2/27/84Joint -

s

~ ~ ' ~

d"4TEC C0;iliESPOllDMCEUNITED STATES OF AMERICA gg-

NUCLEAR REGULATORY COMMISSION U EO-

'gg 0828BEFORE THE ATOMIC SAFETY AND LICENSING BOARD

%:47In the Macter of ) l' ( ;:- .

-y . . . . . ~ ~ . , ,

bi,k/h" '' .METROPOLITAN EDISON COMPANY, ET AL. ) Docket 50-289) (Steam Generator Tube Repairs)

(Three Mile Island Nuclear )Generating Station, Unit 1) )

.

.

JOINT INTERVENORS RESPONSE TO LICENSEE'S SECOND SET OF INTERROGATORIES

Responses are here provided to Licensee interrogatories using Licensee's

letter, number designations as noted in "II Interrogatories".

A. General Interrogatories

II - 1 Norman O. Aamodt prepared all interrogatory answers.-

II - 2a - No proposed witnesses are named.

B. Interrogatories on Contention 1(2)

II - 1(2) - 1(a) -It might have been a_ cause.

(b) It may pose a significant threat of future IGSCC.-

See " Observations On The Cracking Process - Role of ,2(a) -

'

..

Sulfur", Pg. 1157, 8 of " Historical Review Of The

. Principle Research Concerning The Phenomena of

Cracking of Nickel Base Austentitic Alloys" (hereafter

referred to as "The Paper" (attached).

(b) - See subsequent answers.

3 - See answer to 11-1(2) - 2(a).

4 - I do not know.

5 - I do not know.

6 - NA

PDR ADOCK9402290000 840227+

05000289'OPDR

_ . - - - . _.. -- _ . . . - _ _ . -

..

..

paga 2

7 Hot water, some oxygep, some tensile stress and time.-

In essence, the IGSCC is " incubating" with time being

the key variable. With high nickel content, some

moderate level of carbon and even trace amounts of

sulfur, sensitized Inconel 600 will crack in'an

aqueous environment which is not free of oxygen.

8 The Paper.-

All operating conditions.9 -

The Fcper; see answer to II-1(2)2(a).10 -

11 - Scme as 10.

Rate of IGSCC initiation, or time to generation of12 -

cracks, can be expected to shorten with increased

nickel or sulfur content, increased oxygen or chlorine

level, increased water temperature and increased stress

level.

13-(a) See answer to 12.

(b) I do not know outer bounds.. -

'14 .See The Paper.-

I do not know, other than those that cause increased15 -

oxygen levels.

16 NA-

17 - High nickel and carbon content.

See The Paper.18 -

I do not know; " coupling" effects described in The Paper19 -

may provide clues.

20 NA-

f

21 The Paper. It is short and topically developed as-

discussed above.

- -_ _ _

. _. _ .

.

. ..

paga 3

.

22 I do not know.-

23 . NA

24 Yes-

.

25 - oNote (2) of The Paper.

oNote (5) of The Paper. Note absence of contaminants

in aqueous environment.

oNote (6) of The Paper..

oNotes (P), (9), (10) of The Paper,

oNote (11) of The Paper..

-

26 I do not know.-

27 NA-

I do not know.28 -

NA29 -

.

See above answers.30 -

31 - I do not know yet.

I do not know yet.32 -

I do not know yet.33 -

.

'C. Interrogatories on Contention 1(3)

I allege that islands of IGA may be precursors of IGSCC,11-1(3)-1 -

that all that is needed for IGSCC to develop may be

a additional time for " incubation" to be complete.

-2 - See Note (1) (Fg.1149) of The Paper.

As noted by Third Party Review, IGSCC was frequently observed-

in areas of concentration of IGA islands.

Threfore: Role as precursor is reasonably ' deduced.-

t/

*,

4

4

-

.

. -

Fags 4

3 - Yes

4 'See answers to B.-

_

5'

Yes-

o Additional exposure to oxygen, chlorides, lead, etc.6 -

might shorten "inclubation" period..

o I do not know which elements or compounds could serve as,

synergists, nor their concentrations (though trace amounts

would probably suffice for synergistic effects to occur.)

o Fotential corrodents are described in Third Party Review of7 -

The Paper,

o Synergists - Personal experience with anti-oxidant systems.

See 7.8 -

I do not know yet.9 -

I do not know yet.10 -

I do not know yet.11 -

I D. Interrogatories on Contention 1(5)

Low valence carbonions which could mimic activity of sulfuiII 1(5)-1 -, .

(.

in sulfide forms.

!

2 Chemical similarities of carbon and sulfur.-

| 3 o Valence lower than 4.-

o " Carbonaceous" is almost meaningless apart from the fact

that carbon is present in some undefined form (s).

- 4 - Yes, possibly.

I do not know and, unfortunately, GFUN does not, nor is it5 -

evident than any one else does.

6 NA-

-e,

'.

. .

Pcge 5s

7 Same as 5.--

8 NA-

9-a- I do not know,

b- I do not know.

c- Mechanism probably would be similar to that with sulfur.

I do not know what synergists might be present.

10 NA-

11 Any and all that might occur in the system. Note: A-

" synergist" is not a synergist if it does not produce a

. synergistic effect.

12-a- I do not know, but GPUN should.

b- I do not know, but GPUN should.

c- I do not know, but GPUN should.

13 GPUN should know whether or not synergistic effects are likely-

to occur (or have occurred) if GFUN is to develop a suitable

confidence level with regard to any prediction of anticipated

IGSCC initiation.

14, 15, 16 - No questions. .

17 PhD., Chemistry, many years on Staff of Bell Telephone-

- Laboratories, inventor of various chemical systems dependent

ou synergistic effects, widely published. I do r.ot have his

resume.

See 17. This work supports Contention 1(5) ia that the18 -

operable element of expertise is knowledge of synergism, per

*per se.

19 I do not know.-

20 NA-

_ - . _ . - - - . . _ - - _ _ __ _ __.

- -- - .

.. .

Page 6

21 - If we should use Dr. Hansen as a witness or source of help,'

I will provide this information imediately. I do not have

access to this information at this time..

22 1 do not know yet.-

I do not know yet.23 -

24 I do,not know yet.-

,f

./ s

A $Ft44$u (/ /I,41/W Wj

Norman O. Aamodt for Joint Intervenors

February 27, 1984

.

b, .

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a- - . - . - - - - - , - - - - , - . . ~ - . . . , . - - . . - , , - , - - - - - . . - . _ . - - _ _ - -

y_-- m - ~ - er , -

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l 4../. M <.:-d,M U 'O M=g/* ,. .

MJJ cwa C- A.- <.s .M:-, MWE % y' '

HISTORICAL REVIEW OF THE PRINCIPAL RESEARCH sr J ~.,a~:-'

CONCERNING THE PHENOMENA OF CRACKING OFUNICKEL BASE AUSTENITIC ALLOYS )

J. Blanchet, H. Coriou, L. Grall,C.*Mahieu, C. Otter, and G. Turluer' - - ~

- - --- - '~ *-

.

