Influence of porosity on friction and wear of tetragonal zirconia polycrystal

Sliding wear properties of ultra-fine-grained (180 nm) yttria-doped tetragonal zirconia (Y-TZP) ceramics were examined with porosities from 1.5% to 7%. On a pin-on-plate tribometer under dry-N2 conditions, e.g., wear rates of the material increase by a factor of 5 by increasing porosity with a factor of 5 (from 1.5 to 7.0 vol%). In all cases no (irreversible) phase transformation to monoclinic zirconia took place during wear tests. The results for the relatively dense nanostructured materials showed significant evidence of plastic deformation and less microcrack formation. The morphology of the wear tracks in these ceramics indicate that the degree and amount of microcracks on the contact surface increased with porosity. A change in wear mechanism is observed.