Percolative mechanism of sliding wear in alumina/zirconia composites

In the present study, the wear resistance of zirconia-toughened alumina (ZTA) composites has been investigated under dry sliding conditions with a Hertzian contact pressures from 1.1 up to 2.2 GPa and a sliding velocity of 0.15 m/s. The wear rate for composite with 22 vol.% zirconia (3Y-TZP) content at the lower contact pressures (1.1 GPa), was found to be around two orders of magnitude higher than the ones corresponding to 14 and 7 vol.% 3Y-TZP content. This result has been explained in terms of the infinite cluster formed at the percolation threshold. Above the critical 3Y-TZP fraction of ≈16 vol.%, corresponding to the percolation threshold, a continuous path between zirconia particles takes place. In these particular cases, the wear is dominated by a percolative mechanism so that the t → m zirconia transformation creates a microcracks network, which controls the wear resistance of the composite.