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 μm, containing up to 10 wt% of magnesium silicate sintering aid. For pure polycrystalline alumina, the dominant wear mechanism was grain‐boundary microfracture, leading to partial or complete grain removal. In the case of the liquid‐phase‐sintered materials, wear rates could be as low as 25% of those of pure alumina of the same mean grain size, and the main material removal mechanism was transgranular fracture combined with tribochemical wear. The use of Cr3+ photoluminescence line broadening showed much higher levels of local stress in the magnesium silicate‐sintered materials (∼450 MPa) than in the pure‐alumina materials (∼200 MPa). Grain‐boundary compressive hoop stresses, caused by the thermal expansion mismatch between a continuous magnesium silicate film and the alumina grains, provided an explanation for the improved wear resistance of the alumina sintered with magnesium silicate.