The influence on corrosion of Melt Growth Composites (MGC) such as Al_2O_3/Y_3Al_5O_<12> (YAG), Al_2O_3/GdAlO_3 (GAP) or Al_2O_3/Er_3A1_5O_<12> (EAG) was investigated at 1500℃ in a high water vapor pressure environment for time up to 800h. There was observed the flexural strength, the fracture surface, the surface roughness and the microstructure changes after corrosion tests. The strength degradation was seen the strength decreased down to about 69〜75% after corrosion test at 1500℃ in PH20=150kPa up to 800h. The fracture surface showed that the fracture was initiated at surface flaws due to etching by corrosion. The surface roughness increased with increasing corrosion time. The Al_2O_3/GAP system was seen the broad peak (100〜1200cm^<-1>) of Raman spectrum, which caused the microstructure changed into amorphous phases.
