ALONとその複合セラミックス

抄録

ALON was successfully consolidated by pressureless sintering of a powder mixture of 70mol% Al₂O₃ and 30mol% AlN, a composition in the single ALON phase region in the Al₂O₃-AlN system. BN was incorporated (0-50vol%) into the ALON, and ALON-BN composites were also consolidated by the pressureless sintering. In both cases, Y₂O₃ was added (4-8vol%) as a sintering aid. The relative density of the sintered bodies was higher than 90%. Reduction of the density due to BN addition was compensated by adjusting the amount of Y₂O₃. In the bending tests, ALON and its composite ceramics exhibited excellent high temperature properties. The strength of these ceramics did not decrease until 1400°C (1673K), and then decreased gradually to about 100MPa at 1600°C (1873K). ALON-BN composite exhibited the lowest erosion rate (<2μm/min) in molten steel (low carbon Al-killed) in comparison with sialon, Al₂O₃, ZrB₂ and AlN. The thermal shock durability was also improved by the incorporation of BN. Microstructural analysis showed that the high temperature integrity of the ALON and its composite ceramics are attributed to the existence of the grain boundary crystalline yttrium aluminium garnet (YAG) phase.