Wet erosive wear of alumina densified with magnesium silicate additions

A study was made of the wet erosive wear of polycrystalline alumina of mean grain size >1 mum, containing up to 10 wt% of magnesium silicate sintering aid. For pure polycrystalline alumina, the dominant wear mechanism was gra in-boundary microfracture, leading to partial or complete grain removal. In the case of the liquid-phase-sintered materials, wear rates could be as lo w as 25% of those of pure alumina of the same mean grain size, and the main material removal mechanism was transgranular fracture combined with triboc hemical wear. The use of Cr3+ photoluminescence line broadening showed much higher levels of local stress in the magnesium silicate-sintered materials (similar to 450 MPa) than in the pure-alumina materials (similar to 200 MP a). Grain-boundary compressive hoop stresses, caused by the thermal expansi on mismatch between a continuous magnesium silicate film and the alumina gr ains, provided an explanation for the improved wear resistance of the alumi na sintered with magnesium silicate.