Effect of hot work on the properties of Waspaloy
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A. A. PINKOWISH,
W. P. DANESI,
J. F. RADAVICH,
AND
W. H. COUTS
The effects of p r o c e s s h i s t o r y on the p r o p e r t i e s and m i c r o s t r u c t u r e of wrought Waspaloy have b e e n investigated. F o r g e p r a c t i c e is shown to be c r i t i c a l if the f o r g i n g t e m p e r a t u r e e x c e e d s the ~' solution t e m p e r a t u r e . A light r e d u c t i o n at high t e m p e r a t u r e s d e c r e a s e s f r a c t u r e d u c t i l i t y as evaluated by i m p a c t , t e n s i l e and r u p t u r e t e s t s . The m o s t s i g n i f i c a n t m i c r o s t r u c t u r a l f e a t u r e i s the f o r m a t i o n of MC c a r b i d e b o u n d a r y f i l m s . W A S P A L O Y is a wrought n i c k e l - b a s e s u p e r a l l o y often s e l e c t e d for l o n g - t i m e s e r v i c e a p p l i c a t i o n s in gas t u r b i n e s . Although the c o m p o s i t i o n and heat t r e a t m e n t of a wrought s u p e r a l l o y a r e u s u a l l y specified, p r o c e s s h i s t o r y i s n o r m a l l y not defined except for the i n d i r e c t guide of g r a i n size l i m i t s . B e c a u s e a wide r a n g e of def o r m a t i o n conditions is p o s s i b l e l-a it was the p u r p o s e of this study to e s t a b l i s h the effect of some of the m o s t c o m m o n p r o c e s s i n g v a r i a b l e s upon the p r o p e r t i e s and m i c r o s t r u c t u r e of Waspaloy heat t r e a t e d for m a x i m u m c r e e p r e s i s t a n c e , i.e., as for t u r b i n e b l a d e s . E X P E R I M E N T A L PROCEDURE
Hot r o l l e d b a r of 12~ in. d i a m was obtained for m a x i m u m l o n g i t u d i n a l u n i f o r m i t y . Its c h e m i s t r y was: Mn
Si
S
Fe
0.045
0.02
0.01
0.005
Ti
Mo
Co
2.86
3.96
12.74
Cu 0.06
Cr
A1
18.77
1.37
B
Zr
Ni
0.0074
0.060
Bal.
0.29
The v a r i a b l e s w e r e forge t e m p e r a t u r e and d e f o r m a tion p e r heating. Nine f o r g i n g s w e r e c o m p a r e d ; t h e s e included a l l c o m b i n a t i o n s of t h r e e forge t e m p e r a t u r e s and t h r e e d e f o r m a t i o n c y c l e s . The s e q u e n c e s and t h e i r codes w e r e : Code
Function
T i m e and T e m p e r a t u r e
Solution C a r b i d e Stabilize Age
4 Hr at 1975~ a i r cool 24 Hr at 1550~ a i r cool 16 Hr at 1400~ a i r cool
Metallographic s p e c i m e n s were obtained r e p r e s e n t i n g all s t a g e s of f o r g i n g and heat t r e a t m e n t . Evaluation Techniques
Material History
C
forged within s t a i n l e s s s t e e l pipe of ~ in. wall t h i c k n e s s . Each piece was a i r - c o o l e d between o p e r a t i o n s . After forging o p e r a t i o n s , a s t a n d a r d heat t r e a t m e n t was applied as follows:
Meaning
A
F o r g e d f r o m a f u r n a c e a f t e r 2 h r at 2150~
C
F o r g e d from a f u r n a c e after 2 hr at 1975~
E
F o r g e d f r o m a f u r n a c e a f t e r 2 hr at 1800~
1
T h r e e s u c c e s s i v e d e f o r m a t i o n s , each of 40 p
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