Stress-corrosion cracking in alumina ceramics

Strength deterioration of oxide-base ceramics in humid environments is well-known phenomenon, which arouses interest with respect to the performance and reliability of various engineering parts. Experiments are performed with aluimina ceramics bonded with various grain-boundary phases. The specimens were tested for bending strength in water, acidic and basic aqueous solutions at a constant loading rate and in the wide loading rate range (dynamic fatigue tests). Features of the environmental effects on strength are studied in dependence on both the nature of the grain-boundary phase and the environment. Competitive contributions from the Rebinder effect and the chemical stress-corrosion cracking to the strength degradation of aluminas are revealed and discussed. The ratio of these contributions is dependent on the grain-boundary phase composition. Method to inhibit the delayed failure in a glass-bonded alumina is proposed.