Fatigue crack propagation in Hastelloy X weld metal · 2017. 2. 3. · in Hastelloy X Weld Metal ....
Transcript of Fatigue crack propagation in Hastelloy X weld metal · 2017. 2. 3. · in Hastelloy X Weld Metal ....
d OAK * ~
RIDGE NATIONAL LABORATORY
1 - - UNION 1 CARBIDE L
d
3 -
OPERATED BY UNION CARBIDE CORPORATIOM
DEPMTNIEIST OF ENERGY FOR M E IlblllTED STATES
ORNUTNl-6999
c
Fatigue Crack Propagation in Hastelloy X Weld Metal
T. Weerasooriya
OAK R I D G E N A T I O N A L L A B O R A T O R Y
. CENTRAL RESEARCH LIBRARY CIRCULATION SECTION .
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ORNL/TM-6999 D i s t r i b u t i o n Category UC-77
Cont rac t No. W-7405-eng-26
METALS AND CERAMICS DIVISION
HTGK BASE TECHNOLOGY PROGRAM
GCR S t r u c t u r a l Materials S tud ie s (01332)
FATIGUE CRACK PROPAGATION I N HASTELLOY X WELD METAL
T. Weerasooriya
Date Published: November 1979
NOTICE This document contains information of a preliminary nature. I t i s subject to revision or correction and therefore does not represent a final report.
OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37830
ope ra t ed by U N I O N CARBIDE CORPORATION
U.S. DEPARTMENT OF ENERGY f o r the
CONTENTS
ABSTRACT e e 1
INTRODUCTION e , . . . 1
MATERIAL CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . 2
Variables Governing Weldment Properties . . . . . . . . . . . 3
Material . . . . . . . . . . . . . . . . . . . . . . . 3
Joint design . . . . . . . . . . . . . . . . . . . . . 5
Welding process and welding parameters . . . . . . . . 5
Postweld heat treatment . . . . . . . . . . . . . . . . 5
Soundness of the welds . . . . . . . . . . . . . . . . 5
Experimental procedure . . . . . . . . . . . . . . . . 6
RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . 10
CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . 21
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FATIGUE CRACK PROPAGATION I N HASTELLOY X WELD METAL
T. Weerasooriya
ABSTRACT
The f a t i g u e crack growth rate of Has te l loy X weld metal increased with stress i n t e n s i t y , temperature , and inve r se f r e - quency. The r e s u l t s were c o r r e l a t e d wi th t h e equat ion
da dN - = ( A K ) ~ ,
f o r cons tan t frequency o r cons tan t temperature. The values of A and n were computed with a l i n e a r regress ion algori thm. With decreas ing frequency a t cons tan t AK and cons tan t t e m - p e r a t u r e (538OC) f a t i g u e crack growth rates approach an upper l i m i t . Fa t igue crack growth rate of t h e weld metal was lower than t h a t repor ted f o r base metal a t 538°C and lower a t 649°C f o r a frequency of 1 Hz.
INTRODUCTION
Has te l loy X , a Ni-Cr-Fe-Mo a l l o y (nominally 47, 23, 19, and 9 w t %,
r e s p e c t i v e l y ) , has been used success fu l ly f o r more than two decades i n
e levated-temperature a p p l i c a t i o n s r equ i r ing both oxida t ion r e s i s t a n c e
and high s t r eng th . It i s e s s e n t i a l l y a single-phase a l l o y with face-
centered cubic s t r u c t u r e . Strengthening is p r imar i ly by so l id - so lu t ion
a l l o y i n g wi th t h e elements chromium, molybdenum, and tungsten. However,
p r e c i p i t a t i o n of ca rb ide particles can a d d i t i o n a l l y s t rengthen t h i s
a l l o y .
I n t h e design of steam- and d i rec t -cyc le (gas t u r b i n e ) High-
Temperature Gas-Cooled Reactors (HTGRs), Has te l loy X has been suggested
f o r f a b r i c a t i o n of duc ts t h a t connect t h e r e a c t o r core t o t h e steam
genera tor o r gas t u r b i n e sec t ion . Also, t he a l l o y has been recommended
f o r thermal b a r r i e r cover p l a t e s surrounding t h e r e a c t o r core.
