ML20079L428

Forwards Study Re Cracking of Nickel Base Austenitic Alloys Referenced in 840116 Response to Interrogatories Re Steam Generator Repairs

ML20079L428
Person / Time
Site:	Crane
Issue date:	01/19/1984
From:	Aamodt N AAMODTS, JOINT PETITIONERS - TMI
To:	Atomic Safety and Licensing Board Panel, NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD), THREE MILE ISLAND ALERT
References
INTR-840119, NUDOCS 8401260116
Download: ML20079L428 (13)

Text

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.,s U iY:

N ain niao R. D. 5, Box 428 Coatesville, PA 19320'_;j f,qr, jr r.

~.

J a nua ry 19, 1994

. To the Board and Parties:

Dockst 50-269 - Steam Generator Tube Repairs - Three Mile Island, Unit 1

?

Counsel for Licensee informed us today that a study referenced in our response to interrogatories, served January 16, 1984, was not received by them. We provided them with additional identification of this study so that they may have been able to obtain a copy. They agreed to check with Docketing & Service to determine whether the study was left-out.

'It was, therefore, we are providing copies, at this time, to the board and parties, and apologize where there was oversight for any inconvenience this may have caused.

Sincerely yours,

/

/

A. h'bik:d GI

& y{tl t

Norman O. Aamodt for Lee et al., J oint Inten enors l

l h

i l

0 m

v r

G..,./ l o.e-a.4 3 %

w,

. W -~-; [ w s ' '

',;4:., 4 ) 4.$. m

..:h-k

6 -6 AWE

• 9 '

HISTORICAL REVIEW OF THE PRINCIPAL RESEARCH

/ - ~L., L-CONCERNING THE PHENOMENA OF CRACKING OF NICKEL BASE AUSTENITIC ALLOYSW J. Blanchet, H. Coriou. L. Grail,

~-

' ~ ~

C. Mahieu. C. Orur, anc' G. Turluer *

~ - -- "

~ ~ ~ ~ -

~

D In a number of studies, we have shown that austenitic k % g <% r-EE+ W -M:R alloys (nickel-chromium-iron) with high nickel contents (Ni 1.

~

' h, L

777c), such as inconel 600, are susceptible to the o

phenomena of stress corrosio 1. The cracking is essentiaDy

.j interganular and appears in demineralized water, at 300 g

and 350 C,in the absence of oxygen, chlorides, and traces of certain harmfulimpurities (lead),' and et the bottom of

,/.*

j recess zones. It is significant that the period ofincubation 3

r L

4

' (L.,,

-preceeding the appearance of cracks is long (on the order of several months under our experimental conditions). Inconel l.

j?

600 type alloys are often recomr. tended for the construe.

,/ '

tion ofvarious reactor components that undergo stress: steam f

generators and internal structures of high-pressure water g

reactors. We will review some previous results in 1:e first I

5 part of the p3per s

x Tests in Water at 350 C

^{

The nominal compositions of the alloys are as foDows:

. 5 n

4 v.

--n (1) Cr 17%. Ni 10%, (2) Cr 17%, Ni 35%, (3) Cr 175, Ni 45%. (4) Cr 17%, bi 77%,(5) Cr 20%, Ni 45%, Mn 5%, and

.e :

(6) inconel 600.

N a

We have performed experiments with I mm sheet a 'N specimens in the quench annealed condition. The exut I-d.

t compositions of these alloys are given in Table 1.

, i..

'r TAeLE1 FIGURE 1 - Alloy Cr 17%, Ni 77". cracked afte{ six m

_ a -,, %

months of testing in 350 C water.

T,==

C Ce ps, he.

S.

Ti est 5

Po tec ect2 17.i icJ c6 os 00,0 m=

almost always interganularly wish, howeve

_ t=nspanular paths for tne alloy Cr.17%,.h...@..r, a fe im e e:s i t.:

so os u o.oio

'h.e o oi.

17J 44.3 is o.s com m--

i.

.The other x.o a :ae. isJ _.u

.o o.,

-w.

.aco...

=

oce: - is e m -io c.:

se" a~

allov types: Cr 17G. Ni 109: Cr 17%, Ni 35% Cr 17%,Ni -

e ar====

0 0s o is t 78 4 c i2 C.2 oJ4-R e-te.a 45G; and Cr 0' Ni 459. Mn 5G do not show any 6x cra: king whatsceser after 10 months of testing. Other 5

Pu'a Water researchers have also produced stress crackingin inconel These alloys have been tested under the three following 600 in pure water :t hi;h temperatures.

conditions: (1) medium: demineralized and deoxygen:ted it is noted thn cracking as shown in Figure 1 occursin water (0: < 3 ug. kg-');(2) temperature: 350 C.and (3)

n alloy whose composition is similar to th:t of Inconel sir:s3 pplied by flexure (0.5e: permanent defermationi.

600 but which n:s been specially prepar:d by va:uum Cr;dmg of the alloy Cr 179. Ni 77c is noH after o meitmp and has a ser. low c:rbon content. C = 0.002G me.tns of ter.ing..r.d th::t of in:onei 600 after o months.

(:cemer:ial:licy entam 10 t3 20 :mes as mu:h c:: bon).

I-ip. res ard 2 show tne micropaphic aspe:t of tne Th:s eura lew c;.r:cn t.'.iov ocha.es 3:mest the same as the cink:ng ict these tw o materiais. The crs:k:ng oc:urs commer:ial alloys. Also, tests.nade under dyn:mic condi.

tians (resistivity of the water maintamed const:ntly at 1 M

Tr.%tsd frem the I ren:h by R. D. M: Crit.'.t.

_G ';m O: 4 3 2.,

i.c '.10 " eratu'e 3 50 C l h2ve led to Vut h 11ner;:ve Atem!que. Centre d'E!uce. NicSce:.;;

Ihe 20: reLUI'0 U-

• t-T'*m p3ph5

'3 0I CrDide pre::=atien m = m.cr;;;! :nane'. (200, heren th: pain i e.rur.ay.m.hws. Fontenay-m hoses. F:2.e:.

1149

....W n

1 a==

. z.

v.!

g

.,>J.

N

., ;,}

%mlr g

h.

u,

.j j

8

.e q

~..,

7 v:..x\\s%.,b

. 3s3l, ;

g.h.

