INFLUENCE OF POROSITY ON FRICTION AND SLIDING WEAR OF TETRAGONAL ZIRCONIA POLYCRYSTAL

Microstructures of yttria-partially-stabilized zirconia containing up to about 15% porosity were produced by sintering. Wear tests were carried out on these ceramics in dry sliding and oscillating sliding contacts in air at ambient temperatures by using block-and-ring geometries. In addition, sliding wear tests were run under conditions of boundary lubrication by water. The microstructures and worn surfaces were extensively analysed using scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. Depending on the test conditions, the friction coefficient was either independent of porosity or increased above about 7 vol.% of pores. The wear intensity was slightly reduced by a small amount but substantially increased by greater amounts of porosity. The coefficient of friction decreased but the wear intensity increased with increasing normal loads. The presence of water enhanced both the friction and wear of dense and porous specimens.