nominal design temperature f o r ho t duc ts , which c a r r y helium from t h e
The
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2
r e a c t o r core t o the steam genera tor s e c t i o n , i s 788"C, with t h e possi-
b i l i t y of random short- term v a r i a t i o n s of temperature up t o 827OC. The
des ign nominal temperature of t h e hot gas i n t h e i n l e t of t h e ho t duc ts
f o r gas tu rb ine cycle HTGR i s 816°C.192 Has te l loy X i s a l s o one of t he
candida te materials f o r components of gas-cooled-reactor process hea t
p l an t s . I n these systems Has te l loy X could be used f o r duc t ing o r f o r
t h e tube o r suppor t -p la te material of t he in t e rmed ia t e and process hea t
exchangers. 9
I n the above a p p l i c a t i o n s f a b r i c a t i o n procedures r e q u i r e welding i n
t h e cons t ruc t ion of components, and t h e p r o p e r t i e s of t he weldment could
poss ib ly d i f f e r from those of t h e base metal. F a i l u r e s i n weldments are
o f t e n a t t r i b u t e d t o the growth of p r e e x i s t i n g flaws from f a t i g u e of
t h e s e components. I f one knows the rate of growth of s u b c r i t i c a l
c r acks , t h e p r e d i c t i o n of t h e l i f e of components conta in ing f laws is
poss ib le . This approach is p a r t i c u l a r l y u s e f u l f o r design and s a f e t y
a n a l y s i s .
This document provides s u b c r i t i c a l crack growth da ta on Has te l loy X
weld'metal. Test samples were obta ined from weldments t h a t were f a b r i -
ca t ed by welding two Has te l loy X p l a t e s wi th Has te l loy X f i , l l e r metal.
MATERIAL CHARACTERIZATION
Specimens f o r t h i s s tudy were f a b r i c a t e d from solut ion-annealed
12.5-mm-thick Has te l loy X p l a t e s (hea t 2600-4-4284) purchased from
Cabot -Ste l l i t e . The mechanical p r o p e r t i e s of t h i s hea t are:
Heat t reatment solut ion-annealed a t 1177°C fol lowed by r ap id coo l
U l t i m a t e tensi le s t r e n g t h , MPa 790
0.2% y i e l d s t r e n g t h , MPa 345
Elongat ion i n 25 mm, % 49
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The chemical composition of the Hastelloy X plates is:
El emen t Content, wt % Element Content, wt %
Ni Balance co 2.40
Cr 21.79 Mn 0.59 W 0.63 Mo 8.82
Fe 19.06 P 0.018 C 0.06 S C0.005
Si 0.35 B <0.002
Details of weldment fabrication are discussed later in this report.
Figure 1 shows microstructures of the weldment. Second-phase micro-
constituents are probably carbides of the QC type with a lattice
constant of 10.995 (ref. 3). In areas close to the fusion line, Hastelloy X base metal has a larger concentration of these coarse car- bides [Fig. l(b)l.
Variables Governing Weldment Properties
Data obtained from one weldment may differ from the data obtained
from another weldment for several reasons.
Material
Chemical composition can influence the elevated-temperature proper-
ties of a ~eldment.~,5
dictates the composition of the weld metal, base metal dilution, fluxes, and cover gas all contribute to the final deposit composition. In this
study chemical composition of the weld metal (heat 2600-4-4345) with 1.56-mm-diam Hastelloy X wire for filler is:
Although the filler metal composition nominally
Element Content, wt % Element Content, wt %
Cr 21.92 Ni Balance
W 0.42 Mn 0.70
Fe 18.81 Mo 8.85
C 0.08 P 0.022
Si 0.40 S < 0.005
co 2.09
4
a,
D
a a,
4
(d
a, 3 2
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J o i n t design
The geometry of t h e j o i n t can l ead t o d i f f e r e n t r e s i d u a l stress
p a t t e r n s , s t r u c t u r e s , and p r o p e r t i e s of t h e welds. Weldments were
f a b r i c a t e d wi th a V-groove of 75" included angle.
Welding process and welding parameters
The gas tungsten-arc (GTA), gas metal-arc (GMA), sh i e lded metal-arc
(SMA), and submerged-arc (SA) welding processes are most commonly used
i n jo in ing nuc lear power components. These processes can produce welds
wi th d i f f e r e n t m e t a l l u r g i c a l s t r u c t u r e and p rope r t i e s . Even wi th a
g iven process , v a r i a t i o n i n welding parameters and techniques , such as
c u r r e n t , vo l t age , t r a v e l speed, e l e c t r o d e s i z e , number and sequence of
pas ses , amplitude, frequency, p o l a r i t y , and shape of app l i ed vo l t age ,
may l ead t o d i f f e r e n t p r o p e r t i e s of t h e weldments . , Weldments were made with the fol lowing parameters:
Welding process GTA
Speed 3.75 x lo4 mm/s (625 mm/min)
Voltage 9-9.5 v Passes 7
Current 195 A
S t r a i g h t p o l a r i t y
Elec t rode 2.34 mm i n diameter , 30" inc luded angle
Postweld hea t t rea tment
Welds in nuclear a p p l i c a t i o n s are hea t - t r ea t ed many t i m e s t o a l t e r
m e t a l l u r g i c a l s t r u c t u r e o r t o r e l i e v e r e s i d u a l stresses. However, t h e
weldment t h a t was f a b r i c a t e d f o r t e s t i n g i n t h i s program w a s no t post-
weld hea t - t rea ted .
