Effect of contact pressure and load on wear of alumina

Wear experiments were conducted in air using self-mated alumina in a pin-on-disk configuration at different loads using balls of different diameters as pins to maintain a constant value of initial Hertzian pressure. The selected initial load was kept constant for the rest of the sliding. Wear volume on the ball and the apparent contact pressures were calculated from the measured wear sear diameters on the balls at regular sliding intervals. The results show reduction in wear coefficient with sliding distance, as the contact pressure reduces (due to increment in the contact area). However, a good correlation was observed between the normalized wear rate and the apparent contact pressure, irrespective of the applied load, sliding distance, ball diameter and apparent contact area. This observation is explained based on the assumption that besides the asperities that deform plastically a large portion of the asperities deforms elastically and carries the applied load. It is argued that for a mixed elastic/plastic contact the number of plastically loaded asperities, and therefore, the wear rate, should depend on the apparent contact pressure. (C) 2001 Elsevier Science B.V. All rights reserved.