S. Ran

A wear-resistant zirconia ceramic for low friction application

A high wear-resistant ceramic/ceramic couple is described associated with low friction. By adding a small amount CuO to yttria-doped tetragonal zirconia (Y-TZP) the (dry) coefficient of friction against alumina is only 0.2 during a sliding distance of 3-5 km after which the coefficient drastically increases and a transition from mild to sever wear occurs. Pure Y-TZP exhibits a coefficient of friction of 0.7 under the same experimental conditions but wear remains mild during the test (upto 10 km of sliding distance). These small amounts of CuO also strongly influence the densification behaviour. Sintering of this system occurs in several steps where amng other things dissolution of CuO in the Y-TZP matrix as well as liquid phase sintering takes place. Non-uniform shrinkage of the CuO-doped system resulting in relative large microcracks in the ceramic can explain its sudden drastic increase in coefficient of friction and wear rate after 3-5 km of operation.