In a number of studies,'-3 we have shown that austenitic w w c_.p % M4W M M.-Me.mP F N,-Q/

-

"Lalloys (nickel-chromium-iron) with high nickel contents (Ni-

. 1.= 77%), such as inconel 600, are susceptible to the | 4~

,

phenomena of stress corrosion. The cracking is essentially [ Q --

.i

int:rgranular and appears in deraineralized water, at 300 g} ,

.:.

'' T* -T - -and 350 C,in the absence of oxygen, chlorides, and tracescf certain harmful impurities (lead),' and at the bottom of '

.

recess zones. It is sienificant that the period ofincubation @ p Q-~

u-

'(.G.

preceeding the apoearance of cracks is long (on the order of1 2

.

-several months under our expenmental conditions). Inconel ' ,.

600 type alloys are often recomraended for the construc- /' *i.

~-

tion of various reactor components that undergo stress: steam _ ,

'

- -

generators and internal structures of high-pressure water g-. , ,'

reactors. We will review some previous results in the first - I .;1~part of the paper. .

.,

.- f .: ,

4 Tests in Water at 350 C p., j ;, . 4'

v .; -

4',

.,,'--n -iThe nominal compositions of the alloys are as follows:

(1) Cr 17%, Ni 10%, (2) Cr 17%, Ni 35%, (3) Cr 17%, Ni ;45%, (4) Cr 17%, Ni 77%, (5) Cr 20%, Ni 45%, Mn 5%, and ...k.5

,

(6)lacone1600. Q \ f gE-

~

; ;i -

We have performed experiments with I mm sheet ai' -

specimens in the quench annealed condition. The exact / . ..

compositions of these alloys are given in Table 1. t -

. i.J.- Y - Nj

, _

Ti ,,,,,.,,. FIGURE 1 - Alloy Cr 17%, Ni 77% cracked after she.,

,,

months of testing in 350 C water.~

.

* ae . e o em m n sa, s p.

ine o o ois su ina ~s os o oie -almost always interganularly wish, however, a few rarewn oors 37,3 - su os o.s emo a-

e.- EM .% unsgrapular paths.for.the alloy.Cr.17ANi.71A'Ike other.I. . - . U . E. Ei. In$ . .I$ . 1. ~,r t

f^-'' " " g 1;2 '*f aj -{-f J."' C ' alloy types: Cr 17%. Ni 10%; Cr 17%, Ni 35%, Cr 17%' Ni '--,

45%; and Cr 20%, Ni 45%, Mn 5% do not show any.

{cracking whatsoever after 10 months of testing. Other

sPure Water resesrchers ,s have tho eroduced stress crackingin inconel-

These alloys have been tested under the three following 600in pure water at hich te neerstures._,

conditions: (1) medium: demineralized and deotygenated it is noted that cracking as shown in ?igure 1 occursin'

i water (0, < 3 pg kg-');(2) temperature: 350 C,and (3) an alloy whose composition is similar to that of inconel'

stress applied by fiexure (0.5% permanent deformation). 600 but which has been specially prepared by vacuum

i Cracking of the alloy Cr 17%, Ni 77% is noted after 6 melting and has a very low caebon content, C = 0.002%i months of testine. and that of inconel 600 after 9 months. (commercial alloys contain 10 to 20 times as much carbon).

{hgures 1 and 2 show the micrographic aspect of the This extra low carbon alloy behaves almost the same as thecracking for these two materials. The cracking occurs commercial alloys. Also, tests made under dynamic condi.

,

i - tions (resistivity of the water maintained constantly at 1 M'

Nranslated fro-n the French by R. D. McCright, f!/cm, Os < 3 pg . kg-8, temperature 350 C) have led to

( 'Commhs.irbt a l'Energie Atomique. Centre d' Etudes Niciesires de the same results.' Electron micrographs reveal carbide*

l'ontenay sus Roses. Fontenay-aux Roses, France. precipitation in commercial Inconel 600, wherer.s the grain'

P

3 1149

.-

'# a

. . , .- % !.* .

D ., my )m,,/ -;a*

, ,.

W .! ,., . , 1 -' *

,/.

o_

'''

i*- , , ; '

- .- .* .

1 s ...>w.m-

N.:,.?, ,, i,. . * ' ' '

i -.. V '$. . ..

, 2,5,,v, ,- .-

''

3._. m. , .*. *

M : d. ~J,._./ .

-t " .

.. _-: -. .'

m.t , Cr 17%, Niy

~ f * h.f FIGURE 4 Transgranular-cracking of au": w .y. % -- . . . . , . - - . .

E~' Ct~ (NaC1).it ~.-

10% steelin water containing 1 g. months of testina (Os < 3 pg -\ - ,

.s s.. ( . , . ., %.

e six !., ; 350 C after

, ~;.' ' . , '

kg'8 ). - .,,,'. * ' ' ' -

i~xO J ' , >

. x.Q y , w ._ g.e -.;;p, s* q'l . 4. . g

-gxy,._3-~ y~.s~

.

;

,,

',"

eU s 5 ~

. s*N :n,,

\.; f ~~ - c s.~. :_ ,

. .

J ; .,' 't*

,. [ - . .j L, ... '. ., ..*

71 -p --.r. ;*

~ ' ~~ [. .P. j f %. ../ <-}: . ,

. ~ . ., . - :.: q.

'

i. . ,

?.

, .

.

D '.f..% n" -[uv --r .-- .

. -

(. ;_.@m.y'% .4 y . -.-

:.', ** -

, '. , ..c; .

^ tf ,100F , u: q* C.- .

.-.. :.,.

,100p,

y , "..: .- ' . Q,,f ,i:-.

', ' 5e

'.7 j ~. ,,

j,'

w. .~.:, N.-.s . . * .

..c. . , , , A-- .

; ;%.... .% j; C%j. . :.r . .J ' - ~.f ,' ;*A - f, -.

-. .,.

|*

d after nine .: .. L. u .- . 't- ~/

<

FIGURE 2 -. Alloy ineonel 600 cracke. .. .

months of testingin 350 C water.e practically free

17%, Ni .

