Fabrication of Ceramic Components for Advanced Gas Turbine Engines

High quality, reliable ceramic components are required in the Garrett/Ford AGT101 program. The purpose of this program is to demonstrate the feasibility of achieving high efficiency in a ceramic gas turbine engine. AiResearch Casting Company (ACC) has supplied most of the ceramic components qualified for testing in the AGT101 program. These components include turbine rotor, stator, shroud, inner/outer diffuser and seal ring. Except the stator, the fabrication process used is slip casting of silicon or silicon nitride powders to produce reaction bonded or sintered components.

The recent high yields (> 80%) in fabrication of the above slip cast components at ACC were primarily accomplished by a better understanding of the effects of processing parameters on the microstructure and properties of the finished parts. The parameters studied include powder particle size distribution, casting slip viscosity, pH and solid content. Examples illustrating the relationships between processing parameters and the microstructure and properties of the finished parts are presented. The green components were consolidated by nitriding, sintering or sinter/HIP. The results of the recent sinter/HIP developments are discussed.