4

-. P,i(..

t irl:n u..

i f Cr 17%,Ni

.I FIGURE 4 Tra. sgranular cracking o aE'8 CI' (NaC1), at

• q,!

'/

10% steelin water containing 1 g.of testing (O2 <

./.

n six months d.

s.,

350 C after kg*8 ),

'N W"A.%

O M'TM';5W?M; WG. =M**%:

=.

'l

.2 i-y pQ d

..t~.'

i. t

~ ~.

_ j ',

i a.

'N

..a; 8

c

...+../

-A;-

?

v..- -,..,

?

N.

(

-s y,_,,,,.,_,

.L.:a...

g/, (oop o:

- 00g -

j:

'j' 4.

U

,s.

v.,

a..

.a :

a

'hi

"*i

. ~^

vu. 3...-16;.

.s.

ked after nine y;.

FIGURE 2 Alloy inconel 600 crac

't ular cracking of a Cr 17%,

months of testing in 350 C water.lloy are practically free

.. '.. FIGURE 5 - Intergran 77% alloy in water containing 1 g.rimental

~

boundaries of the extralow carbon asecond part of this article, the

(

after six months of testing expe discussed.(SCC) of high ef precipitate. In the d4).

same as those in Figures 3 an bfluence of heat treatments willbeOur research on stress corro (Fijure 5) in the 77%

ther papers.

nickelalloysis the subject of our o 600 (Cr 159. Ni 10% nickel alloy and intergranular Nickel alloy and in commercial evealed in the 15%

corrosien test Weter Containing ChlorideIt appeared useful to effect some stresserat 7SG). Transgranula: striations were r as Nacl]. Conse.

in deoxygensted water at high temy3)(chromium. nickel. iron) nickel alloy.The alloys with 25, containingwater at C1 additions {l g. 2'8 ntent varying from 10 not show any cracking.' Tests pe h t the nickelconte quently, a series of austenitic alloys *ith 17% chromium and a chloride high temperature.therefore,show t (0.5% permanent deforma-to 77% (Table 1) was tested. A the predominant factor in i these alloys. otality of our lloys with 10% and with 77%

the mode of stress corrosion under stress applied by flexure alloy 5 I

g twkel.The cacks are transgrenul.:r (Figures 3 and 4)in th austenitic ton). cracks appeared in the a in the interest 4

^ fes'ults points.out.

$2 - it:-

._g.g',

W.b (chromium. nickel-iron)'with in g

p{

(Ni 35 to 45%).

d Role of Various Parameter d

t.

with hich hi lloys ral The service conditions of a ter reactors i f,1 nickel content in pressurized wa well as that ut fi parameters. It is important to mined the to as

'?

p from the understandin2, the phenomen M

ueinp fi 25_.

N' s), heat treatment uur e played by the followig param wi:

'.h.

Cr 17%, Ni sariabic in the installat onular uns;tiza i

te:>

FICURE 3 Transgranutar cracking of a8 Cl* (Nacl) at kg ).

those involving intergranencoentered

'7 D' **l an water containing i g (. c350 C sher s*m months of t other rn::erials (often

?

pain size,and structure.

1g g"*uha *ttrapw!ated to 350 C.

1150

U Except as otherwise indicated. these studies have been performed at 350 C in water with a very 1,w exygen N'

"CO W content (Os < 3 pg kg<"a)) The autoclaves are made of and whose initial resistivity is greater than 1 Mfl cm.

50E IS/10 stainless steel.

g f

Relationship Between the Strest and r

the Time to Failure FIGURE 7 - Initial surface condition: longitu dinal This relationship has been studied on inconel X 750 f a specimen before test.

** 'o n which has the same basic composition as inconel 600, but

~~

with additforis'of elements for' structural hardening (Al,Ti, Sb). Cylindrical test specimens (e 2.2 to 4.0 mm) have been machined from a bar that the fabricator had heat

' ' ' ~ ~ ~

~ ~ ~ - -

treated in such a way to obtain a yield stress Ej,s,o c(3)

M,m

,p

= 80 kg mm-2.The composition of the alloy expressedin L.'r

~

b M

t percent is given in Table 2.

-%J-m Niemed Tasut z sc s.,-e = e o

e c,

em am s.

s p.

m w

FIGURE 8 - Specimen of inconel X 750 broken shu 2g o.o.

is.a ra.s o.ia nas omos u i.co tas on o = 1.2E.s o

~

02 Experimental Method. The stress is applied in tension attached at one end to the piston and at the other to a f

by means of the apparatus shown m Figure 6 and fixed point situated at the end of a thick perforated tube constructed entirely.of 18/10 stainless steel. This apparatus which leads to the bottom of the autoclave. By action of f

consisted principally of a calibrated piston.provided with a the saturated steam, the piston exerts a tensile force which cooled tonc jomt, and upon which the pressure from the is known by previous calibration. The diameter of the

?

saturated steam at the test temperature acts. An assembly exposed part of each of the test specimens is chosenin such f

of eitht specimens, fastened together with anchoring pieces a way that the test specirnen undergoes the desired uniaxial i

and electrically msulated by oxidized Ztrealoy 2 rings, is E

str a When a specimen fractures, a solitary finger of the

[

piston ::tivates a microswitch which cuts off the heat to u

I the fumace of the autoclave. The recording of the temperature curve allows the determination of the exact i

,s. -

time to failure of the specimen. After the autoclave is C"

opened, all of the samples are' examined by optical

]"A y

Ti microscopy. The cracked spe5imens, as well as the broken i -@ - - - @, 0 - pd. %-

II" ' H d Q ones.are withdrawn and repbced.

h., '7~

This method of tensile straining with constar:t load is rb severe. In effect, when a crack starts to form,,the uniaxial stress increases and this tends to acceler:te the cra: king.

..5.e e5 The surface preparation of the specimens involved a up i

I E

M 1 M finish machining (Figure 7) followed by ultrasoni:: leaning 5

i esd in a ternary mixture of acetone.al: chol-toluene. Diameters

- M

- {g '

'W of the. test specimens have been chosert n order to,obtain -

i

.m _

_.k Q -:G the foliowmg :rpplied stresses: 0.4,0.6;0.t,-1.0].2 Eo.a - -

a 1-a g1 350 C. (The prec:s:en of the diameter of the expesed part j b

]'

of the specimens invches an error of the calculated stress s

i h I less than or equal to 19.)

' I N Results. Frs:tures of the specimen (Figure S) result

?

