Tribological characterization of bioactive zirconia composite layers on zirconia structures

The aim of this paper was to evaluate the tribological performance of bioactive zirconia composite layers applied by press and sinter method on yttria-stabilized zirconia (YSZ) substrates. Two types of bioactive zirconia composite layers were tested, zirconia reinforced by 10 vol% of HAp and by 10 vol% of beta-TCP. The wear tests were carried out in Phosphate Buffered Saline (PBS) solution at 37 +/- 2 degrees C using a ball-on-plate configuration. The wear mechanisms of the samples were identified by SEM/EDS. Fracture toughness, hardness and roughness were also evaluated. Results indicated that the tribological performance was not affected by the addition of bioactive materials. The specific wear rates were within the same order of magnitude and no change in the coefficient of friction was observed among all samples. These results show that this new approach based on the use of a bioactive zirconia composite layer on zirconia substrate, is a promising solution for implants, as it is possible to maintain the high tribological properties of zirconia and in the same time to improve bond between living tissue and implant, as the HAp and beta-TCP are acting as bioactive sites.