' 77% alloy in water containing 1 g.E-FIGURE 5 - Intergranular cracking of a CrCl- (Nacl), !5,

boundaries of the extra low carbon s.Iloy art of this article, theimental conditions ,-*

after six months of testing (exper -cf precipitate. In the second par- -..

ed. )

biluence of heat treatments will be discussOur research on stress corrosion crackingh r papers.s.esame as those in Figures 3 and 4 .(SCC) of high

!-

nickelalloysis the subject of our ot e (Fli;ure 5)in the 77%0 (Cr 15%.Ni

107, nickel alloy and intergranuhrNickel alloy and in commercial Inconei 60were revealed in' the 1S%osion test,

Wear ConteiningChlorideIt appeared us:ful to 4.Tect some stress corrature (350 C), with45,and 65% nickel do /, e

78%). Transgranular striationsnickel alloy.TLe alloys with 25,35,in deoxygenated water at high temqerdoys (chromium. nickel. iron)il as Nacl]. Conse-Clr.hloride additions (1 g.2-8 r chloride containingwater at @;not show any cracking.'

ickel content varying from 10After 6 m_o_qthLoLentrosioahTests performed in pure ohigh temperature,theretore, snow that tneining the occurrence andmckel content isquently, a series of austemtsc a

with 17% chromium and a n(0.5% permanent deforma:- Tto 77% (Tame 1) was tested. the predominant factor in de ermthe mode of stress corrosion m t eoint of view,the totality of ourunder stress applied by flexurelloyswith 10% and with77%

~. h se alloys.j

_ d in the a anc 4)in the alloys ;

l austenitic |..From the practica p i kel contentse-cac.ks.are transgranul.:r (1 igure: .I' Iesidts' points. o. ut.the c. interest in(chromium-nickel-ir6n')'with-ihterraediate n c" "d V 'YM -y't'y. . . ,

t>on). crteks a4 %--w~ g:.Q,1;g-- g . - . . .%'.s .

. .. .-%

- r'

^

'

. -~

+

-

(Ni35 to 45%).Role of Various: Parameters

g

with high'

The service conditions of austenitic alloystors involve severai,

*,

,

gnickel content in pressurized water reacthe influence of these

,,

well as that ut! : fi

parameters. It is important to de nefrom the practical point of view asb, l |$ r i13

we have determined t,,he,,,i,,,sg(extremelqunderstanding the phenomenon.9 2SE,

During recent studiesss: heat treatment (for examph*

.

played bv the foHowingvariable in the installations),,

nsitiution) c,cd,oIE!, "89cCr 17%, Ni

FICURE 3 Transgranutar cracking of ae

kg' ). those involving intergranuhr seencountered in steam generator~ (Nacl),'at

D *t**l in water containing 1 g . 2-8 Clb0 C after six months of testing (Os < 3 pg -other materials (often

!:

jr,ain,siize,and structure.~

s.-

- .

.

..;7*''''3*Nn uttapot.ited to 150 C.\'' 1150 . . . .

..' .." ..

I ..

Except as ctherwise indicated, these studies have b:en- mwm y,fgg~performed at 350 C in water with a very low oxyg,en ~-

- w - ~ M,W

content (0: < 3 ug ks<'a')V and whose initial resistivity is*.,

greater than 1 Mft cm. The autoclaves are made of ;50 p'18/10 stainless steel. .

,

Relarionship Cerween the Stress and- - - -

-

the Time to Failure FIGURE 7 - Initial surface condition: longitudinalThis relationship has been studied on inconel X 750,.- which has the same basic composition as inconel 600, but .

f a sppcimen before teg, _ _,. , __, . . , ,_section,' ~ ~

- ",

with additforis'orelements for~s~truttural hardening (Al,Ti, - - - -

Nb). Cylindrical test specimens ($ 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 Ejs,o c(3) N,,,_

j, p-= 80 kg mm-8.The composition of the alloy expressed in k W'.h- ~ ' , ~ ^ b

--- '- .'

-'

percent is given in Table 2. . EE'i Nished

*

~ J :.:.;u.. . . d :_. . ;. . n : .~

f* _

. .-

FIGURE 8 - Specimen cf inconel X 750 broken'

e c, w nu si s p. m n m

aher 2gso'

o.o. isa 72.s o.ia nas omos u i.co s.se os7o = 1.2E .2 -o

.b . s. .o5*..3, . - ,s.-

Experimental Method. The stress is applied in tension attached at one end to the p. ton and at the ot.ner to aisby means of the apparatus shown in Figure 6 and ed point sintated at the end of a thick perforated tubeconstructed entirely of 18/10 stainless steel.This apparatus which leads to the bottom of the autoclave. By action ofconsisted principally of a calibrated piston,provided with a the saturated steam, the piston exerts a tensile force whichcooled toric joint, and upon which the pressure from the is known by previous calibration. The diameter of thesaturated steam at the test temperature acts. An assembly exp sed part of each of the test specimens is chosen insuchof eitht specimens, fastened together with anchoring pieces a way that the test specimen undergoes the desired urnaxialand electrically insulated by oxidized Zircaloy 2 rings, is stress.

When a specimen fractures, a solitary finger of the-* * * " ".

:.- piston activates a microswitch which cuts off the heat to

the fumace of the autoclave. The reco ding of the,

2 -

% temperature curve allows the determination of the exact' time to failure of the specimen. After the autoclave is

opened, all of the samples are' examined by optical- ] - ymicroscopy. The cracked specimens, as well as the broken

' S - *. . - - M. .k. TI- -- SM ones, are withdrawn and replaced./ % . . .

TThis method of tensile straining with constant load is

, ,''

t r

h I,, 'h severe. la effect, when a crack starts to form, the uruaxsalstress incteases and this tends to accelerate the cracking.*

u,

The surface preparation of the specimens involved a,

H '< qj ' E finish machining (Figure 7) followed by ultrasonic cleaning* - %} ~ dj ,L of.the _ test specimens ~havg beenichosen in order to ob.tain -

~

M in a ternary mixture of acetone. alcohol. toluene. Diameters.

.- . c , : : (GG- , c.. . . , . ~ _ph :~a .y.. %- the. fo16vuig4pplieir stress'esi 0.4j 6.6,266.07172E.a ~ :

...

-| . ; m.-

; s 7 g ' d 350 C. (The precision of the diameter of the exposed partof the specimens involves an error of the calculated stress

I ! .

''

less than or equal to 19.)

~

r.

,

f [ Results. Fractures of the specimen (Figure 8) result* ***,

from a characteristic intergranular cracking (Figure 9). For*

| g |each stress level. the result has been obtained from 10 to 20

:- 3

,' ila test speicmens and the results are expressed as the length oftime necessary to cause rupture or cracling of a given, ,

- - -

percentage of the specimens (Table 3).We can, thus, draw a curve for each alloy, o = f (t), oFIGURE 6 - Autoclave with tensile stressing appa.

being the applied stress and t being the length of timeratus. Detail of specimen arrangement.;

!necessary to cr:ck 507e of the specimens (Figure 10).

.-

The time of failure increases significantly when the

istress tesel is lower, this factor being much more importantfor small applied stresses. For the range of stresses studied.

. WThe resistivity measured after opening the autoclaves when the indieste theI specimens have fractured ws: always on the order of 0.2 Mftem. the shape of the curve o = f (t) does not

threshold stress ineIbelow which crackingSEcitor's note - This shorthand nomenclature indicates the eMstem af 9

respective 0.2'" offset yictd stress at the indiested temperature would not occur for each civen aUov.

