Ultrasonic NDE of structural ceramics for power and propulsion systems

Abstract

N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n Lewis Research C e n t e r Cleveland, O h i o 44135and George Y. Baak.1 i n i C l e v e l a n d S t a t e U n i v e r s i t y Cleveland, O h i o 44112 SUMMARYA r e v i e w i s p r e s e n t e d on r e s e a r c h i n v e s t i g a t i o n s o f s e v e r a l u l t r a s o n i c e v a l u a t i o n t e c h n i q u e s a p p l i c a b l e t o s t r u c t u r a l ceramics f o r advanced h e a t e n g i n e s . T h i s r e v i e w h i g h l i g h t s r e c e n t work conducted under t h e s p o n s o r s h i p o f and a t t h e Lewis Research C e n t e r . R e s u l t s o b t a i n e d w i t h scanning a c o u s t i c microscopy, scanning l a s e r a c o u s t i c microscopy, p h o t o a c o u s t i c m i c r o s c o p y , and s c a n n i n g e l e c t r o n a c o u s t i c microscopy a r e compared. I i m a g i n g t e c h n i q u e s , m i c r o s t r u c t u r e c h a r a c t e r i z a t i o n b y a n a l y t i c a l u l t r a s o n i c s i s d e s c r i b e d . The t e c h n i q u e s were e v a l u a t e d b y a p p l i c a t i o n t o r e s e a r c h samples of m o n o l i t h i c s i l i c o n n i t r i d e and s i l i c o n c a r b i d e i n t h e form o f d i s c s and b a r s c o n t a i n i n g n a t u r a l l y -o c c u r r i n g and d e l i b e r a t e l y -i n t r o d u c e d f l a w s and m i c r os t r u c t u r a l anomalies. S t r e n g t h s and l i m i t a t i o n s o f t h e t e c h n i q u e s a r e d i s c u s s e d .