The effects of composition on mechanical properties of W-4Re-Hf-C alloys
- PDF / 1,459,408 Bytes
- 6 Pages / 613 x 788.28 pts Page_size
- 14 Downloads / 204 Views
I N T E R E S T in t u n g s t e n for a e r o s p a c e and n u c l e a r a p p l i c a t i o n s h a s p r o m p t e d i n v e s t i g a t i o n s to i m p r o v e the s t r e n g t h and w o r k a b i l i t y of t h i s h i g h e s t m e l t i n g m e t a l . P r e v i o u s s t u d i e s 1'2 have shown that the h i g h - t e m p e r a t u r e s t r e n g t h of t u n g s t e n can be i n c r e a s e d up to eightfold b y the p r e s e n c e of hafnium c a r b i d e p r e c i p i t a t e s and that l o w - t e m p e r a t u r e d u c t i l i t y could be i m p r o v e d b y m o d e r a t e a d d i t i o n s of r h e n i u m . Subsequently, a d d i t i o n s of 4 at. p c t Re to the W - H f - C a l l o y s w e r e u s e d s u c c e s s f u l l y to i m p r o v e the s t r e n g t h - d u c t i l i t y p r o p e r t i e s of the t e r n a r y a l l o y s . 3'4 The p u r p o s e of t h i s s t u d y of the W - R e - H f - C a l l o y s was to e x a m i n e the ef~ f e c t s of Hf and C in e x c e s s of s t o i c h i o m e t r i c HfC on mechanical properties. The p r e s e n t r e p o r t p r o v i d e s a d d i t i o n a l d a t a on a s w o r k e d W - R e - H f - C a l l o y s and d e s c r i b e s the effect of e x c e s s hafnium and c a r b o n (above that c a l c u l a t e d for s t o i c h i o m e t r i c HfC) on bend, t e n s i l e , and c r e e p p r o p erties. A correlation between carbide particle comp o s i t i o n and high t e m p e r a t u r e c r e e p b e h a v i o r is p r e sented. E X P E R I M E N T A L PROCEDURE Materials The t u n g s t e n a l l o y s u s e d in t h i s s t u d y contained f r o m 3.1 to 4.4 at. p c t r h e n i u m , 0.20 to 0.76 at. p c t hafnium, and 0.01 to 1.35 at. p c t c a r b o n . Oxygen and n i t r o g e n i m p u r i t i e s r a n g e d f r o m 6 to 12 p p m and 1 to 4 ppm, r e s p e c t i v e l y . Mol p e r c e n t HfC was a s s u m e d to be equal to the at. p c t /If o r C, w h i c h e v e r was l o w e r . Hafnium contents w e r e d e t e r m i n e d by an ion exchange and c o l o r o m e t r i c p r o c e d u r e with an e s t i m a t e d p r e c i s i o n of • p c t . C a r b o n d e t e r m i n a t i o n s w e r e m a d e by a c o m b u s t i o n c h r o m a t o g r a p h i c p r o c e d u r e (Leco) and a r e a l s o c o n s i d e r e d to have a p r e c i s i o n of about • 5 pct. The a l l o y m a t e r i a l s w e r e p r e p a r e d b y thorough b l e n d ing of the m e t a l and g r a p h i t e p o w d e r s , h y d r o p r e s s i n g , WALTER R. WITZKE is Research Metallurgist, Lewis Research Center, NASA, Cleveland, Ohio. 44135. Manuscript submitted May 7, 1973.
METALLURGICAL TRANSACTIONS
and s i n t e r i n g into e l e c t r o d e s h a p e s . T h e s e w e r e v a c uum a r c m e l t e d into 5 . 8 - c m (2.3-in.) d i a m ingots weighing about 4500 g (10 lb). B i l l e t s m a c h i n e d f r o m t h e s e ingots w e r e canned in p o w d e r m e t a l l u r g y m o l y b d e n u m and e x t r u d e d at 2200~ (4000~ with a r e duction r a
Data Loading...