4 h l from a ch:racteristi: intergranular crackinc (Figure 9). For 1: j each stress level, the result has been obtained from 10 to 20 test spei: mens and the results are expressed as the length of time ne:eswv to :=se rupture c: crs: king c: a gi'en

_l I

percen: ge uf the spe::r-ens (Table 3h FIGURE 6 - Autoclave with tensHe stressing appa.

We c'A ID25 d'2" 0 UNC f0f eMh $0Y 0

• ratus. Detail of specimen arrangement.

be.m; me :ppi: : s;ress and t being the leng h o i

necessan to crack 50~-of the s: e tmens (Ficure 10h The 1:me M :=;re in:re:ses sgndiesn b " hen the

re. ;eu s 'awer m fa:ter being much more : FO'I2GI Nhe resisuvity measured af ter operunt the astoclaves when the f0!sm' 4phedsl! M L hilheIU8e N W spe,:imerts have fractured was a:wn s on the order of 0.: M1m.

the sh.:;e ef the cune c =

(t) does tw in -

e*.ister.e cd a thres. q sts Ie.el beb M WM, O '11:e 's' note - This thenhand nomendture nd:.stes the

. eee:rse 0.M off set vt :J stress at the mJauted temperature.

weuu n:: e::ur te e.:n gn en.t.:cy.

I

~

{=.W.FNIMT.I.u,t)'.#-

@ttence cf Heat Tresement i

.:-- sp

--$h -

Nickel base, nickel.ch'romium.irnn a!!ovs shifer fro i

18/10 stainless steels by a smaller soluhihiy of

,,, ?.j, " *,

the austenitic matrix: thus. darbides are freipr:nt

,'7 i

f

~

- Q'T in industrist s!!uyp. It has been previomiy,it,,wn' tha

h,.

an inconel 600 type alloy, with a very low Earbon cunt 7,..s 7..'

' *l,-

(C = 0.002%), in pure water at 350 C shows a s Iy,;,:., p..

c 0

~~ c to stress cracking practically identical to that of commer

1. .i)'~7,

   '.C.,.

s'

~

Inconel 600 slloy in the quench annesled state. tilec J

,. ' ' -f '

-I a,,. 3 microscopic examinstions show intergranula precip

[*,,'s t G, J

in the commercist alloys, wheress the gram boundsrie

, ~. g. " 7 '. c. M 9 d,. :D the low carbon n!!oy are free of carbide precipitate

..J y :.

complement to this study,it appeared interesting to

~

r, <!

g O N.,.7 4 T*

examine the ocessional influence of certain heat treat, 7,..; ;. 4' p -?

I'[ "l,' s. Q U. W "5 O ! F /.., N P

ments, such as those ofsensitization.

Operating Conditions. The materists studied inciude

,. 9 l r p v -

'a.,.c,c..".

two industrial grades of inconel 600 and an slloy of the s

9* ;,, -r 1

• i

t. '

• • , e ;+'*

sp type Cr 17%, Ni 77% with a particularly low carbon yM i m ". ; c..+ '

..%u f' d$5l9 W'.15?lp,:...tg. ' 4. t

,,y.c,?, '1 content. The compositions, expressed as percent, of these different alloys are given in Table 4

. 6 W u.A.

l k

~

FIGURE 9 - Intergranular aspect of cracking in 7

inconel X 750 tensile stressed (a = 1.0 E 0.2 350 C) after 510 hours0.0059 days <br />0.142 hours <br />8.43254e-4 weeks <br />1.94055e-4 months <br /> in 350 C wat2r.

eass su ru sie s.o un um.

.u

,s.

su ui u.

==s, e. - nm one.. o en i.

o.i e.,

"- TABLEa s

a---'c " -

Test specimens (50 x 10 x 1.0 or IJ mm) were o

s:

descaled in a hydrofluoric-nitric acid mixture in a manner st to regularly ch..

"""~,"*."['""

minate about 10 gm of metal from each face.

-1

_m s

s ioos en m m m~

Jhis descaling is performed either after water quenchin

,, c before the sensitization treatment, when this is applied.:

u s o r so c so reo zio rio zoo no All of thg test specimens then undergo an activation 3

so n o.2:so c a

in dilute hydrochloric acid followed by a j

treatment use

.ie ano 22o

o os s onso e passivation treatment in nitric seid. A photomicrograph u

neo sio sio ano taken of each lot after descaling indicated the absence of om a ouso e so intergranular indentations on specimens so prepared.

aseo uno

.io o 4 t o 2 3So c

~

to The specimens are stressed in a horseshoe by cold

.no forming with the aid of a mandrel and a mold. The specimens t-then inserted in a stirrup and mounted on supports of the same grade of materist. These assemblies.

which are analogous to those in Figure 9 but without 3

g galvanic coupling are electrically insulated from the ii Du support assembly and from the autoclave by fritted slumina 6e Zircsloy for tests performed in lithium hy

. 7.,..r - -

r_

.p-'..

u i

j,,

The maximum stress of the external fiber at 20 C,-

evaluated by strength of material calculstions and by 2

{ ee micro-hardness measurements, is estimated at 180 15%

j E**

of the yield stress of the s!!oy before bending.

The starting values of the yield stress Eo.

~

for the M

various grades are given in Table 5.

t.

.t too TABLES ioco soooo I.)

oweet a.,

ewevu.e eu eessweatio, e..

..a 6

E.2 at 30 C in 0

kg rem <

A - Incones 600 FIGURE 10 - Relationship between the apph.d 40 t.ress and time until 50'3 of the specimens failed in a - inenei 600 water at 250 C. INote: X. axis = time,in hours, betore 24 fracture or cracking: Y exis = appEed stress).

c, gnoy 3 7p7 73 u

'. *, ]

k# Y * *o L ' E,#*$

U corresponds 13 sn industrial trestment cf incomplete soluhihty cf the carbides; (2) the quenched c;nditirn g.' j

• [I oj.

wineh is cbtained by a complete solubility cf carbides with

).p j.

.t\\p$g# I. /. -l. D j00

[

It

't.

the appr:priste..;at trestment, h:Iding ft:m ene'to tws f

hours at 1100 C followed by water quench; and (3) 4*

. 'q

[

4 ;:

r.