Soundness of t h e welds
Defec ts , such as i n c l u s i o n s , po ros i ty , and incomplete fus ion , can
degrade t h e p rope r t i e s . The weldment was radiographed, and no d e f e c t s
were indica ted .
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Experimental procedure
Standard (ASTM E 6 4 7 ) compact t ens ion (CT) specimens were prepared
from weldments t h a t were f a b r i c a t e d as o u t l i n e d above. The dimensions
of t h e specimens’are given i n Fig. 2. The notched area of t h e specimen
w a s l o c a t e d a t t h e c e n t e r of t h e weld metal such t h a t t h e major a x i s of
t h e weldment coincided with the major a x i s of t he notch. The base metal
w a s o r i e n t e d such t h a t t h e r o l l i n g d i r e c t i o n w a s perpendicular t o t h e
plane of crack gro,wth.
ORNL-DWG 79- 10401
HASTELLOY X
HASTELLOY X
Fig. 2. Dimensions i n Millimeters of t he Compact Tension (CT) Specimen with the Weldment.
Specimens were precracked a t room temperature with a servo-
h y d r a u l i c t e s t i n g machine. Precracking w a s performed wi th a s i n o s o i d a l
waveform and was terminated when a value f o r maximum stress i n t e n s i t y
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(&ax) s l i g h t l y smaller than the i n i t i a l Kma, f o r t h e tests w a s reached.
The r a t i o ( R ) of Kmin t o K,,, w a s kept a t 0.05 throughout a l l t h e tests.
The machine se tup used f o r elevated-temperature f a t i g u e growth
t e s t i n g is shown i n Figs. 3 and 4.
closed-loop, servo-control led e l e c t r o h y d r a u l i c MTS t e s t i n g machine,
employing a t r i a n g u l a r waveform. The tests were conducted i n a i r wi th
a stress r a t i o value (Pmin/Pmax) of R = 0.05 (according t o ASTM E 647,
u n l e s s s t a t e d otherwise) . Induct ion hea t ing maintained t h e e l eva ted
temperature during f a t i g u e t e s t i n g . Specimen temperature w a s c o n t r o l l e d
t o 4l0C, while t h e temperature v a r i a t i o n along t h e path of t h e crack w a s
less than 6'C. Crack l eng ths were measured o p t i c a l l y wi th t r a v e l i n g
microscopes a t p e r i o d i c i n t e r v a l s .
A l l tests were conducted on a
Crack growth rates were computed by f i t t i n g a continuous cubic
s p l i n e curve t o t h e average crack l eng th dataO7 The c loseness of t h e
.I-
- i n
Fig. 3. The Tes t ing Machine. Induct ion h e a t i n g was used t o main- t a i n temperature.
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Fig. 4. Close-up of Heating Coil in Testing Machine.
fitted cubic spline curve to the experimental points was determined by
the variable S in Eq. (1):
N
i=1 [ai - ai(fit)12 = S2N , (1)
where
ai = measured crack length, and
ai(fit) = fitted crack length.
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The s p l i n e curve w a s f i t t e d t o s a t i s f y t h e above equation.
y s i s S w a s taken as 0.025 mm and can be considered as a measure of t he
confidence of t he o p t i c a l readings. The stress i n t e n s i t y expression
used t o c a l c u l a t e LW was as fol lows:
I n t h i s anal-
0 . 5 1 . 5 2 . 5 AK = jqj-j[ 29 a 6 (i) - - 185.5(;) + 655.7(;)
- 1017(;) 3 . 5 + 638.9(;)4*5] ,
where
AI’ = cycl ic load range ( i .e . , Pmax - Pmin),
a = crack l eng th ,
B = specimen th i ckness , and
W = specimen width.
The tests were terminated a t t h e onset of permanent crack opening.
