Extensive progress has been made in the development of high performance silicon nitride structural ceramics and component fabrication. This has in turn led to a number of successful applications in small turbines, including commercial aircraft production components and a number of successful tests and continuing field tests in aircraft auxiliary power units, air turbine starters, and stationary power generation engines. The current status, capabilities, limitations, and material refinement efforts for silicon nitride at AlliedSignal Ceramic Components (ASCC) will be presented, including environmental durability and environmental barrier coating investigations. Two key issues in the implementation of silicon nitride turbine components have been the ability to fabricate engine quality hardware, and fabrication at low-enough costs to allow commercialization. The current status of production forming processes will be presented and the development of new low cost forming and advanced technologies including gelcasting and solid freeform fabrication will be discussed, both in regards to component fabrication capability and production cost potential. Finally, the status of a number of commercial and development applications such as propulsion turbine engine seals, APU hot section wheels, blades, and nozzles, industrial turbine nozzles, and power generation microturbine components will be discussed.
Development of Silicon Nitride Engine Components for Advanced Gas Turbine Applications