E l

sensitired condition characterized by precipitstion of car.

f, ** 4,,,

' 'l' bides principsily at gram boundaries after a treatment of -

W '*

tt,*,

f, f

4. s..

sy one hour at 700 C followed by quenching in heliur gas.

f',. *, g 9

)

For the specimens treated above. tensile tests and l '.

E electron microscope examinations were performed. Table 6

,4

.g 8

1* *

f..

• i

.r j

summarizes the characteristics of the studied alloys.

p

_}

1, e kn. - =,~ *- - =., er '.

i y

Results.-The proportiorr of-cracked specimens, as well

/

j as the elapsed time before cracking.are gathered in Table 7.

j mt.

,/,,.

5 p.

t

.n e

\\

t

._ ~..

[

4...

s c

o 8

FIGURE 11 - Alloy A (inconel 600) electron microscopic examinations. A1 = as received condi.

tion.

l

.~

u

\\

.;. ; q.. q W,.h.%'

..q 4

~

, W. 1 i....

-,~ 1,u.,..e* -

~'

~

?. :...

\\..

J.. N..

" ~ ~ ~

,,::.k.

~

~

~

~

~ -

• ~ -- ~

O

..;.'}.,

= =.

y q

l 6

- -- - 3'. s.

=

. ~.

5 m

~

D.

e

..ra

.M.

3

.:l:::::

5N i

The following points are concluded from these tests:

f (a) All of the alloys tested in the as-received state were susceptible to interpanular cracking. slthough the appear.

FIGURE 12 - Alloy A (inconel 600) electron

[

l ance and distribt tion of carbides were very different from microscopic examinations. A2 = Quenched in water after 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> treatment at 1100 C.

one s!!oy_tc r.s-ouenened _. anot.h.er.;. (b) the. sa.m.e. alloys tested in. the 2-r.

., - - = -

to in susceptiele..... terpanular. -,

c. :

- - = _ - - -

...- ; state siso--were-g.

3 i

crs: king. This treatment resulted in the complete solution ts'ted in the pain boundaries as is shown in Figure IS.The i

l of carbides and the absence of carbides in pain boundaries; susceptibi'uty of this slicy to stress corrosion is, therefore, f

I and (c) a _sensitizat_i_on_..t.r..e.at.me..n.t. f.ffe._:t.e._d from the ss.

~

~

practics!!y the same whatever its hest treatment.

d e

E received stste for. the two grades o inconel 6DO ritsrded e

stress cracking. In effect, under our operating conditions In//uence of Cous/ing with Other Metals

~

snd after 10,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of testing.no cracking was observed A study has been made on the influence of coupling at s!!in these specimens.

with mi!d steel. with stainless steel (Cr ISTNi 109/C <

a This behavioral difference is especially remarkable for 0.03 r). with pid and with p!stinum. on the stress specimen A (inconel 600). Crs:ks of samples m the corrosion of ineone! 600 alicys (psdes A and B) and a re:eived conftion were repeatedly observed after 1500 inconel X 750 whese :empos:t:en expressed in percent is i

hours of testing whereas in the sensiti:ed condition no

.even in T.ible 6. This alloy has a yield stress Eo.2 20 C =

Interpanular crs: king at s!! was observed.

84 kg mm~2 On tne other h.md. for s!!oy C: Cr l WNi 77'a. Wth a The speamens were tested in the s>. received condition e

i pe cularly low caroon content. (0.005 ). and wnh a (see tee 6> ::.nd dem!ed m a hydruf.uori nitric medium ur.i.tasuon treatment of 700 C. no carbides were prec:pi.

t th::kner rame.--2: 10 gm).

I153

~

l

.yy g.

o e

v ses %d' e

o

.~r P*.

.o y+-

p.

e g

.e.

./..

g Q*

.s ' -

R~.,/,.

~

s

. Y.

....k

~..

\\

-.- : ',. ' -~ ~ ~ ; _

.~

2.-

%.. - ~ ~

-y. %;p e......

.'. y -

u.d

/ g %

~

e

.k, s - ~, _ -

1.' q..

.,...[--

=-

, 4,,. '

/. '

6 e, -wd *. 4,.

e

.. ~

4

.. e W

....g 5 9

"':.. rv%

5H

~

..:. ~:.

1,'

.. ', j '.

p

- - ~ ~ ' '

"- ' M 4 -

FIGURE 13 - Alloy A Unconel 600) electron FIGURE 15 - Alloy B Unconel 600) electron microscopic examinations. A3 = Sensitized condition microscopic examinations. B2 = Quenched in water (one hnur at 700 C),

after 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> treatment at 1100 C.

3,,, y e. - - =w.

?.

, l.,,

, [.

-s

.4

'W T..~,-

.., ?

, h.y..

. ?.-.....

.,, s.,

..s..,

...,s.

c.,....

-r

} s ~~.

.h

.n.

.t a.

. ~..

s~

~

~

's

', ~ -. -

\\. _ _. 1.

j;'~

.s.

s.

e,.

-r

- y..:. -.- u

.s..

. p,.

-<.x*

t

.m

• ..Q

.' \\

\\

-r.

1 f. -....

y

.... w.

s~

a

. v,e, :. -

o,,

~ g} ~ s~:>.

y,

.m

-J^.

f.

9

,n.

r,

,r,.

7 5p 9s

/

o.g.

5p o

,1 t.

p

~.

r-

.C.

.._ a

.c_..

FIGURE *14 WAlloy B OnconeT 600) c fectron -

-FIGURE-"16 - Alloy B Unconel 600): electron -. --' = i e

microscopic examinations. B1 = as received condi.

mic oscopie examinations. B3 = Sensitized condition 4

l tion.

(one hour at 700 C).

i The couplings were made in the apparatus previously The results are summarized in Tables 9 and 10.

described, avoiding all crevice effects between the materials in water, the test performed with cold worked Inconel as illustrated in Figure 19. The stirrup and the holding 600 (Ej0[ = 40 kg.mm- ) indicates that coupling with screw are, moreover, made of inconel 600 in order to gold leads to the absence of crack.ing for the conditions and eliminate all parasitic effects.

for the time considered.

These tests were carried out in demineralized water.

Coupling of this alloy with stainless steel seems to h.ive whose initial resistivity was greater than 1 Macm. and in a slightly unfavorable intiuence, out this is not very clear solutions of lithium hydroxide whose pH was 10.5 a,nd under our conditions.

