Sliding friction and wear behavior of two different grain-size aluminas （average grain size = 0.6 and 2 μm） was studied in physiological saline environment. Relationship between time and wear loss was observed. The wear loss volume increased with increased sliding time and fine-grained alumina exhibits a lower value. In the initial wear-in period, grains pull-out caused by grain-boundary microcracking is the dominant wear mechanism of submicron grained alumina. In the case of alumina of large grain size, intergranular and transgranular fracture is the basic wear mechanism. As the sliding time increases, compaction of wear debris on sliding surface of fine and coarsen alumina determines the wear characteristics.
