MICROSTRUCTURE AND TRIBOLOGICAL PROPERTIES OF ZRO2 CERAMICS

The effect of sliding velocity on the tribological properties of zirconia-based ceramics, two yttria partially stabilized zirconia and a zirconia-alumina composite, slid against a high-purity, high-density alumina, were investigated using a pin-on-disc tribometer. The materials were tested at three different sliding velocities (0.3, 0.7 and 1.0 m s-1) with a normal load of 33.47 N and a distance travelled of 3000 m. Under the test conditions all the couples showed rather low values of the coefficient of friction. At 0.3 and 0.7 m s-1, the zirconia discs showed greater wear than the zirconia-alumina composite discs. Worn surface analysis, using a scanning electron microscope equipped with an energy dispersive X-ray attachment, showed that the wear mechanism is a complex process involving abrasive phenomena, brittle fracture, plastic deformation and zirconia transferred on to high-density alumina pins.