The hot-corrosion behavior of Al2O3, Lu2O3, mullite and Lu2Si2O7 phases were examined at 1500 degrees C. In the case of Lu2O3, no phase change was observed and no anisotropical corrosion occurred. In the case of the Lu2Si2O7 phase, anisotropic corrosion was observed. The Lu2Si2O7 crystal grains were well sustained to the hot-corrosion, however, the sodium element diffused though the boundary phase and anomalous grain growth occurred. On the other hand, in the case of Al2O3, the grains at the bulk surface corroded anisotropically. The corroded grain had a characteristic morphology as terrace field. In the case of mullite, the surface of the bulk was decomposed to the Al2O3 phase and the silica component was completely removed from the bulk surface. The sodium ions diffused though the sample during the corrosion test.

Keywords: hot corrosion; silicates; mullite; Al2O3