Abstract
High temperature and high pressure water corrosion behaviors of ZrO2-particle-dispersed Al2O3 composites were investigated in terms of with the microstructural changes and residual strength characteristics. Sintered Al2O3 bodies with 5, 15, and 30 wt.% 3 mol% Y2O3-doped tetragonal ZrO2 were made using a pressureless sintering method at 1 550. 1 600 and 1 650°C, respectively. These Al2O3/ZrO2 ceramic composites were corroded in high temperature and high pressure deionized water at 200°C∼300°C. Corrosion damage of the Al2O3/ZrO2 ceramic composites occurred preferentially on ZrO2 particles after long-term immersion in deionized water. The tetragonal to monoclinic phase transformation occurred in yittria-doped tetragonal ZrO2 polycrystals due to high temperature and high pressure deionized water corrosion. For improvement of the corrosion characteristics of the composites, are important increasing the ZrO2 content within a range in which no remarkable residual strength degradation is recognized and lowering of the sintering temperature. Al2O3/ZrO2 ceramic composites also have superior residual strength characteristics compared to monolithic ZrO2 ceramics. The residual strength characteristics are improved by increasing the ZrO2 particle concentration. and loweringthe sintering temperature. The fracture surface morphology change from transgranular to intergranular was brought about by increasing the ZrO2 content. Improvement in residual strength characteristics of Al2O3/ZrO2 composites was realized. due to intergranular crack propagation, crack pinning caused by remarkable grain bridging by Al2O3 and stress-induced transformation from tetragonal ZrO2 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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