Uniaxial Tensile and Flexural Stress Rupture Strength of Hot‐Pressed Si3N4

Abstract

Uniaxial tensile stress rupture testing of hot‐pressed silicon nitride NC‐132 was carried out at 1000°, 1200°, and 1300°C in air at various applied stress levels and the corresponding times‐to‐failure were measured. Fracture occurred from both surface and internally initiated flaws. Fractographic evidence for failure‐initiation sites and the associated presence of subcritical (slow) crack growth are presented. Limited flexural stress rupture tests at 1200°C in air were also carried out and the data are compared. The uniaxial tensile and flexural stress rupture tests are much more sensitive in revealing the time‐dependent crack‐growth behavior than flexural stress rate tests.