Investigation of Ceramics for High-Temperature Turbine Vanes.
Final rept. 20 Mar-19 Dec 73,
GENERAL ELECTRIC CORPORATE RESEARCH AND DEVELOPMENT SCHENECTADY N Y
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Large tubular crystals of alpha-SiC, which can become strength limiting, tend to grow during the hot-pressing boron containing beta-SiC powder. The exagerrated grain growth was controlled by several methods Stabilization of beta-SiC by nitrogen nucleation of alpha-SiC by seeding and, decreasing the hot-pressing temperature by using SiC powders with increased sinterability. Nitrogen doping was achieved by the addition of either Si3N4 or BN and yields electrically conductive materials which are amenable to electro discharge machining. The hot-pressing of large billets of nitrogen-doped materials revealed that specimen thickness and the applied pressure are critical parameters which affect the final density. Pressure-less sintering was achieved in submicron beta-SiC powders by the addition of boron and carbon. Results of microstructural examination, room temperature and high temperature bend strength, creep and impact tests are presented. Modified author abstract
- Ceramics, Refractories and Glass
- Jet and Gas Turbine Engines