Sliding friction and wear of alumina-reinforced zirconia-toughened mullite composites

The friction and wear characteristic of self-mated alumina-reinforced zirconia-toughened mullite (ZTM/A) composites has been investigated using a block-on-ring tribometer in different lubricants at varying loads. Load-dependent wear transitions were observed for these ceramics. The wear transition was usually accompanied by an abrupt change of friction coefficient and wear rate. The addition of Al2O3 effectively reduces the wear rate of ZTM/A composites before the wear transition in water and at middle loads in machine oil. Scanning electron microscope (SEM) micrographs show that the main pre-transition wear mechanism of ZTM/A composites is plastic deformation, ploughing and occasionally grains pulling out, while fracture is the dominant mechanism of post-transition. Al2O3 can restrain the t→m phase transformation of zirconia to some extent and improve the resistance of these materials to wear by fracture, ploughing and plastic deformation.