11.5. These various solutions were deoxygenated (0:.G 3 In li:hium hydreu.'e a: pH = 11.5. the etteet due to g.g. kg-' ).

coupiing does not seem to be detectable. Thi> medmm At each opening of the at.todaes for e.xaminmg :ne exercises a re:ardmpa: en on erae,.ing.

specimens. the resistisity of the water was on the order of,

s,_

After 12.000 houn of tesung in water.350 C, we note a 0.2 MO cm. The variation of pH in the hthium hydroxide '

'r ? ~' mtluence of coupling. grade 13 Ineonel 600 and solutions never went beyend 0.5 pHumts.

inconel X '750 with miid steel. The same conclusion.can"ot

c.s ' '. :.8.. -

a y.

u.

g s..T..*.,,.,,.

1

• w

. ',,.. s. :.

y.

.t E-J

3. '

.. ~

4,.

w.

3.y

. e.

.s r,,.

7 p'

e. : a

.. 3

~

• {

o.

1 tr

's

.-..- -.g

)

e6

}

p*'*

ps

'-~. ', l -:g -

?W;

- ~ t. -~.... e-

j. --

m&. :-

I D,.,~ 7. * %." s d'.,, -

' c, g

i 3*

l4 W

v

- ~.

• ~

n f=e C M.'.

• h.. '.'.%% ; ~ :~W {...,=

I g 1.

'.,s

~

t 9 '_

.ya l *.

y

.~

r.

I FIGURE 17 - Alloy C (Cr 17%, Ni 77%, C 0.002%)

A ciectron microscopic examinations. C2 = as received

~

f. h;*..

.. i.:.

. +. ':. '-""~ I condition.

- ~

-i._~

p;., c: -. -

e.

j

.f FIGURE 19 - Horseshoe apparatus. Sample of Inconel 600 (interior) coupled to gold (exterior)

~

• without crevice effect.

~

e

\\ s'I

,ms,

m.e te..mee

.us i-v~

son an.

en an.

.n.

U

.n

.n i

5p o

TABLE 10 (incoael 600 Corresoones to Alsev B m Tetne 14)

.V:-.:,5*.^.'.~..

-a teven.w of Sam,ones pr.cked After 12.000 Hoses

'"*"""*d**'"*'

FIGURE 18 - Alloy C (Cr 17%, Ni 77%, C 0.002%)

m. crc===,vl i

. r.

electron microscopic examinations. C3 = Sens.t.iized i.

Yv erw l..oM st pH - 10.5 8

cond tion (one hour at 700 C).

...P.*..

trconel 600..

019 0/9 j,q

-.c-TABl.E 8 -

• i conet 'x 750 0.s '

O.9 j

n (Compostiors: E xpreued in Perce.,tl inconu 600 0/9 0/9

• ** ' #d C

Cr Ni Mn S

F.

Al Ti inconel X 750 0/9 O/9 C.05 14.7 70.9 0.10 0.C5 6.20 0.66 1.96 incoes 600 0/9 0/9 Cowpled to platinur9 tecocei X 750 0/9 C/9 he made from In:onel 600 coupled with 1S/10 stain! css inco e 6oo 1"O 0 19 casonec to 18:10 3*..)

sta.nkeu stee:

incone X 750 O r9 O!9 l'!:vence of Grain Size i-u- ' 6m

'"3 /

"O Some tests were perfor--.ed en In:onel 600 specimens

' ' ' ' ' ' ' ' ^*

h a rei tisely large erain size (between 200 and 300 pm).

T:.re specimens were desc.: led in the hyd:cQuori: ni :::

..ee..

x 750 cr 0 ces

d medium (thickness :emosed: 10 gm).

I155

. m,...g s.

f

},....

M l

e,

\\.

.<\\ W

^

c.

• 6 1,

p N

.S

. (

i

.t

.=..#.....

3 L

[te

• N.

'\\

r

.,. ; M

\\[ '

g Q

\\

['.@* y

, s, k

l.

o e

y c

,.r

.s a

b 3r,.

Er

<>.C3 h

yp,

4 s b.?.D,50 p,

.A j

'd *f*4 0 f.,

• FIGURE 20 - Intergranular cracks (paths AB and

'f CD) obtained in inconel 600 with very large grains.

'.'. t

• p

,~, f j,'

AB polish with diamond paste; micrographic attack 1 3 v

(aqua regia and glycerin); CD polish with diamond

)

?','-,.j_ J Q. {.,

I parte.

t FIGURE 22 - Tensile specimen (a = 2/3 Eo.2 300 i

B".

8.a =- Gypi_C.riece+S. WN

~

C) after 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> in 350 C deoxygenated water.

intergranular rtature of the crack.

\\

\\

(

i 1

l MarA.:: vypp,

, w:. --

j l,

NF1 M

• k..,,..

. ~. -

f':.,~.1' .-... % 4 ; M., s. -g

s.._

4.Ty q .o r s '. 7,.'.. -. = a.<.

• e V

m .A - ~ ~ ~ 7 A./ .b, ~. m..- i I .e3 y. p_, . %.f. h 4 ~ 4;;;"f,. c{g.,., e. Q... M... \\*., A-c h:.,'f =8"

s..

l ....2 .it e

25p, g:-

.j j- ' -..r n..,._.~ ... n.x.g 3 ',,- - + Q 'W) l N ~.%.. - N. J -.7* -N ~ s g M 4 f"3 FIGURE 24 - Intergranular cracking of a bend .' r

g. ; y#

1 specimen (Eo.a 300 C = 68 kg mm-2) after 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of testingin 300 C deoxyynated water. - D., _.W h * */. s.} $ $,.;**. - km. m. j,' $,5- .. h.h.,. 4 { [4 The following resulted: (a) Tensile specimens stressed y .f. Mf; j,. *, ~~ b,.. p *y f ; q r

