volume and surface morphology were evaluated at the end of fretting experiments. Results show that the prevailing fretting regime critically affects the overall system behaviour. Only fretting regimes involving slip led to measurable wear and to an enhancement of the anodic current. Previously developed tribocorrosion models for passivating metals were found to well describe the effect of normal force and displacement amplitude on the anodic current.