High temperature and high pressure water corrosion behaviors of ZrO
2-particle-dispersed Al
2O
3 composites were investigated in terms of with the microstructural changes and residual strength characteristics. Sintered Al
2O
3 bodies with 5, 15, and 30 wt.% 3 mol% Y
2O
3-doped tetragonal ZrO
2 were made using a pressureless sintering method at 1 550. 1 600 and 1 650°C, respectively. These Al
2O
3/ZrO
2 ceramic composites were corroded in high temperature and high pressure deionized water at 200°C∼300°C. Corrosion damage of the Al
2O
3/ZrO
2 ceramic composites occurred preferentially on ZrO
2 particles after long-term immersion in deionized water. The tetragonal to monoclinic phase transformation occurred in yittria-doped tetragonal ZrO
2 polycrystals due to high temperature and high pressure deionized water corrosion. For improvement of the corrosion characteristics of the composites, are important increasing the ZrO
2 content within a range in which no remarkable residual strength degradation is recognized and lowering of the sintering temperature. Al
2O
3/ZrO
2 ceramic composites also have superior residual strength characteristics compared to monolithic ZrO
2 ceramics. The residual strength characteristics are improved by increasing the ZrO
2 particle concentration. and loweringthe sintering temperature. The fracture surface morphology change from transgranular to intergranular was brought about by increasing the ZrO
2 content. Improvement in residual strength characteristics of Al
2O
3/ZrO
2 composites was realized. due to intergranular crack propagation, crack pinning caused by remarkable grain bridging by Al
2O
3 and stress-induced transformation from tetragonal ZrO
2 to stable monoclinic in the vicinity of the crack tip. Then, the necessary manufacturing conditions for sustaining the improved strength characteristics after high pressure and high temperature water immersion were clarified. In addition design concepts used to obtain water-corrosion-resistant high strength and high toughness particle dispersed ceramic composites were proposed.
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