• - F Ni i

k. .' N s~aak '25 '. H= sin;,4 to 2/3,3/4, and 1 Eo.2'300 C, with or without notches, k were all broken by.an intergrammlar process after 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of testing at 300 C for thealloy heat treated to the [ strength of 86 kg mm'2 (Figsre 22). Specimens with lower mechanicai properties (681 mm-2) did not crack FIGURE 25 - Intergranular aspect of cracking 3 after 6,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of testing;(b) Bend specimens (0.5% cold (inconel 600 type alloy). permanent deformation) underwent intergranular cracking after 2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> at 300 and 350C,whether the metal was heat treated to 86 or 68 kg - mm"). However, this Fe #< ~7'"%TM ~ cracking was clearly more severe for the alloy with higher P 7,.-.~., j. ^2 t s. [ mechanical properties (Figures 23 and 24); and (c) Some g; "_./ g bg g/T.[-j,J%,$.4 NN 7-M bend specimens, made from sheet material which was . '. /C i quenched after solution trestment (yield stress.35 kg,. W TT' A E: ^4 k S mm-2), did not show any cracking. These tesu went I - S.3 % ' beyond 8.000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> at 350 C. Y.K 7%q.i j'34 A ' g '~' 9 'C. ">"]; 3.E p.,) These results confirm that inconel X 750, in the ~, '. hardened state, has a susceptibsty to interganular stress C. cracking much more severe than the homogeneous Inconel s../ (,. Nf.% M3 600 alloy. Furthermore, the role of the structure factor is g$;- p"f(t 'r t g.% 'i noted since the susceptibility is peatly lowered when the I intermetallic precipitates are decreased in number and the '/[..-'l - p./ %4 $f,.[,. a resulting mechanical properties decreased. In the extreme s j case, Inconel X 750, in the quench after solution annealing '[. j%;,i s a.y@/d. y(.'E, 4 .;'.,.p S condition, seems to behave sirrularly to inconel 600. g.f.

1. ~ f.4 @

ex 3 y Observations ort the Cracking Process- "A .J"..,' .... "M Role of Sulfur.

u. t;%g

_ 3 :- '._ g...,

~--.

. l'..,

S canning electron microscopi examination and 50 p' 9k I,$ analysis of the emitted X. rays bear on the interpanular cracking process for the alloys studied. -(' t,g ,tf The samples examined were cracked under stress at 350 C in demineralized water (O < 3 ug. kg-8 ). Inconel 600 f 2 in sheet form was bent (0.5% cold permanent deformation). Cracks were produced between six and nine months of FIGURE 26 - Transition between intergranular t testmc. Inconel X 750 in bar form was tensile tested (0.6 E cracking and brutal ductile transgranular fracture. (inconel 600 type alloy). 0.2 350 C). Fracture occurred after 800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> of testing. The followmg points are made from the test: (a) Sb:rofractography confirms the micros:opic observation th:t the cracking is intergrant.lar in nature (Figure 25 L This presence cf numerous crystalline precipitates at the pain crsing is then transformed into an aspect of brutal surfa:e is noted. These precipitates :re dispersed or in fr::ture of a du: tile t.ansgranulst type (Figure 26h (b) m agpeptes in platelet or rod-lAe form (Figures 7 and 25); the propaption zone of the interpanular cra:k. the (c) tnese precipitates have a tendency to be more abundant b 1157 ' b: "s . 't-M

• • • F.c'~e. A -T

n.~- ~ N'm =- V n' =* "m"e : ':."v- - :-7. c,c m u./iy.g -K. .M,. i M 4.,. '.% p:a ny.:

3....- - O.,..n;

.t.. M..~.:y mn T.W,i\\

.v$..,.g .,..,4v; 7.n.. k. W.... .. g wwwp-

g. e n d^l

.n n. E u.1- :;..&.: ...1 w ~ ~- - n -. = - ~., b* I.'.:i*%.# /..;? ** .w{.} I .\\.\\.\\ [ \\\\ I.Il\\ .:e ., a.a,..... u .a e .w - Sa=== 8 *

• c': 8-q

.m. ? >.s., ya. e W.= ~ - m., .-w.-- .~ s Q ,.s N

• A ?.

'.w s s .,, A,'*p' 7 - r. 7,. [hN gr s p-. G* %7-FIGURE 29 - X. ray emission spectrographs. Precipi. \\ '. ','.? e *

• i.*

tates: a = aluminum; b = sulfur; c = titanium; d = W.)' . f.>s,f. %, ".;; m. n. -[). chromium;e = iron; f = nickel. g;, ~~- 5. ". a y I

v. s

..~.*?. precipitates reveal that they are very rich in sulfur, j,.' ) ,d. :- 7 ? } f,Y).. J k;.

(

frequently in nickel (Figure 29), and that they can also Y I..'h 7 j i $ ' }9 " d,,41% -[q electronic image, confirms this point very weil(Figure 30). l d' \\. contain some iron. The X.rzy image, compared to the p ' W-Jm,..kl. . q f ' According to our observations, it seems possible that "N i i.. J. p. a. - 4

k. g X.*

L M;

• Intergranular cracking of the alloys rich in nickel, such as Inconel 600 or inconel X 750, is reisted to the presence of l

sulfur containing compounds in the metal.We can make the i FIGURE 27 - Precipitatn st grain surfaces on flanks comparison with the properties of nickel, even high purity of the crack (inconel X 750). nickel, that is embrittled at grain boundaries by segregation -t-- of manganese and nickel sulfides, this occurring for a sulfur f~3f content as low as 0.0009%. a in the alloys containing 75 to -f % 'J =. '1G*j ... ~ t.M;N [i F..Q - e g 77% nickel such a segregation is thought to occut. These fQ?- compounds, which are probably unstable in water at 350 C, { 4 _ lead to the formation of a strongly sulfurous medium in \\ 1 g gMg 'r J.y;g, y g' g u the small metal volume at the bottom of the crack.This i I ^-3 4' region would then be favorable to a rapid point by point

• t

f. p g.i g~' p:.

g .r dissolution of the nickel rich alloy. Precipitates found on i ,.. /. the flanks of the crack would be products of this reaction. ( %s p4 g@. - N d 7~,h W) ' 5. yf.,;.7 ".. phenomenon is rather specific to alloys with a high nicke! 'd6"~ s This mechanism would explain th?t the observed 2.:S 3rf. N. (./ b

• '4 content; therefcre, if the concentration of this element was

-4 ' M j. lowered, the process would not occur. w , - Jt Funhermore, since the nature of the sulfur compaunds f, h [ W

g. p

,%j and their distribution in the alloys are not controlled, great I ,l; f[,,% ".N ' 9 ] fabrication techniques. This would explain the apparent / differences should be produced by different melting and / T .j ',, k ^ ?O. N ',g k ~ divergencies observed between different batches with the / 'G.. same nommal composition. / =- - ' hri sbns 1 SYS i-q'% i L-

• .!ae,5p

h. v f 'i N

• t 3

.,Y N Different service conditions for " nickel. chromium-Q* 4-i- ?? < c, qw iron" austenitic alloys with high nickel content, such as i M s 33 Inconel o00 and 'X 750 type alloys, exert an important p l 'W bP~Ay% l F E influence on the susceptibility to intergranular fracture of these materials in water at 350 C. The following points are made: P FIGURE 28 - Precipitates at grain surfaces on flanks

1. The time to failure of Inconel X 750 increases cf the crack (inconel X 750).

sharply when the stress decreases. However, it does not ~ appear from our tests that there is a threshold stress below which the phenomenon is not produced. Cracking has been a in the zones near the lip of the crack.They become rare in observed for a value as low as 0.4 Eo a 350 C. i E l the neighborhood of the propaganon zone and are non.

