Compressive creep and creep failure of 8Y(2)O(3)/3Al(2)O(3)-doped hot-pressed silicon nitride

The compressive creep properties of hot-pressed Si3N4-8Y(2)O(3)-3Al(2)O(3) (wt%) have been investigated in the temperature range of 1543-1603 K in air, The stress exponent, n, of the power creep law was determined to be 1.5, and the activation energy was determined to be 650 kJ/mol. Transmission electron microscopy observations showed that grain-boundary sliding occurred with cavitation formation in the grain-boundary glassy phase. The quasi-steady-state creep results were consistent with that of the diffusion-controlled solution-diffusion-precipitation creep mechanism, and the distinguished failure mechanism was cavitation creep damage controlled by the viscosity of the boundary glassy phase, The compressive creep failure time, obtained at 1573 K, in the stress range of 175-300 MPa, followed the Monkman-Grant relation, indicating that cavity growth was mainly controlled by the creep response of the material.