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This is a two-part paper, which stresses the materials science approach to understanding dust erosion mechanisms. The first part is an experimental phase, studying the effects upon solid-particle erosion, of such material and environmental variables as target alloy composition and heat-treat condition; dust particle velocity, size, concentration, velocity, and kinetic energy; carrier-gas true temperature and impingement angle. All test variables and their limits were chosen to simulate the range of engineering conditions and erosive environments encountered in helicopter turbine service. Actual erosion data are compared with erosion levels predicted by existing theories on particulate erosion. The second part is a diagnostic phase, programmed to detect and study visible phenomena associated with the erosion processes, using high-magnification electron microscopy. Phenomenological evidence obtained from the erosion surfaces and erosion products are used to define probable physical models of the erosion mechanisms.

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Task 3-V i s c o e l a s t i c Damping o f lass-Bonded 9 Ceramics 2.4 Task 4-Crack Arrest a n d Crack D i v e r s i o n by. . 10 J o i n t s 2.5 Task 5-Improved J o i n i n g and F a b r i c a t i o n Methods. 11 PROGRAM STATUS 13 3.1 Task 1-Long-Term J o i n t S t a b i l i t y 13 3.2 Task 2-D e t e r m i n a t i o n o f E n v i r o n m e n t a l a n d 19 S e r v i c e E f f e c t s o n. J o i n t ~e i i a b i l i t~ 3.3 Task ' 3-V i s c o e l a s t i c Damping o f G l a s s Bonded 19 Ceramics 3.4 ' Task 4-Crack Arrest a n d Crack D i v e r s i o n by 2 3 J o i n t s 3.5 Task 5-Improved J o i n i n g and F a b r i c a t i o n Methods 23