Fabrication and Characterization of MGC Components for Ultra High Efficiency Gas Turbine

Abstract

Much attention has been paid to unidirectionally solidified ceramic composites as a candidate for a high-temperature structural material. We have recently developed eutectic composites, which are named as Melt Growth Composites (MGCs). The binary MGCs (Al 2 O 3 /YAG and Al 2 O 3 /GAP binary systems) have a novel nucrostructure, in which continuous networks of single-crystal Al 2 O 3 phases and single-crystal oxide compounds (YAG or GAP) interpenetrate without grain boundaries. Therefore, the MGCs have excellent high-temperature strength characteristics, high creep resistance, superior oxidation resistance and thermal stability in the air atmosphere at very high temperatures. Manufacturing processes for the MGCs are being examined under a Japanese national project, scheduled from 2001 - 2005. To achieve higher thermal efficiency for gas turbine systems, bowed stacking nozzle vanes have been fabricated on an experimental basis. The steady state temperature and thermal stress distribution on the surface of the bowed stacking nozzle have been analyzed. In addition, some properties of MGC components such as the thermal stability in an air atmosphere and the stability in water vapor at elevated temperatures are reported.