A computer code w a s prepared and used t o c a l c u l a t e growth rates and
p l o t growth vs A K , as discussed above.
least squares r eg res s ion l i n e f o r daldN vs AK p l o t s and c a l c u l a t e A and
n i n t h e equat ion
The computer code w i l l f i t a
where - - $ - crack growth i n mm/cycle, and
AK = stress i n t e n s i t y i n MPafifor each p l o t .
We conducted tests t o f i n d t h e v a r i a t i o n of s u b c r i t i c a l crack
growth rates with varying temperatures a t 1 Hz. Tests were conducted a t
538, 650, and 760°C. Also, tests were conducted t o f i n d t h e behavior of
c r ack growth rates with f r equenc ie s of 0.1, 1 , and 10 Hz a t 538°C.
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RESULTS AND DISCUSSION
We c o r r e l a t e d crack growth da ta wi th Eq. (3) . Figures 5 through 7
g i v e the daldN vs AK da t a on loga r i thmic coord ina te s f o r t h e tests con-
ducted t o f i n d out t h e e f f e c t of temperature on f a t i g u e crack growth
rates f o r a cons t an t frequency. These f i g u r e s a l s o g ive both t h e l i n e a r
r e g r e s s i o n l i n e s f o r t h e s e d a t a and t h e values of A and n i n Eq. ( 3 )
(daldN - mmlcycle; AK - MPafi) f o r t h e r eg res s ion l i n e s .
band f o r weld metal i s on t h e o rde r of p l u s o r minus twice t h e p red ic t ed
va lues by t h e r eg res s ion l i n e . This probably r e s u l t e d from t h e ani-
so t ropy and inhomogeniety of t h e weld metal. Figure 8 g ives a com-
pa r i son of t h e v a r i a t i o n of f a t i g u e crack growth rate wi th temperature
a t 1 Hz. A s observed f o r most of t h e materials, crack growth ra te
i n c r e a s e s wi th i n c r e a s i n g temperature f o r Has te l loy X weld metal. One
exp lana t ion is t h a t as temperature i n c r e a s e s d e t e r i o r a t i o n of t h e crack
t i p from ox ida t ion i s higher. However, a t higher stress i n t e n s i t i e s
d i f f e r e n c e s i n crack growth rates from temperature become smaller. A t
h i g h e r growth rates unoxidized metal i s r a p i d l y exposed, and hence oxi-
d a t i o n a t t h e crack t i p has l i t t l e e f f e c t on growth rate. F igu res 5 and
6 compare t h e f a t i g u e crack growth rates of weld metal and base metal.
A t both 538 and 650°C base metal has a higher crack growth ra te compared
t o t h a t of weld metal.
growth rates of base m e t a l and weld metal i n c r e a s e s w i t h i n c r e a s i n g
stress i n t e n s i t y f a c t o r .
The s c a t t e r
A t 650°C t h e d i f f e r e n c e of t h e f a t i g u e crack
Figures 9 and 10 g i v e t h e f a t i g u e crack growth ra te d a t a , f i t t e d
r e g r e s s i o n l i n e , and values of A and n f o r f u r t h e r tests conducted on
weld m e t a l t o f i n d t h e e f f e c t of frequency on f a t i g u e crack growth rates
a t 538°C.
growth rate of weld metal a t 538OC.
growth rate i n c r e a s e s with decreasing frequency. I n t h e range of f r e -
quencies between 0.1 and 1 Hz, t h e d i f f e r e n c e i n t h e f a t i g u e crack
growth rate (FCGR) is not s u b s t a n t i a l , but t h e d i f f e r e n c e i n crack
growth rates between t h e f r equenc ie s of 10 and 0.1 Hz o r 10 and 1 Hz is
g r e a t e r .
Figure 11 compares t h e e f f e c t of frequency on f a t i g u e crack
In gene ra l , t h e f a t i g u e crack
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ORNL-DWG 78-18702R
D K . STRESS INTENSITY FACTOR ( K s i f i . 1
to 20 30 40 50 60 70 80 10-2
ENVIRONMENT : AIR 1 0 - ~
t 0-3
1 0 - ~
10-6
W -I V t V \ E E Y
W l- a a I I-
g a W Y V a a V
i 0 \ 0 0
4 o - ~
- - HASTELLOY X
WELD METAL-
A K . STRESS INTENSITY FACTOR ( M P o f i )
W I- a. a I I-
g a W
Y V
V
a a
i U \ 0 0
Fig. 5. Fa t igue Crack Growth Rate of Has te l loy X Weld Metal a t 538OC and 1 Hz. Base metal data is from: C. R. Brinkman e t a l . , Application of Hastetzoy X in Gas-Cooled Reactor Systems, ORNL/TM-5405 (October 1976). Note t h a t S I u n i t s were employed i n t h e development of t h e above equat ion.