2. Certain heat treatments can strongly influence the existent m the rne of brutal fracture. They are not behavior ef incunel 600. We have sho n that a sensituation observed except m a few rare c:aes on the external surfaces at 700 C, although producing an intergranular precipitation of the samples; and (d) analys:s by emitted X. rays :f the of carbide, notably slows down the era.: king process.

1158 ,..-,,u* 4 ,g - - - -1, water at 350 C. hnWever, the appearance of some intra. ~ 4C & g "-T.- ;*

• b-granular cracks was noted on 'certain large grains.

f >[c .[-

5. The influence of the structure 'has been shown

[,., I * [- h,"*%,f.-

• T, '

alloy inconel X 750. The susceptibility to stress ,4 on ,Q. ,.\\\\ e y. 5 corrosion decreases prestly if the intermetalhc precipitates p \\ '. .,*. Q become less numerous and the resulting mechanical i' ( 3[

• properties decrease.

/, F.

6. A mechanism is proposed and related to the

, 't .'.E presence of sulfur containing cormoundsin the metal.This f'. CC C YNI C ;.,.Q.':'[2 can explain certain of the observed phenomena. .c y. 4, ' -.,e., h - h - -.i.i.-- Thus, the compiexity of,. industrial installstions"in.M..;_. jq ., ~~"j evitably leads to the simultaneous intervent,on of numerous i .T parameters whose interactions can be contradictory. Conse. gl*. ;,. d, y.3 s. j[ quently, the real service behavior of Inconel 600 and X 750 g,p/ s '. ~.. .A - k. - type alloy will be apparently quite variable;it is, therefore, .d'. - 4 7,'..'..d.,.l wise to adopt the greatest prudence in their application. -G--- q O E. F i. ja.C.'.,p._SM.m / v. ~ E# Acknowledgments 5.# r . %.)$ E - - , Es i .. &... (z.hrE t' '$b." W.. ' D ' for the scanning electron microscopic examinations. M We would like to thank Madame Meny and Mr.Olivier .N ~~ ~ y,4 c u a29: / --x. 'pt7.v r-s.:;~p w r: @ c w References ~" - ...;. Sl q:-f.:. Sw.- W V y-; = c c.,'.J.f.*p.rc fdc.3 i,- A -;.it. c M

1. H. Conou, L Gran. Y. Le Galt, and. S. Vettier. Conosion s,ous

s'f-

./. Q.;.

.. 'ri.' ,' N :-.%. f,;$M --3 gg; e.-U.d contrainte de l'inconel dans 1*cau a haute tempenture. 3eme se. -n , i-*.*. ;.' 54 '* WUD"".W %g..g J Colloque de metallurgie surla conosion,Saclay. North Houand y'..s_' E {'.2 "*

• M Y~ [Y, '. [ M,,-. 8 ' 7.{

4 Publishing Co Amsterdam,p. 161 169 0 959). .'..%, 7.3 R .. M.., ...v.. o.-r. 3.: '. -dG.T.'..'3

2. H. Coriou, L Gnaa. M. Pelras, and S. Vettier. Fissurat. ion sous contrainte en milieu chlorure et dans l' eau pure a haute

r,.f,

• I*f....'.?

. 7.2.:. c. " M M temperature d'auisses inoxydables au nicket Communication -c.3, 4 ^. c -' "'W[.[I %'-bT,,5,W,-Mh pre'sentee su Colloque de la Socie'te Europe *enne d'Energie i' .._ jQ.] 1p@y. M -:f.>.i_^.','.r. M S N. Atomique, $t udsvick. May 22-23,(1962). [ ~.. ~. of %* *'g

3. H. Conou, L Gnu, C. Mahieu, and M. Peltas. Sensitivity to stress corrosion and intergranutar attack of high nickel ty.pgr

. #.. _.,, w.' 2. -. )4 f, ....J, austenitic alloys. Conosion. Vol 22, p. 280 290 (1966).

r..

v- .d

4. H. R. Copson and S. W. Dean. Effect of contaminant on g

.~s 4-7!.g 6 ..~ W 4 resistant to stress corrosion enckmg of Ni-Cr Alloy 600 in M ' - f.VF# ~ '.I pressunted water. Corrosion, Vol 21, p.1-8 0966). 5 ( j' ~ V-

5. G. G. Foster and J. W. Taylor. Stress ass sted conosion of r-j inconel 600 heat exchanger tubing in high tempeature water.

s (, g.'- 9 Institution of Civil Engmees. Confeence " Effects of environ-

• ~~

s .q ment on matensis propeties in nuclear systems", London, July

• .,.} : (.,.g&.

.a 1 2,1971. .- j. ~ /., Ty~ ~ c.,.

6. R. M. Rentier and 1. H. Wetmsky. Effect of HNDa IIF pinhng L. ~, 9..

",I ~ ==><">c"^'' *. =W A PD.T M . Di t : : - :.r _. :..< -. my gp 944 (1970) October.

7. H. Conou, L Cull. P. Olmer. and H. Wil:emoz. Influence of

~ carbon and ni:kel content on stress corrosion cracking of sustenaue stamiess anoys in pu e_or chlorinaiahter as 35(Lf' .. i f *-. - ~ FIGURE 30w_ Electronic imagesiabove) andW rays Pw s of-CW-em Fundamenta Aspe:ts of Stress "" (below) from the same zone of the crack, showing the Cc: osion Crack.;. Coiu.bs.1967. Ohio St:te Univesity, association of sulfur with the precipitates (inconel X M CE 0969L 750). S. H. Coriou and L Grau. Stress conodon crackm; of high nickel austenitu alicys. Nato Conferert:e on the theory of stress

3. The important role played by certsin galvanic cortas on cra& ; m allo > s. Labon. Nuo. bruneis 0 971).

effects have likewise been shown. Contact with a noble

9. G. Bonde'. H. Convu. L Grail, and R. Whut. Inter; anular 5"

• 5' ' " * #2 D # I "'* "'I X * '" * * "* *d * ""

metal. such as Fold, exerts a protective eficett contact with n 3W C. b ACL An-.M W un;:. Chw.nm TIM 1) Mar:h. c:! ben steel leads to a strone accelerstion of the erscking

10. u. Hubner, b..;hamon. and M. Pourb.m. Studies cf the process. on the centrary.18/10 stainless steel may have a 3,.g.n.y g,.

