NO:WESTRUCTIVE INSPECTION OF HIGH PERFORMANCLCERAMICS

Two ceramic materials, a hot-pressed silicon nitride and a siliconized silicon carbide, ~/ere manu-factured 1~ith seeded particulates to evaluate the effectiveness of existing nondestructive test practices at AMf1RC for defect detection in ceramics and to evaluate the effect of inclusions upon material strength. The types of seeded defects were of greater and lower density relative to the matrix materials and ranged in size from approximately IJ.l mm to 0.6 mm. The nondestructive methods used in the i.nvestigation were ultrasonics, radiography, eddy current and penetrant. Bend bar specimens were cut from the seeded regions of the billets and tested at 25°C, 1093°C and l37l°C. Fracture oripins were examined by optical and elec-tron microscorv and by microprobe to correlate the nature of the fracture initiating defects with the non-destructively detected defects. This permitted a rankin ~ of defect detection sensitivity and defect ef-fect upon stren~th. SUf·1MARY Two billets approximately 15 centimeters square of each matrix material were prepared with seeded inclusion particles from standard produc