Strength of Slip‐Cast, Sintered Silicon Nltrlde

The flexural strength of slip‐cast, sintered silicon nitride was evaluated as a function of temperature (20° to 1300°C in air), applied stress, and time. The flexural strength was independent of temperatures from 20° to 800°C, and the mode of crack propagation was primarily transgranular. Above 800°C, the flexural strength decreased because of viscous flow of the glassy phase present in the material resulting in subcritical crack growth (SCG). The mode of crack propagation during SCG was essentially intergranular. Flexural stress‐rupture evaluation in the temperature range 800° to 1000°C was used to identify the stress levels for time‐dependent and time‐independent failures.