Improving the Reliability of Silicon Nitride: A Case Study

Abstract

Recent AGT engine test data indicate that, in prototype quantities, structural ceramics can be made capable of meeting the stringent mechanical constraints imposed by the turbine environment. Questions remain to be answered about the long-term capabilities of structural ceramics and their reliability in production quantities. The reliability of structural ceramics can be enhanced in three ways: by careful processing, improving fracture toughness using composites, and by appropriate NDE/proof-testing. Data generated by research in all three areas suggest that none of these alone is a panacea for the reliability problem. However, taken in combination, these data suggest that the necessary levels of reliability can be attained even in production ceramic turbine rotors. Research results on GTE AY6 sintered Si{sub 3}N{sub 4} are presented to support this viewpoint.