The stress corrosion resistance and fatigue crack growth rate of a high strength martensitic stainless steel, AFC 77
- PDF / 1,767,759 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 74 Downloads / 176 Views
Mechanical Testing The t e c h n i q u e s used to d e t e r m i n e f r a c t u r e toughness and t e n s i l e p r o p e r t i e s were fully d e s c r i b e d in a r e c e n t p u b l i c a t i o n I and will not be r e p e a t e d h e r e . S t r e s s c o r r o s i o n t e s t i n g under p l a n e - s t r a i n condit i o n s was c a r r i e d out on fatigue p r e c r a c k e d Charpy and p r e c r a c k e d s i n g l e - e d g e notch bend s p e c i m e n s (7.5 by 1.5 by 0.48 in.) t e s t e d in c a n t i l e v e r bending. 2 It should be noted that for the t e m p e r e d 500~ condition the s p e c i m e n t h i c k n e s s falls below the r e q u i r e m e n t s of the ASTM Standards for f r a c t u r e t o u g h n e s s t e s t i n g , a l though no s t a n d a r d s have yet been s e t for s t r e s s c o r r o s i o n t e s t i n g . T e s t i n g was c a r r i e d out in a 3.5 pct s a l t s o l u t i o n (sodium chloride) with f r e s h s o l u t i o n cons t a n t l y d r i p p i n g into the upturned notch. The c r a c k was i m m e r s e d in the s a l t s o l u t i o n before the load was applied. Specimens w e r e held 1 week at each s t r e s s i n t e n s i t y l e v e l b e f o r e unloading. If c r a c k growth was l e s s than 0.1 in., the s p e c i m e n was again fatigue c r a c k e d and r e t e s t e d at a d i f f e r e n t s t r e s s i n t e n s i t y l e v e l . The extent of s t r e s s c o r r o s i o n growth at each s t r e s s i n t e n s i t y l e v e l could e a s i l y be s e e n between the two fatigue c r a c k s . The p l a n e - s t r a i n s t r e s s c o r r o s i o n t h r e s h o l d KIsec is the h i g h e s t s t r e s s i n t e n s i t y l e v e l that could be m a i n t a i n e d without c r a c k growth. The growth r a t e of the s t r e s s c o r r o s i o n c r a c k was c a l c u l a t e d by d i v i d i n g the c r a c k length by the total t i m e at that p a r t i c u l a r s t r e s s i n t e n s i t y level. Since the i n cubation p e r i o d is i g n o r e d , the r a t e of c r a c k growth is plotted as an a p p a r e n t c r a c k growth r a t e . This plotting method does not change the KIsec value, b e c a u s e the c r a c k growth r a t e is z e r o at the t h r e s h o l d . After a s p e c i m e n had b r o k e n in s t r e s s c o r r o s i o n , a value KI5 was c a l c u l a t e d u s i n g the total c r a c k length (including the length of c r a c k that had grown in s t r e s s
Table I. Chemical Composition, Weight Percent
Heat C Si Mn S P Ni Cr Mo V Co N No. 64555 0.16 0.13 0.18 0.021 0.015 0.21 14.0 5.02 0.23 13.41 0.04 VOLUME 1, OCTOBER 1970-2919
800 ~ F TEMPER 500 ~ F TEMPER
>..
7000 F TEMPER
>-
150
KI6
>100
-
I -
9 ~o -J o3 u.i
1001-KI-~
i
= >
(z:: LU ~
I 10
00L-~ ~
-~
l
~
100
~
100
-
KI.~
i ' - KZ~T
I 100
0
--
I
I
i
1
10
100
APPARENTCRACKGROWTH
RATE (IN. X 10.3 PER HR)
RATE (IN. X 10.3 PER HR)
APPARENT CRACK GROWTH RATE (IN. X 10-3 PER HR)
(b)
(c)
900~ F TEMPER
1100o F TEMPER
>
~F
IZ
Kic
Data Loading...