---

- - - - - . - - pa<jy.'Uf7W4 namcarrrunwrrrrrent_

Nickel base, nickel. chromium-iron alloys dit'fer from,

_ _s--w# [-3M- -W -

18/10 stainless steels by a smstler solubiliiy' of estbon in'._

''

j,*I","',1 -,

the sustenitic matrix: thus, carbides are frequently observed'7 *,, r - ', f

*

in industrist slioys.'' It has been previomly shown' that-,

J. ',

W 4, { $^ '4-

' , ' ' , ' . :. ' '.' an inconel 600 type alloy, with a very low carbon content''.

* *|,- (C = 0.002%), in pure water at 350 C shinn a smeeptibility. ,,, .. ~ . . -

'' f w' 'A ..- O

to stress cracking practically identies! in that of commercial, ,

ig , ~~ . , .,. . -# ' -

Inconel 600 siloy in the quench.annesled state. Electront'.f(.g: , t,)4*i .

. . .; . .

c * ..'

.0..,

microscopic examinstions show intergranular precipitations-

.'' ",,

d,,1,' * . ,6 . .''' O .. -:.g ,,. #*,; -

in the commercial alloys, wheress the grain boimdsries of , ..*

. J ;J. W .: *. y|&ld,.kg ~

-e - '. 4the low carbon alloy are free of carbide precipitates. As a7. --

.' complement to this study, it appested interesting to us to:'1.,' g ,g. + 7 ' 5.,'. Q* U examine the ocessional influence of certsin hest treat-

. f '. @t @ .. [, %.$. :i "*'. '.c Q. '

'

yMM) . . . , O*

ments, such as those of sensitization. -'.'/ ^ " 'C. :

' . |f ..Q '7 I ' , . ,, . s Operating Conditions. The materials studied include,

n-. ' ,

;f two industrial grsdes of Inconel 600 and an alloy of the', * ~ y~Q ' { y$;'Q,~7-Z . type Cr 17%, Ni 77% with a particularly low carbons ..M|.:n i"c e .+- '..

g&*|fY. V A J-Q.y;&, i 'tcontent. The compositions, expressed as percent, of these.t"".- .- 7 .- f

$s - ?.|- ' *.different alloys are given in Table 4.

.

Md.c -

.

.

v.yk.M|.,'2~. ;.7. . ,

:$.s R.;$*.,$%%'>.4-~ .C..' :*r'

,A_ 'ra.u e

__ _

-

--_ .o

FIGURE 9 - Intergranular aspect of cracking in * * '' " * * * ''

Inconel X 750 tensile stressed (a = 1.0 E !!.2 350 C) .. us2 iu m aio a.e em assee -after 510 hours in 350 C wattr.. . - een emo io m an am, u. ans, -

e. nm . .a s m . en see s om.

fAsu a ...

Test specimens (50 x 10 x 1.0 or I.T mm) were'=a-a ' 8- -

descaled in a hydrofluoric. nitric acid mixture in a manner.'~~ ' ' " ' * *

''*"'**"".'.'['"''*. to regularly eliminate about 10 ym of metal from each face..e. _ _... gThis descaling is performed either after water quenching oru es s, x ioos aos m m m before the sensitization treatment, when this is applied.

i.a s o a sso c io soo m rio zoo iso All of thgtest specimens then undergo an activstiontreatment in dilute hydrochloric acid followed by ause2me is seno eso aso ano ran

passivation treatment in nitric acid. A photomicrographo.e s o. no e is non sie sio ano taken of each lot after descaling indicated the absence ofas e o.a ssa c io meno isoa eio intergranular indentations on specimens so prepared.

The specimens sre stre'ssed in a horseshoe by cold" ''' * * '' '"

forming with the aid of a mandrel and a mold. Thespecimens are then inserted in a stirrup and mounted onsupports of the same grade of material. These assemblies, . -

,which are analogous to those in Figure 9 but withoutgsivanic coupling, are electrically insulated from the- . .p .....i . . . .i'.6

hu support assembly and from the autoclave by fritted alumina- -

pieces for. tests , performed in water.and .bg.6x-

Ziresloyfortesta performed in titliitin hy'drBxidel.- ge@*:

. - JJ -.'

7~=37. #;;.2 :.c M '' ac ,

, , _.,_. y . u . _-- .*e.:- '' S -The maximum stress of the externs! fiber at 20 C,g ,, .

evaluated by strength of materisi calcuistions and byo .,

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

i""

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

The ' starting values of the yield stress E .2 for the0~

:t various grades are given in Table 5.ROo , . . .i . i...i. . . . TABLES3. e oos seeso

evera a.aar everwee ou nssu*a'*o= i *. .. aEo,2 et 20 C in

kg . mm-2

A = Inconei 6o0 40FIGURE 10 - Relationship between the appliedstress and time until 50% of the specimens Siled in B - ineonel 6o0 24water at 350 C. (Note: X axis = time,in hours, beforefracture )r cracking: % axis = applied stressi. C = Alloy 17/77 23

.| 1152

I corresponds to an industrial treatment off incomplere '. e 7 - Q "", % '. C' / tL "

,- .

.o . , j. s s .' jI

mlubihty cf the carbides; (2) the quenched conditinn *,

g ** I e/ , , h .,e' a.O o,

which is obtairad by a complere solubility of carbides with ).i*

,, . ,

* 4,\ p hthe appropriate heat treatment, holding fr:m one to two * -

T ;: 4*. '. *fI bours at 1100 C followed by water quench; and (3) i *

,

' n ,, .| sensitired condition cNracterized by precipitstion of car. . , " W ,6'~ -** i * * ' . -

".gg , , , ,

j bides principsily at prair. boundsries after s treatment of *' y %,, f,- 7g s ..

one hour at 700 C followed by quenching in helium gas. '' * *. - w g* .)* , .'I For the specimens treated above, tensile tests and

' '8

''* -

g "* ' . ' , . .| electron microscope examinations were performed. Table 6*'* ' *,g J . . * *

,. .,

'; ' p . $.I summarizes the characteristics of the Nudied alloys. pi *

1 -- ResultseThe ' proportion oFeracked specimens, as well 1'e hv., -.

-- O *- =6 ~ % -2* 1 '

t[ J'as the elapsed time before cracking,are gathered in Table 7. g .,"

F J, ,/,, 5 pr'

.. - 1= .es .

-..,

% i -. ;..#a A. e . , _.-_ f. .f ; ,g . _ . . . ..

., ,,,_

. . . . .. ,,

-. .. . . .. - ,,

;'"C" =. FIGURE 11 - Alloy A (Inconel 600) electron.. . . ..microscopic examinations. A1 = as received condi.

. . . .

. . . '. , tion.. ,.

