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Brittle Materials Design, High Temperature Gas Turbine. Volume 2. Ceramic Turbine Rotor Technology

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Interim rept. no. 12, Jan-Sep 1977

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The progress in the last nine months on ERDA supported programs within the joint DARPAERDA supported Brittle Materials Design, High Temperature Gas Turbine Program is reported on in this volume. Volume 1 covers the progress on the DARPA supported Ceramic Turbine Testing Program. Investigations of the materials used to fabricate duo-density ceramic turbine rotors were conducted on injection molded reaction bonded and hot pressed silicon nitride. The injection molding process, utilized to fabricate rotor blade rings, was improved by optimizing the molding parameters with the automated control system and improving the molding mixture. The installation of nozzles, to apply mold release, and air blast jets, to clean the die and evenly distribute the mold release, resulted in a noticeable improvement in the surface finish of the blade rings. Duo-density turbine rotors were tested in the cold spin pit to evaluate the hot press to reaction sintered bond joints and the effect of I.D. voids, in the blade ring rim, on blade failure speeds. Degradation of the room temperature strength of the reaction bonded silicon nitride rotor blades was identified as resulting from the press-bonding operation. A procedure for determining whether statistically significant differences exist between two sets of data, known as the Hypothesis Testing was outlined. The test was applied to data from duo-density turbine rotors and showed that blade strength did deteriorate after the press-bonding operation. Use of proof-testing as a means of enhancing the accuracy of life predictions was discussed.

Subject Categories:

  • Ceramics, Refractories and Glass
  • Jet and Gas Turbine Engines

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