This paper provides a review of a recent study undertaken to examine the mechanical and thermal stability of silicon nitride ceramic nozzles exposed in an industrial gas turbine. The average temperature and pressure of gas entering the vanes were approximately 1066°C and 8.9 atm, respectively. The total exposure time was 815 h including a 22 h shakedown test. Scanning electron microscopy was used to elucidate the changes in the microstructures arising from the oxidation process. The recession of the airfoils arising from the volatilization of the normally protective silica layer was also measured. The stability of the intergranular phases was evaluated using x-ray diffraction. The surface strength was measured using a miniature biaxial test specimen which was prepared by diamond core drilling.

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