1 2
ORNL- DWG 78- 22316R
10-2
10-3
W -J V t V \ E E Y
I I-
Lz a
i \o 'p
10-5
A K , STRESS INTENSITY FACTOR ( K s i f i . 1
10 20 30 40 50 60 70 80
I ' I ' I I I I I ' I ' I 'I I
I I I I ' I l l
TEMPERATURE = 649 4: I 0 I l l FREQUENCY = 1 Hz I O I I I
IRONMENT : AIR 10-7.77 ( ~ ~ ) 3 . 0 0
I 1 I I 0
WELDED SPECIMEN ORIENTATION
0
L: HASTELLOY X t WELD METAL '-...--
1 0 - ~
W
t a
Y V Q CL V
10-6 i \o U
10-6 I O ' 20 40 60 00 I O 2
OK. STRESS INTENSITY FACTOR (MPo ./& 1
Fig. 6. F a t i g u e Crack Growth Rate of Has te l loy X Weld Metal a t 649°C and 1 Hz. Base metal d a t a is from: C. R. Brinkman et a l . , Application of Hastelloy X i n Gas-Cooled Reactor Systems, ORNL/TM-5405 (October 1976).
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ORNL-DWG 78-22317
AK, STRESS INTENSITY FACTOR ( k s i f i . ) 10 2 0 30 40 50 60 70 00
AK. STRESS INTENSITY FACTOR ( M P o f i )
Fig. 7. Fa t igue Crack Growth Rate of Has te l loy X Weld Metal a t 760°C and 1 Hz.
14
ORNL-DWG 78-22318
AK, STRESS INTENSITY FACTOR (Ks i&)
40 20 30 40 50 60 70 00 40-2
1 0 - ~
- LL' -I V * V
W J V t V \
E E 10-5 2 t !3 a
I t ~ - ~ I-
2
- W
W
a I
I-
a (3
Y V
V
a L 3
Y V U a V
a a
\o \
2 to-6 g 0
0 D
4 o - ~
WELD METAL
t 0-7
10-6 40' 20 40 60 80 402
P K . STRESS INTENSITY FACTOR ( M P a f i )
Fig. 8. E f f e c t of Temperature on Fa t igue Crack Growth Rate of Has te l loy X Weld Metal a t 1 Hz.
15
W J
V \ Y E E -
I c
i 0 \ 0 0
20 40 60 00 102 AK, STRESS INTENSITY FACTOR (MPo 6)
Fig. 9. 538°C and 0.1
Fa t igue Crack Growth Rate of Has te l loy X Weld Hz . Metal a t
16
10-2
E -
ORNL-DWG 79-9898
AK, STPESS INTENSITY FACTOR ( K s i f i 1 10 20 30 40 50 60 70 00
TEMPERATURE = 538°C
VIRONMENT : AIR
1 0 - ~
-
I c
20 4 0 60 80 102 AK. STRESS INTENSITY FACTOR ( MPa f i )
Fig. 10. Fa t igue Crack Growth Rate of Has te l loy X Weld Metal a t 538OC and 10 Hz.
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ORNL-DWG 79 - 9250
W
Lz 5 I I-
a (3
Y V
m V
a
A K . STRESS INTENSITY FACTOR ( K s i f i )
10 20 30 40 50 60 70 80 10-2
10-3
IO -4
A K . STRESS INTENSITY FACTOR ( MPo 6)
1 o - ~
IO-^
Y
Fig. 11. E f f e c t of Frequency on Fa t igue Crack Growth Rate of Has te l loy X Weld Metal a t 538°C.
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The p r i n c i p a l causes of t h e e f f e c t of frequency are aga in bel ieved
t o be: ( 1 ) t h e increased ox ida t ion a t t h e crack t i p , and ( 2 ) t h e t ran-
s i e n t creep t h a t occurs during the longer cyc le per iods a t t h e lower
f requencies . There a p p e a r s t o be an upper l i m i t of c rack growth rate
f o r decreas ing frequency. When t h e frequency i s reduced t h e r e may be a
s t a g e a t which increased environmental a t t a c k is balanced by t h e
b lun t ing and stress r e l a x a t i o n a t t h e crack t i p and hence a reduct ion of
t h e d r iv ing f o r c e aK a t the crack t i p . Figure 12 shows r e p r e s e n t a t i v e
areas of t h e f r a c t u r e sur face . These c l e a r l y show t h e fat igue-induced
s t r i a t i o n s on t h e crack s u r f a c e and how these s t r i a t i o n conf igu ra t ions
seem t o d i f f e r . This i s expected as weld metal does not have a homo-
geneous s t r u c t u r e ( a s a r e s u l t of mul t ipass welding, i nc lud ing o s c i l -
l a t i o n i n any given pass) .
