NDE Reliability and Process Control for Structural Ceramics

Abstract

The reliability of microfocus x-radiography and scanning laser acoustic microscopy for detecting microvoids in silicon nitride and silicon carbide was statistically evaluated. Materials and process-related parameters that influenced the statistical findings in research samples are discussed. The use of conventional x-radiography in controlling and optimizing the processing and sintering of an Si3 N4 -SiO2 -Y2 O3 composition designated NASA 6Y is described. Radiographic evaluation and guidance helped develop uniform high-density Si3 N4 modulus-of-rupture bars with improved four-point flexural strength (857, 544, and 462 MPa at room temperature, 1200°C, and 1370°C, respectively) and reduced strength scatter.