.,.y. g,,u.,, _..g n,..g ; o r 3.;,. e nia: slightly unfavorable influence. However, it is recalled that i,.c. 9 gig.a,.,, j.,...m. un g 3m. c p,,y, q:3, the inCuence of these various couplings has been deter-n nedc.ig,i 4 e ~. a g ue u;;. s p ermp.sweeen u s 2), mme/ in the absence of crevice effects. These effects can li. H cenou.e 1. cra %eme, p,.,w, rar o anose. was perturb the cracking phenomenon.oecasions!h acceler: ting a trai.te J.- .mes.:uuenm e d.n I s equits t 3:, d ea. pour.. ;r.L t.e evnerve. Ce'ee.ee pr:s:.'ee :c 1159 l -w.#-- " h AT J ,of hish purity nicket.Trans. ASM, vol. 53, p. 349 (t961). Our comments will incMe a very brief review cf cur test results en inconel 600 and then we wish to rsisc a questi:n en the SCC behavior of lacunel 600. DISCUSSIONS In our laboratories, investigations are in progress to determine the long. term' SCC chsrscteristics ofIncunct 600 .!. H. Westbrook, General Electric Corp.: 'At the Montreal grain boundary meeting next in the boiling water reactor environment. For purposes of m: nth,0) Dr. Floreen and I will report some results on this review, only the long term test dsts will be presented. } highly pure Ni-S binary alloys which I believe are very complementary to and confirmatory of the very interesting 3,,,,,,,,,,,,c y ,,,,,n,,,,,, studies you have just described to us. Our allqs ranged t e usi..e sso s v s. g s from about 20 ppm S to tess than 1 ppm.S(!)and we were w r:onitoring the grain boundary interaction with S by the rsicrohardness technique we have previously reported (Acta ".,*~~.".C'~' EE Cf" ,,',",'o,,

• s a-- o '

. Met., Vol.17, p. I175 (1969)). Quenching from 900 C

~~ g' ' --"C" gg[l sh

ws no grain boundary hardening for all compositions; C Z ',*,",",",, ""'" '**. R% %',

sliw cooling from that temperature shows an amount of ' ~ ~ - - - * ~ ~ ~ ruw.n hardening decreasing with decreasing S but still sensible at 2 <1 ppm S. Reheating, after quenching, to modest tempern m,,,,,,,,,,,,,,,,,,,,,,,,- tures (100 to 700 C) brings all alloys to a steady state grain boundary hardness whose value is a* function of sulfur in the test program, a uniaxial tensile specimen of contint.The kinetics of this pain boundary hardening are Incenel 600 failed by intergranular stress corrosion in 550 such that it is impossible to maintain a soft grain boundary F water (0.2 ppm Oe,0.5 ppm C1 ). his specimen was at room temperature for more than a few minutes following tested at 125% of the 550 F yield strength, he specimen a 900 C quench. Derefore to examine the possible effects was of a cresice configuration, Le.. a foil band of Inconel d sulfur-grain boundary interaction on a bulk property,it 600 was wrapped around the gage length and the failure is necessary to make measuremenu at sub. normal tempera. occurred after 6633 hours0.0768 days <br />1.843 hours <br />0.011 weeks <br />0.00252 months <br /> in the crevice region. Duplicate tures. Accordinpy, tensile specimens were tested at liquid companion specimens have not failed after 11,477 hours0.00552 days <br />0.133 hours <br />7.886905e-4 weeks <br />1.814985e-4 months <br /> of N 1:mperature for two conditions:(1) slow cooled from testing. Other creviced specim' ens in triplicate have not' 2 900 C, and (2) quenchM from 900 C to ice water and failed after 11,477 hours0.00552 days <br />0.133 hours <br />7.886905e-4 weeks <br />1.814985e-4 months <br /> of exposure at stress levels of 125, immediately to liquid Nr. All alloys for condition (2) 150, and 200% of the 550 F yield strength in simuisted showed 80-90% RA and predominantly transgranular frac. BWR water (0.2 ppm Oe).These tests ne continuing. tute. All alloys for condition (1) showed much reduced RA Rese test data form the basis for our question on th.e figans in the range 3010% (the more so the greater the S ' SCC behavior of Inconel 600 which is related to the effect content), and with accompanying hieresse in the propor. of temperature on the SCC of Inconel 600. M. Grall tion of IG failure. Although these experiments are purely presented test results on specimens exposed at 300 C(572 mechanical and not electrochemical, they do show quite F) and 350 C (662 F) while our tests were performed at directly the powe:fel role of even very tiny amounts of S 258 C (550 F). We would like to ask Mr. Gran to comment and its interaction with the grain boundary. Whether the on the possible existence of a temperature threshold below latter phenomenon is properly to be regarded as equilib. which SCC will not occur? rium sepegation, vacancy promoted nonequilibrium segre-gation, or conventional precipitation is yet to be deter. Authors' Reply: l mined. Perhaps each plays a role in its proper concentration As a matter of fact, we never performed experiments on Inconel 600 at temperatures below 300 C; most of our-range. work was performed at 350 C. Taking into account the gener:! scatter observed, the Authors' Reply: incubation time, for example,we do not consider that there nese results are very interesting. Thank you for reporting them. They show that sulfur undoubtedly plays is a significant difference between thr. results.obtained at. en important iole in'the interpamilar pWesses ih nickel these tivo temperatures (300 and 350 C)in high n:sistivity, i and presumably in high nickel alloys. deoxygenated water I For lower temperatures,and in different environments, tne possibihty exists for a lower suscep'ibihty to cracking. t U)&w published, Canadian Met Quarterly Jan/ Mar (1974). but we have no dsts to support this. l l I160 ,