The effect of forging history on the strength and microstructure of TDNiCr (Ni-20Cr-2ThO 2 )
- PDF / 1,933,100 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 99 Downloads / 151 Views
in. (3.8 cm) t h i c k u p s e t f o r g e d p r e f o r m s . The p r e f o r m and b a r m a t e r i a l s w e r e both p r e p a r e d f r o m b l e n d e d p o w d e r s and c o n s o l i d a t e d by i s o s t a t i c p r e s s i n g , h y d r o gen s i n t e r i n g , and f a b r i c a t i o n . T y p i c a l c h e m i c a l a n a l y s i s i s g i v e n in T a b l e I. G r a i n s i z e and e l e v a t e d t e m p e r a t u r e s t r e n g t h d a t a a r e s u m m a r i z e d for the e x p e r i m e n t a l m a t e r i a l s in T a b l e II. A 2 ;~m g r a i n s i z e and 2000~ (1366 K) t e n s i l e s t r e n g t h of 3 k s i (21 M N / m 2) w e r e t y p i c a l of the a s - r e c e i v e d m a t e r i a l s . High t e m p e r a t u r e h e a t t r e a t m e n t a t 2450~ (1616 K ) - t h e a l l o y m e l t s a t ~ 2 5 5 0 ~ (1672 K ) - h a d no e f f e c t on the s t r e n g t h o r g r a i n s i z e of the p r e f o r m m a t e r i a l , but i n c r e a s e d the g r a i n s i z e of t h e e x t r u d e d b a r to 2000 ~tm and i t s 2000~ (1366 K) t e n s i l e s t r e n g t h to 18.9 k s i (131 MN/m2). T h i s p r o n o u n c e d d i f f e r e n c e in heat t r e a t r e s p o n s e e x e m p l i f i e s the s t r o n g i n f l u e n c e that p r i o r t h e r m o m e c h a n i c a l h i s t o r y can have on t h e p r o p e r t i e s of T D N i C r . P r o c e s s i n g of both m a t e r i a l s w a s s i m i l a r up to the p o i n t of f a b r i c a t i o n . The p r e f o r m m a t e r i a l w a s f a b r i c a t e d by s i m p l e u p s e t f o r g ing at 1850~ (1283 K) t h r o u g h a 6 to 1 r e d u c t i o n f o l lowed by a n n e a l i n g at 2000~ (1366 K). The b a r s t o c k w a s f a b r i c a t e d by e x t r u s i o n , a m o r e u n i d i r e c t i o n a l p r o c e s s , and g i v e n a 16 to 1 r e d u c t i o n at 1900~ (1311 K) without a n y s u b s e q u e n t a n n e a l . L a r g e u n i d i r e c t i o n a l r e d u c t i o n s have b e e n c o m m o n l y a s s o c i a t e d with i m p r o v e d p r o p e r t i e s in d i s p e r s i o n s t r e n g t h e n e d m a t e rials,i-s,a
Table I. Chemical Analysis Typical of the Experimental Materials
AlloyingConstituents,Wt Pet Cr ThO2 Ni 20-21
2.1-2.6
Balance
C 350
AnalyzedContaminants,ppm N S Cu Co 100
40
50
200
Table II. Grain Size and Strength Typical of the Experimental Materials
Materials
Grain Sizeand TensileStrengthat 2000~ (1366 K) As-Received Condition Annealed1h/2450~ (1616 K)
PreformMaterial Extruded Bar
2 #m, 3 ksi (21 MN/m ~) 2 tam,3 ksi (21 MN/m2) 2 tam,3 ksi (21 MN/m~) 2000tam, 18.9 ksi (131 MN/m~) VOLUME 6A, DECEMBER 1975-2171
(977)
PUNCH
(lO89)
1300 I
(v2oo)
1700 f AsAnnealedat 22 Forged 2450~ (1616K) Preform I Forged 85% --'0"+ 20 -Mat'l. ~Forged60% --~)..24
1500 I
18
160 140
9 - 120
..~ 16
/ ~
14 --
I. 5"
-- I ~
(3.8 cm)
Fig. 1--A schematic representation of channel die forging. This tooling was used to forge the starting materials into test plates measuring 12 in. • 1.5 in. • 0.15 in.
Data Loading...