. .. . _~

.~ : .. . . .- =. -

.

'

* ,' _..: m. . . .. c_.c. . . . q- . . - . .. .. .

-. .. . . . _ ., ~ .; ;.*: ; ?: ?: .%'

. ?:'.'.'.T."'..- =. .-

.. . ,....y;.4 .. .. . .- . .. * r ...r;. . .. ...

.

&*g*y'.c').' *- . . . ..

.. . Wr,

. . ..;- .

'

. * . . .

. . , . _ , . _.,,

,.

, * ...q--

: t*.'=. =|. * ;' ~ "' * -. .

,

* - ~,,, w , ,,, _ ~ ,; ,,, ...

, , , , , ,

,.@ y,.; . .n - *

,

f'

, , - - }.., . " * * *" = " " ,. . .,,

- -.~.. ' .:i ...*; = - - - - -a. ..

' '= = = = = 0, : : . . = . . - .,.

' -- -

- .. .

== = :: = = =.

5 N --. = = = = = =" -- .. . . .

,

' *

..

,.3 - .;'.*

-. . ..,.

The following points are concluded from these tests:- (a) All of the alloys tested in the as. received state were

susceptible to intergranular cracking, although the appear. FIGURE 12 - Alloy A (Inconel 600) electronmicroscop,c examinations. A2 = Quenchrd in water,

: ance and distribution of carbides were very different from i

M : . . ._ on,e all,oy. to_ another;;(b);the. same . alloys. tested in the . - 89" 2 hour t3:_tment atj,100 p. _. . _. u,. , _

-s& quenched 3 tate- afso.-were suscepiible toEintergidiiulirkif * ''T-% E E- W3._. :NP w mr~

M - .m.~_

.

f cracking. This treatment resulted in the complete solution ,tited in .the grain boundaries as is shown in Figure 18.Thei of carbides and the absence of carbidesin grain boundaries; susceptibility of this alloy to stress corrosion is, therefore,I and (c) a sensitization treatment effected from the as. practically the same vehstever its heat treat nent.

received stite'ToF~the two gradis of Inconel 600 retarded _-

stress ersekine. In effect, under our operating conditions /n//uence o/ Coupling with Other Me arsand after 10,000 hours of testing.no cracking was observed A study has been made on the influence of couplingat allin these specimens. with mild steel. with stainless steel (Cr IS%/Ni 10%/C <

|This behavioral difference is especially remarkable for 0.03%), with gold and with platinum. on the stress

specimen A (Inconel 600). Cracks of samples in the corrosion of Inconel 600 slloys (grades A and B) and'

as-received condition were repeatedly observed after 1500 inconel X 750 whose composition expressed in percent is- hours of testing whereas in the sensitized condition no given in Table S. This alloy has a yield stress Eo.a 20 C =

intergranular cracking at all was observed. 84 kg mm-2,On the other handcfor alloy C: Cr 17%/Ni 77','c.with a The specimens were tested in the as. received condition

particularly low carbon content, (0.002%). and with a (see Table 6) and descaled in a hydrofluoric. nitric mediumsensitization treatment of 700 C, no carbides were precipi. (thickness r mov-d: 10 pm).

!!53

<

.

, . . , - , . gf .4 ,,g*'- -- . .-. .-

,.

4 ,- * * * e.. . . . .. ..

4 %#-.o - . '* s - , , -

?' . .o '7c ~* *.. .

k' , * h.

'.? .f= .

,. , ,,'+ ~;;~ - -s .s . ,-

. .

_ - c -.* , . ,. - .

* **

-.- W.. . . . .=, \ - . = :. .:. 'u :n.'. ,s ,.. ~ . - :.,+...-::. . _ - gJ. .. .

...#f.-- . . - e . .. 6, ; \ .-s. -

. . o;y. 4-- g..

. -a .. ~

. .,

?.-~ _ ---- . =r .f-: .- s . .

-z. .:* *

, 4,, . -.. ,1- f . , ' i.. . .

., .. *

i q. . .. - ~ ' . -

.. ;. -, ,

e, .w.ge - . . .; .-

.,- .: .---

,,g #e . .- e *. . ..

, . * * . 5' p *../ .*

,- -. .. - -.; 5.9.. . g :. .y . .. : . ..... . .. ,;- - *

*

. . ..

2, . . ..

,i...r.. . .

' **p g . . g ? g ,' ,s 52 . - + , - .. . ; ;-- - - - ~ * * v' " ,' '- > %'.s -: 4,, 3 .- . w - . .1,' . p . . _ . . g ,, .': . % => ~ *-

,

... - :::.

FIGURE 13 - Alloy A (inconel 600) electron FIGURE 15 - Alloy B (inconel 600) electronmicroscopic examinations. A3 = Sensitized condition microscopic examinations. 82 = Ouenched in water(one hour at 700 C). after 2 hour treatment at 1100 C.

.

-.

_.

-

-..

..

. .. - ... . - , * w , , , y , .e w , - - . ... . . ._

. . . . .. ..-| .; -. ,- - . '; , .~ . . ,.%

- . ...*s

S.'..~g .5

-

r.a,-

.e =

- . ~ . , * -- ...

:. u . : .C. ' ,h. .:p- .h.....

..r ,, L ,m,..' ., . . U . .;; - . e. ---- .-

c' %.:

,,

'.. ( ' . |.| <r; ~ ~.. .. k' f.~. f.s .

*

;-?<:. .. . t :.

-

.t. . - ., ' ~.. -. .- u:.: : ...t . 1 .. - -

..

, . ..

. ,, . . ,,4 : . .. ...,

. . s; ~ 4. . , ..

.-

.

.- ,

-. . . : . . . . ,. T.. -- . w..

. : ,.,-.* , . . .

; ... , ., s. v . >-

.. . - . -. e. , y . _; - , -e .. ..%. - .--= .*

...

. ' , . . . s. s. -1 :.w- . ,. . ..n .-

.

, A.* w.-- . .

e. s %. -

-r ... .. . * 7 ,, .

..

.', ', '':. % , ..,'. ,-

.' . S :. .r . .t'-.';* . ,.. .,.w.*.r- %* . ,.,. . ..

.,-, a 2 .< .,g .v e..y;.

-,

' . . *-,:,. , . [ . . ~ . , ,y .. .. .

' , . ., . . s .-- . . .. ,p .,

L . t. . . ' , , -' '

s- - . ' . ..r'.. . . -

J'. * -

. *.. .- : ~. . < - p 9 ,

,. - *-

n .-

. . . , ,...

.~y.- ,....

' . - .r- ; s.

- * 1. ..,.. )' ..%*' # .

.

\ ~:. . . /.. s 5y.: y. z' . " 5 y .

,'

<,J~-* - -

-.. -

.... ,. . . s,. .'-

. . -.

..-

,'- }9,. .. .

/*L-.

,,

' ~ * .t ', y -*-,.. ,

, - *. .. , s.e ... ..

