Sliding Wear Properties of Sintered Mullite Ceramics

Abstract

The sliding wear properties of mullite and mullite/ZrO2 composite ceramics have been investigated with a pin-on-disk wear tester using Al2O3, Si3N4 or SiC as the disk material. There was no remarkable difference in the specific wear rate and coefficient of friction of two mullite ceramics. These sliding wear properties were independent of the particle size and its distribution of mullite. On the other hand, the specific wear rate decreased in the case of mullite/ZrO2 composite as the pin and Al2O3 as the disk material. These results suggested that dropped-out ZrO2 particles might lubricate at the interface, when the hardness of the pin was similar to that of the disk material. Wear mechanism was roughly classified to three patterns from the observation of frictional surface, which mainly depended on the sliding velocity. For pattern I, the surfaces of pin and disk were smooth and the wear rate of pin depended only on the load. For pattern II, the adhesion and spark caused by the heat of friction were observed. For pattern III, microfracture due to lateral crack was mainly observed, therefore the wear mechanism was explained by the indentation fracture model. The wear rate of mullite ceramics could be estimated only with their mechanical properties under the same sliding condition.