The effects of cerium on the microstructure of INCO 901 superalloy
- PDF / 2,067,040 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 97 Downloads / 174 Views
IN c h a r a c t e r i z i n g
the m i c r o s t r u c t u r e s of n i c k e l and i r o n - b a s e s u p e r a l l o y s , the v a r i o u s p r e c i p i t a t e d p h a s e s and t h e i r effects upon the n i c k e l - i r o n m a t r i x have b e e n s t u d i e d e x t e n s i v e l y . P a r a m e t e r s included have been the t e m p e r a t u r e r a n g e s of o c c u r r e n c e of various minor phases, their crystal structures, m o r p h o l o g i e s , t h e i r c o h e r e n c y r e l a t i o n s h i p s with the m a t r i x , and o t h e r p h y s i c a l c h a r a c t e r i s t i c s . Howe v e r , tile d e t e r m i n a t i o n of t h e i r e x a c t c h e m i c a l a n a l y s i s has a t t r a c t e d l i t t l e a t t e n t i o n until r e c e n t l y . 1 It was t h e r e f o r e a m a j o r p u r p o s e of t h i s i n v e s t i g a t i o n to c h e m i c a l l y a n a l y z e the v a r i o u s p h a s e s o c c u r r i n g in the m i c r o s t r u e t u r e of a t y p i c a l v a c u u m m e l t e d n i c k e l i r o n b a s e s u p e r a l l o y . INCO 901 was chosen f o r the study b e c a u s e it is r e p r e s e n t a t i v e of n i c k e l - i r o n b a s e s u p e r a l l o y s with r e l a t i v e l y high c o n c e n t r a t i o n s of c h r o m i u m , m o l y b d e n u m , and t i t a n i u m plus m i n o r e l e m e n t s . T h i s g r a d e of s u p e r a l l o y h a s b e e n c o m m e r c i a l l y p r o d u c e d , often by v a c u u m m e l t i n g , for many y e a r s . It i s f o r g e a b l e , heat t r e a t a b l e , and w e l d a b l e , with good s t r e n g t h and o x i d a t i o n r e s i s t a n c e at t e m p e r a t u r e s up to 760~ (1400~ Its m a j o r u s e i s in j e t engine w h e e l s and d i s k s . A s t a n d a r d c o m m e r c i a l p r a c t i c e f o r p r o d u c i n g such s u p e r a l l o y s r e q u i r e s m e l t i n g and c a s t i n g under p a r t i a l v a c u u m . L i t t l e if any s l a g r e f i n i n g can be a c c o m p l i s h e d in the v a c u u m m e l t i n g p r o c e s s b e c a u s e of the bubbling a n d f r o t h i n g of the s l a g which l e a d s to s e r i o u s c o n t a m i n a t i o n of the v a c u u m s y s t e m . Yet it is often d e s i r a b l e to b e a b l e to r e m o v e s u l f u r , oxygen, and o t h e r unwanted e l e m e n t s d u r i n g the v a c u u m m e l t i n g s t a g e . T h i s c a p a b i l i t y would allow b e t t e r c o m p o s i t i o n c o n t r o l of the m e l t and would a v o i d the need to u s e expensive, high-purity charge materials. Certain r a r e e a r t h e l e m e n t s a r e e f f e c t i v e in d e s u l f u r i z i n g and d e o x i d i z i n g b e c a u s e of t h e i r v e r y l a r g e n e g a t i v e f r e e e n e r g i e s of f o r m a t i o n of the r e s p e c t i v e c o m pounds, e,3 C e r i u m i s the m o s t f r e q u e n t l y added r a r e e a r t h e l e m e n t f o r this p u r p o s e , b e c a u s e it h a s the l a r g e s t n e g a t i v e f r e
Data Loading...