-

..a. . ..- --- w . ,- ,w c- ,.. . .- :u -; :- c.- : . . .

. -- . . . . . - s .;.

. _ ,,, _-... . . ....-.. .n: .. .-

'.:--- - - bFIGURE':-14+VA11oV3 B' (Incon.el-600F*eTectron . ..microscopic examinations. B3 = Sensitized conditionFIGURE.--16 eAllop%-(incone'l' 600): electron r.:89

microscopic examinations. B1 =~ as ' received condi.tion. (one hour at 700 C).

4

.

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 inconelas illustrated in Figure 19. The stirrup and the holding 600 (EN2 = 40 kg mm-2) indicates that coupling withscrew are, moreover, made of inconel 600 in order to gold leads to the absence of cracking for the conditions andeliminate s!! parasitic effects. for the time considered.

These tests were carried out in demineralized water. Coupling of this alloy with stainless steel seems to havewhose initial resistivity was greater than 1 MD.cm, and in a slightly unfavorable intluence, but this is not very clearsolutions of lithium hydroxife whose pH was 10.5 a,nd . under our conditions.11.5. These various solutions were deoxygenated (O. < 3 In lithium hydroxide at pH = 11.5, the effect due topg . kg-' ). coupling does not seem to be detectable. This medium

At each opening of the autoclaves for examining the exercises a retarding aetion on eracking.After 12,000 hou.s of testingin water 350 C,we note a

specimens, the resistivity of the water was on the order of g'r;t' j 9 influence of coupling grade B Ineonel 600 and0.2 MG.cm. The variation of pH in the lithium hydroxide ' .

solutions never went beyond 0.5 pHunits. Inconel X 750 with mild steel.The same conclusion cannot<.

E $0i

r \. v v .. . . .,u, v . g%. .

. .- .. .. . . syn .. ,': . . . . ..n .. ....s..... ...

... . .

....

.~.,,,v...,s...

.. . . . .. .,. s..

.

.. . .

.. .

. , . . . .; ..

, ... -;::.;-2 ~. -

,c . , , . ,.;i]-

.i . ., .4 _ . . .os . s .. - - _... . .

. .... . ,

tn. . . . - -. .y . - -

j;.,. ... . .- ..

. ,

r i- -: . .s, ,,e. ._

.. '

.,. . . ..

,

P .. N '.1.

. ?. ~ .' ., . si ' i. .

- -

p- ... .: . ~ . - -.

.

. . . - ,s vs.

.. ..

; .)tr. s - -.

. - . tL ;,en ~g. g. -.

. . ~%y:' . . . ,,.

: ~~.. ..;:,..~.*m.: w . 5 V. . .. ,. . . -- ; p .- .

, ,- - - - :.-~ .- , .-:s. \ y v . - ~ a . ... .

-

: .

... . - . . -. , . t

%.: .L,..~ ~e~ .. .n

. . . , . ., ;. e .. i

- : ~ < . ','

.g. .a c.<

5.'.-4 f,p

n ... .. .4.- . s . - -

.D'i.b~ .|, b ~ . ,#.3 ', . |* . ..? $ , , -- -

' ' . - I 5 1. 'e

C b .. ;f,'.jh--

..

..LM,.

s,. "FIGURE 17 - Alloy C (Cr 17%, Mi 77%, C O.002%) 4 .: 5 7

,

1electron microscopic examinations. C2 = as rece;ved ~.

Y k~.r.. . . :-- .6 . . in.-':.- *:5*/condition. -

.. .

; .;. . ;_ . .- . .. -. 3.

~- --

. ... .: :.mp..;..;ye >--

o,..,..... - . . . .

. . . . . . . , . . . , ,y. ...g.. . . . , , . . , , , . . .

..;. .... . . .

. . '., '

FIGURE 19 - Horseshoe apparatus. Sample of''

inconel 600 (interior) coupled to gold (exterior)'' * .-

1- without crevice effect.- * <.

.-

?. .. .. .

.. _

. . .. . -

.;. .-- .,

.

* %- :*

'

..

K ,. ... c- -

,,ea ,

, _ - . _ -. s!,, . , , , , ,. ,.

sr .* . me e t.o.. me e. . s

. 3- .-T- 9 e ese a mes m. a.m. 9,es a.s. pse em a.m. taas,.- * ,g , ,

. * nou._mW u.u e4B 3Was ergs .Q.

* ~ *n . .e.,= s,,e me' ene . ine ..

- .--. .

.* d s -. er, err ene ene

.

5p '_

'-s i

- --

N.

-

_,.,,,

TABt.E 10- -

'f.

!.... ' uneoa.e soo carmeones to Auey a 6n Tebse 14)*

.V..'4af:.E.'. L..L. .- *-: - .

,.

t . 2.s . ...s.~..'

Number of 5emp&as Crocked

After 12.000 Hoews'***"""d* *

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

electron microscopic examinations. C3 = Sensitized Water I.iOH et pH * 10.5condition (one hour at 700 C).

1.r.1 Mad 3 , E '' "&~ ''' '' '~

~'~~"'i''.y;)....c.. . . . . ".-h n- ', ''3 ' $ .:_ -" '~~ M ~__ Q ., ---r .. . 2"' "# * 2 --

. --- - TABl.EB'D' ~- ' '0/9 ? '" '' dx 750 '' ' ' 0/9 '' "~ ~ '

i

(Compositions Espressed in Percent)Inconel600 019 0/9

| coupied to goldC Cs Ni Mn 5 Fe Al Ti Incenel X 750 0/9 0.9

0.05 14.7 70.9 0.10 0.05 6.20 n.66 1.96 go,,,,d 600 0/9 019

coupled to pietinumlacond X 750 0/9 0/9

.

be made from Inconel 600 coupled with 18/10 stainless Incoad 600 in0 0/9***'d''18"O

steel. m. nim mdancon 6 x 750 0/9 0/9

influence of Grain Size (incoad 600 4n0 y' 2noSome tests were performed On Inconel 600 specimenswith a relatively large grain size (between 200 and 300 un). **f'd '* "'"These specimens were descaled in 'he hydrofluoric nitric ineonei x 750 6no 0/9

acid medium (thickness removed: 10 pm).

1155.

- ____ _ _ _ _ _ _ . _ _ _

_ w.-- . p , ' :. ; y y,...-

* --

v > ., .: .2'' ..

.,

.s\.1 iq-

r. ..

M = ( ]~

. . m

\ * .q % %'-

,

.a ' ,: '. .

,

4 .g'> .i-

s og ..a ;#'.q . .

,

.g . , - . .- p .,

t*

-E . . . . - - . _ =:a yg ' :. : _m .-

. . .. - . .. _. 'V p: s d. 3

~

'~

\ ? /'*-*

. ..

\- r.r. p \ .--

.. ,

. x . .''

c .... Q . *

. .

