Brittle Materials Design, High Temperature Gas Turbine

Abstract
The demonstration of uncooled brittle materials in structural applications at 2500 F is the objective of the 'Brittle Materials Design, High Temperature Gas Turbine' program. Ford Motor Company, the contractor, is utilizing a small vehicular gas turbine comprising an entire ceramic hot flow path including the highly stressed turbine rotors. Westinghouse, the subcontractor, originally planned to evaluate ceramic first stage stator vanes in an actual 30MW test turbine engine; however, this objective was revised to demonstrate ceramic stator vanes in a static test rig. Both companies had in- house research programs in this area prior to this contract. In the stationary gas turbine project, the test of ceramic stator vanes in a static rig for 100 cycles up to temperatures of 2500 F has been completed. This accomplishment meets the revised objectives for the stationary turbine project and, therefore, this project was completed. Fabrication of duo-density silicon nitride turbine rotors continued during this reporting period. The injection molding of duo- density rotor blade rings has been improved by the addition of a solid state automatic control system which was installed on the injection molding machine. Fabrication of turbine inlet nose cones and stators was resumed on a limited basis. In order to select the best method of processing Si3N4 powder, the optimum Mg0 content and the best hot pressure parameters consistent with the hub forming portion of the duo-density rotor process, a parametric processing study was conducted. A technique was developed which allows the furnace to control the nitriding dependent upon the nitrogen gas consumption rate, resulting in improved material structure.