Effect of Debris on Fretting Wear Behavior of Ti-6Al-4V Alloy

By removing the debris after a certain number of fretting cycles, and preparing the surface texture to store more debris, the effect of debris on the fretting wear of Ti-6Al-4V alloy was studied. The fretting tests were conducted under different loads (from 15 N to 120 N) and different applied displacements (from 20 μm to 50 μm). It could be found that different from the usual understanding in the past, the removal of wear debris would cause a sudden drop in friction coefficient as well as the system deformation. The biggest drop reached 63% and 41% under the load of 20 N respectively. The drop of friction coefficient was caused by the reduction of the large particles of debris, while the small particles of debris still remained at the wear scar and played a role in reducing friction. The fretting loops would also change accordingly. After a certain number of cycles, the initiation and ejection of wear debris became balanced again, which led to that friction coefficient and system deformation reached the level before the debris was removed. When the groove surface textures perpendicular to the fretting direction were prepared on the surface of the Ti-6Al-4V alloy, a large amount of wear debris was trapped in the contact area by the grooves. This caused bigger friction coefficient and the system deformation. The maximum increase reached 21% and 47% under the load of 20 N respectively. After collecting the wear debris, the scanning electron microscope observation showed that the wear debris was loose granular, the size was concentrated between 0.2 μm and 1.5 μm, and most of them appeared agglomerated. The loose debris acted as a buffer between the two contact surfaces. As a result, the more debris led to the more obvious buffering effect as well as the bigger system deformation.