The Brittle Materials Design, High Temperature Gas Turbine program is to demonstrate successful use of brittle materials in demanding high temperature structural applications. A small vehicular gas turbine and a large stationary gas turbine, each utilizing uncooled ceramic components, will be used in this iterative design and material development program. In the vehicular turbine project, Weibull theory was utilized to predict failure probabilities of monolithic hot pressed silicon nitride turbine rotors, including the effects of varying disk contours. Good agreement with theory resulted from strength testing of silicon nitride bars and disks. Processing parameters were established for the fabrication of multi-density rotors, and a number of prototype rotors were spin tested. Thermal response of stator vanes during engine operation was determined directly using a quartz window in a stator test rig. Improvements in properties were made for both injection molded and slip cast reaction sintered silicon nitride. In the stationary turbine project, a major objective was achieved when the first static rib test of hot pressed silicon nitride stator vanes was completed at temperatures up to 2200 F. Although some vanes failed due to out-of-tolerance final machining of critical interfaces, it was encouraging that two vanes which were subjected to the higest temperatures and most severe transient effects were not damaged. Additional information was also generated on the properties and corrosion resistance of hot pressed silicon nitride.
Interim rept. no. 5, 1 Jul-31 Dec 1973
Prepared in cooperation with Westinghouse Electric Corp., Pittsburgh, PA