Figure 13 shows a t y p i c a l o r i e n t a t i o n of the f a t i g u e crack wi th
r e s p e c t t o t h e mic ros t ruc tu re of t he weld metal. Cor re l a t ion of crack
conf igu ra t ion and mic ros t ruc tu ra l d e t a i l s w a s no t de t ec t ed , though on a
few occasions t h e crack tends t o change d i r e c t i o n t o make t h e d e n d r i t e s
p a r a l l e l i n the s t r u c t u r e .
CONCLUSIONS
This r epor t p re sen t s the r e s u l t s of p a r t of a broad program of
s tudy on FCGR p r o p e r t i e s f o r HTGR a p p l i c a t i o n s . We discussed r e s u l t s of
t h e c h a r a c t e r i z a t i o n of f a t i g u e crack growth i n a i r f o r Has te l loy X weld
metal. We concluded t h e fo l lowing from the r e s u l t s :
1 . The FCGR i n weld metal i nc reases wi th inc reas ing temperature a t
1 Hz i n t h e range 538 t o 760°C.
2. The FCGR f o r weld metal decreases wi th inc reas ing frequency
from 1 t o 10 Hz a t 538°C. Also, t h e r e i s an upper l i m i t growth rate f o r
decreas ing frequency a t a cons tan t AK value.
3. The FCGR of base metal i s h igher than that of weld metal both
a t 538 and 649°C f o r frequency of 1 Hz.
19 d
03 c
r"
5
0
a( c
I
0
CT c3 Y
O
5 "t LL 0
Z 0
I- O W
CT
-
-
n
20
DIRECTION OF WELDING -
Fig. 13. Orientation of Two Locations of a Typical Fatigue Crack with Respect to the Microstructure.
2 1
ACKNOWLEDGMENTS
. The au tho r g r a t e f u l l y appreciates t h e h e l p and pa t i ence shown by
J. P. S t r i z a k dur ing t h e i n i t i a t i o n pe r iod of t h i s t e s t i n g program.
The r e p o r t was reviewed by M. K. Booker and R. W. Swindeman, e d i t e d
by B. G. Ashdown, and prepared f o r f i n a l p u b l i c a t i o n by P. T. Thornton.
REFERENCES
1. P. L. Ri t tenhouse , Initial Assessment of the Status of HTGR Metallic
Structural Materials Technology, ORNL/TM-4760 (December 1974).
2. C. R. Brinkman e t a l . , Application of Hastelloy X in Gas-Cooled Reactor Systems, ORNL/TM-5405 (October 1976).
3. G. Y. L a i , "An I n v e s t i g a t i o n of t h e Thermal S t a b i l i t y of a
Commercial Ni-Cr-Fle-Mo Alloy (Has te l loy X ) , " Metall. Trans. A 9A:
827-33 (1978).
4. R e T. King, D. A. Canonico, and C. R. Brinkman, "Elevated-
Temperature Weldment Behavior as Rela ted t o Nuclear Design
Criteria," Weld. J. (Miami) 54(8): 265-s-275-s (August 1975).
5. F. C. Hul l , "The E f f e c t of Composition on t h e Stress-Rupture
P r o p e r t i e s of F u l l y A u s t e n i t i c S t a i n l e s s S t e e l Weld," paper pre-
s e n t e d a t F i r s t Na t iona l Congress on P res su re Vessels and Pip ing ,
San F ranc i sco , C a l i f . , May 10-12, 1971.
6. G. M. Goodwin, N. C. Cole, and G. M. S l augh te r , "A Study of Ferri te
Morphology i n A u s t e n i t i c S t a i n l e s s Steel Weldments," Wetd. J. (Mhni) 51(9): 425-s-429-s (September 1972).
T. Weerasooriya, Fatigue Crack Propagation in the Heat-Affected Zone of 2 1 / 4 Cr-1 Mo Steel and ERNiCr-3 Weldments -Interim Report, ORNL/TM-6971 ( i n p r e s s ) .
7.
I
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