\*,a- .- .

--

{ !.' . . ~1 .P 'f9 N T". /*

'i' " -. ,.

s .- *

.' '' ^~

. iU M ' . " - .!*.t., "J s> .C3 $ '. .. ,

*-..

. . . . . . . * % . . e . . . .. .a ~

7

-

., F '.D ,50 p, ..~~

~

w

* . V~ . ~hf .d A e p., .

.. .# .,FIGUFsE 20 - Intergranular cracks (paths AB and ' p' .

*

..

'.15 I PCD) obtained in inconel 600 with very large grains. .' -

;, ;" " , ' . ,, ,., J * f.h{ ,, '-.

i. i . d *AB polish with diamond paste; micrographic attack .-(aqua regia and glycerin); CD polish with diamond

, , ,,

paste. , ';.

FIGURE 22 - Tensile specimen (a = 2/3 Eo.2 300g.g e -- U W y.;.;- p m y s s +-- e - C) after 2,000 hours in 350 C deoxygenated water.

,~*' ' ' intergranular nature of the crack.- .

. I_ .,

: e . ... ~. . .. .-

.

;) . l' ' '._

'-

. . , . . . e-.r w *?. s .

' ,w 'p'

i., j . ..

..-

j.

,

y, ;i,

4/ .g

-

(e - N . ,. % . ., ' , . . * , _ . . . .

.* .- J.

. /. . ~~~ , ,., .- ,~ . ( L - * -* '-

,5 ,_,

/ ,

< e- . ..

... . . .**' : |50 p '.. - ~ *- -'^-

.

. .,. . . ..

>. g. .. . .. . .c, . . -.

.

% .. Li * y -..

,,.

FIGURE 21 - Example of intragranular cracks. b. ' .%. .,.'

j/ -

. w-. .. .-.

-,

s, f'J r s ?.

s - - . _ ,-

,i

. .- . * * -~ g .

.

After twelve months in rmre water at 350 C main. [ r.: , ., ,

,, , tained at constant conditions, with a, bending stress (0.5%,. .

.. J ,. . _ .. .M. . , j.,

*-* cold ' permanent deformatio'n). rmi' roscop'ic. exaininatios,.i "' +:[-~ ' g2003'? " N - jf{b| gMg,T ~~,, ;. .;,. ... ,

c .,1 - ''' F- SEf2:

reveals a characteristic intergranular cracking (Figure 20). * ~~' ' (2st;..,' -

.,

This phenomeno is, therfo e, guite comparable to that C h a. 7~m | ,..,

ebserved for the usual allov whose crain size is venerativ on *,

the crder of 20 to 40 um. *

-

However, under our particular conditions, we note theappearance of a few rare cracks of an intragranular nature FIGU,RE 23 - Bend specimen (Eo.2 300 C = 86 kg .

-

but which do not go beyond the perimeter of the grain for mm I after 2.000 hours in 300 C deoxygenatedthe time of our test (Figure 21), water. (a) Fracture zone of the sample; (b) example

of intergranular crackmg m the middle of the bent

influence of the Structure' 'reg on of the specimen.

After a complete aging heat treatment, Inconel X 750attains a yield stress of about 80 to 90 kg mm' by -

precipitation of intermetallic compouads. It is, therefore, Some specimens of this alloy have been tested underpossible to vary the structure and the resulting mechanical the same conditions as before either in flexure or inproperties from the solution treated condition (yield stress tension, in deoxygensted water at 300 and 350 C. The35 kg . mm-2) to complete precipitation (maximum surfaces preparations are identical to those used for thehardness). other cases described above.

. ssu.

. ..

k-|$:d:T'% M q-:ie; ; , 'G y,~.; y% .,: y.

1.

A.

)ea ---.

.

_j ,. .s .,

* - q '. . c. &,f.:,, '',

se 4- -- e .- 4.-.-. e4.< . .

^ .

.-e- ( M .h .~; Q-*

h %n..;1. @b . 9

v,. $ S>'.taN p, , .

g -q;'.!;-- .

4, . . ..? s ..j e ,.;. ;,25p, . . , e

. , - . . g_ p, . _ . ;;. 7 _.. _. = - . ..-. .--.

.r..c.~ . . ._. . .u.. :. .. . ..

k,h

- -- %d ,gg/ - er.d$.;, g-y e , ,

'- - Mr M. .. V1'..,

|

. ; h,@,',n|:[f. ; [ . . , - uFIGURE 24 - Intergranular crocking of a bend ., ,

,% ispecimen (Eo.a 300 C = G8'ing - mm-a) after 2,000- <j g,% . .hours of testingin 300 C deoxyymated wstar. ,

,1 %)% g %a . . % WQM;..*

.- -

;- J. . C-i'{;T i :.

Q,Gf j..-}.

The following resulted: (a) Tensile specimens stressed. -',

!

were all broken, by .an inntgranular process after 2,000 . h. .25h..Lto 2/3,3/4, and 1 Eo.2*300 C,with or without notches, J-s '

.

hours of testing-at 300 C for theaHoy heat treated to the'

strength of 86 kg .. mm-8 (Fipre 22). Specimens withlower mechanical properties (68 kg mm-2) did not crack FIGURE 25 - Intergranular ast.eet of cracking

after 6,000 hours of testing;(b) Bad specimens (0.5% cold unconel 600 type alloy).,

permanent deformstion) underwent intergranular cracking .

after 2,000 hours at 300 and 350C,whether the metal washeat treated to 86 or 68 kg - mm-a). However, this faueT].$ .7*' W D %cracking was clearly more severe for the alloy with higher P l<.%.

'*-

,

p~'t - M 9 4 [ 'g %, 9 [, g N

4-mechanical properties (Figures 23 and 24); and (c) Some

.

T_ 7 .qb Q3bend specimens, made from sheet material which was- ,g

J

"U;. " D km./

quenched after solution treatment (yield stress-35 kg . *{' ;,, y / 4N-'-'"

'mm-a), did not show any crackmg. These tests went Ypg4 ^ 3 ,-: 'beyond 8,000 hours at 350 C. p- . ;

. g ., dg N9These results confirm that Inconel X 750, in the a'Lf'~'* O.Z, . JW 9 .y"

hardened state, has a susceptibDity to intergranular stias . . - ..-

P Pd-g [ / k,f.'i; XNi.?h.h'

cracking much more severe than the homogeneous Inconel*-,

I'

600 alloy. Furthermore, the role of the structure factor is|

I .'" ? Y~ ''r% .:

i % f'Z M (Q [W ibinoted since the suscep'ibility is greatly low: red when the -

intermeta"ic precipitates are decreased in number and the' ath. A .3 .'.~ :. . .; > p # ", f df.tp.jv6.'resulting mechanical properties decreased. In the extreme 's

? ~ p.g,8 -~

-

case, inconel X 750, in the quench after solution annealing--

condition, seems to behave sirmlarly to inconel 600. %Q-5.".9 s i g (,d3 .4 - .J . ;

- *+

Observations on the Cracking Process- " , ,t- * i7-/, !. % +, ;i''r-, 3 -1| - Role of Sulfur

- '-

I .

