Dual-rotary fretting wear of 7075 alloy in media of oil and water

Dual-rotary fretting (DRF) is a complex fretting wear mode combining torsional mode with rotational mode. With the contact configuration of ball-on-flat (7075 aluminum alloy flats against AISI 52100 steel balls), the DRF wear tests in oil and water were carried out respectively under varied rotary angular displacement amplitudes and tilt angles. By combining the dynamic behavior analyses with damage morphology examinations, the wear mechanisms of DRF in dry condition, oil and water were analyzed in detail. Compared with the dry friction condition, both oil and water acted as lubricants and played an important role during the running and damage processes of DRF, which significantly changed the fretting running regimes and third-body behaviors. It is found that the oil media can effectively mitigate DRF damage, especially when the tilt angle and the angular displacement amplitude are large, because the oil can penetrate into the contact interface and form a lubricant film. Relatively, the water can easily penetrate into the micro-cracks on the surface and promote the propagation of cracks because the viscosity of water is low. Therefore, the delamination is more obvious in the water.