Investigation of Ceramics for High Temperature Turbine Components.
Final rept. 18 Oct 74-17 Oct 75,
GENERAL ELECTRIC CORPORATE RESEARCH AND DEVELOPMENT SCHENECTADY N Y
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The sintering kinetics of boron-doped SiC were studied in a high temperature dilatometer and discussed in terms of density and densification rate vs. temperature, time, sintering atmosphere, green density and initial crystallite size. A nitrogen furnace atmosphere was found to retard sintering and halt the Beta to alpha transformation. The fracture strength of sintered SiC was characterized in three-point bending as a function of powder processing technique, sintering atmosphere, density, and machining damage. The optimum powder processing included wet milling, screening 8 micrometers, spray freezing and freeze drying. Surface damage induced during machining could be repaired by an appropriate thermal treatment. The high temperature strength was measured in both bending and tension theta tensile specimens at 1600 C revealing exceptionally good resistance to subcritical crack growth. The response of sintered SiC to thermally induced stresses was tested by the Simulated Gas Turbine Environment Test of NASA and the Glenny Thermal Fatigue Test. Thermal stresses and probabilities of failure for the latter were computed by finite element analysis. Author
- Ceramics, Refractories and Glass
- Jet and Gas Turbine Engines