Effect of temperature on dynamic fatigue behaviour of Si₃N₄ material

The dynamic fatigue behaviours of Si₃N₄ material at room temperature, 800 and 1100°C were investigated. It was discovered that the fracture strength decreases with the increase of σ at a high stress rate, and that the stress corrosion exponent n decreases also with the temperature increasing. The former is the same as that in transformation toughening ceramics and glass-ceramics, but is of some deviation from the theoretical prediction. The fractographic observation showed that the dynamic fatigue failure mechanism of Si₃N₄ at elevated temperature is the softing of the glass phase in grain boundaries.