?:f-h.Q.-y?. -

h.bY'-''4e:.!QjSCRi-g:.,f.4.,,f,& '3. $1?I5-Y - -

exammation and

'- ~ _ ~

Scanning electron rmeroscopic . , . , ,

f. ,,';,Q{-g ,7, ..' Ny,;.3,,4, i

j-

,

analysis of the emitted X. rays bear on the intergranular , So p'. ;

g t y,'cracking process for the alloys studied. I-( ,' ,

I'The samples examined were cracked under stress at 350

C la demineralized water (O < 3 pg kg'.8). Inconel 600*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

testing. Inconel X 750 in bar form was tensile tested (0.6 Ecracking and brutal ductile transgranular fracture.Onconel 600 type alloy).

0.2 350 C). Fracture cccurred after 800 hours of testing.The following points are made from the test: (a)-' * .

Microfractography confirms the microscept observationthat the ctackingis intergranular in nature (Figure 25).This presence of numerous crystalline precipitates at the grain

cracking is then transformed into an aspect of brutal surface is noted. These precipitates are dispersed or in j

fracture of a ductile transgranular type (Figure 26);(b)in aggreptes in platelet or rod-like form (Figures 27 and 28);'

the propagation zone of the intergranular crack, the (c) these precipitates have a tendency to be more abundant

1157

*- ,

2g A. S ,,C.a .Mp@gS *ot s MFe=wysyn!= pre--

.

.s .. - . L r, sm :W~i.,''=did jh. .;q$jjz..:-v~.,,

. i'.* 4 : W,7# Q,J - N,7 C*'

?a:* '.

*,.,y %.n 1,

-q., 2: .. .. " - -,

rr ,... . - . [ Q.,, . l' ( '..Y., p,s;d.. M.

Wi - -).?']' . ' . .- :3 ns -. . t .s :-

. . . . . . ,:......_. .. g.

.

- , . . . * * .9a.,

. .. . ., < |%u +,e. .te A. , ik" . . :

.~ c . .;. < . . .. s. n=.= =mm:m. a . . h 4-w -

I- ; w. . . x ..~. m.: _ . ,w -

-

, .=w. = m.t -s =.=. m. . -..

.

---

..

4a..!,A. ; p;;; ;;.i.i .I I.

.. x -5.f .

a-t.. , ,9, m .- ef,.w 3 .: - ... ..

%, , m . c.; a. yody. r.7 3..;%,.g. . ~= _ m .. . #% .... . _: .

n. .- -t .- .m

., :~.. ,:-

.

,v ._ w-

. u <-c.

--- -

#e4 ' ' . .. .4

,s * ?y . s - ,. ( f,.Y. ** *

.. . a.m

{ %,, . pea, gW^,- . . y.? " FIGURE 29 - X. ray emission spectrographs. Precipi.,..e.Q tates: a = aluminum; b = sulfur; c = titanium; d =,

,; g,, 'T- e chromium; e = iron; f = nickel.'- '

. h ' .* i.N '. '..,$.1 . , ?&'

. . . . . - . .

. [+~ ' Y ,, , k, .M * . '.

' ' precipitates reveal that they a'e very rich in sulfur,- * - cr. ;_

* *.

f. ~ ~ Og'(,. M, 7-. ! h frequently in nickel (Figure 29), and that they can also, . / j Q .4.

*kO# .b contain some ison. The X-ray image, compared to the.? '~ 4. p4

..

4 '._' 7',t. electronic image, confirms this point very well(Figure 30).

,

f gs' -

According to our observations, tt seems possible that 3,

g y yf.'pi.a* -..f . q ,- - .-

* v %.L 3*J L intergranular cracking of the alloys rich in nickel such as- *.

,

I.nconel 600 or Inconel X 750, is related to the presence ofsulfur containing compounds in the metal.We can make the

FIGURE 27 - Precipitates at grain surfaces on flanks comparison with the properties of nickel, even high purityof the crack (inconel X 750). nickel, that is embrittled at train boundaries by segreestion

of manganese a'nd nickelsulfides, this occurrine for s mifur. .. content as low as 0.0009% '' in the alloys containing 75 to} l

*

7Wo ruckel such a segregation is thought to occur.These fgkF [ ,

..J(N ' M.' compounds, which are probably unstable in water at 350 C, .@- t

t c q ,},-[-iggN .44 , Q(?[g,

f R _,. Jead to the formation of a :trongly sulfurous medium in i .f. uthe small metal volume at the ' ottom of the crack. This \'" o-

% region would then be favorable to a rapid point by point ME , ', A e'-Y. c

dissolution of the nickel rich alloy. Precipitates found on4 J*e ~.

the flanks of the crack would be products of this reaction. I

A'sb%N~h' '^

. .. -

Q' t;p .-;.i e This mechanism would explain that the observed IN'~%-id -

c., phenomenon is rather specific to alloys with a high nickel %Y 4.;.S ,y .//.' M- content; therefore, if the concentration of this element was i'""%/b * *-

k ,N w -4' ' '

',y. lowered, the process would not occur. -

.<

Furthermore, since the nature of the sulfur compoundsl j@ .'[ kpf and their distribution in the alloys are not controlled great _f pw

,

q ,". Q. J,ff f'

7, . , J .',.

J 9. %differences should be produced by different melting and MTf-

'[ ,.9 (* $-

.#] fabrication techniques. This would explain the apparent,? .-.. f

divergencies observed between different batches with the)-

'-

.* .# 1 ' 5- same nominal composition. --

k NM d. . NN,,n.' E . d C : N:G .A 'Y N # $<.' N.M.- O: -- S'_.~.L-D8b.- -. a

- .- g --- :.- - Conclusionsk Y=b . .~-. , my ,. w- . :.if r..

- ,. >

,e - .-.

'Different service conditions for " nickel-chromium-) i

--

.. 3

-i T , iron" austenitic alloys with high nickel content, such as,,

[g% 'M ]< j. w, .g.r.n..-h k'-influence on the susceptibility to intergranular fracture of

*..

Inconel 600 and "X 750 type alloys, exert an important-- ~ --

these materists in water at 350 C. The following points are*

made:FIGURE 28 - Precipitates at grain surfaces or flanks 1. The time to failure of inconel X 750 increasesof the crack (inconel X 750). sharply when the stress decreases. However, it dees nct

appear from our tests that there is a threshold stress belowwhich the phenomenon is not produced. Cracking has besnr

in the zones near the lip of the crack.They become rare in observed for a value as low as 0.4 Eo.s 350 C.the neighborhood of the propagation zone and are non. 2. Certain hest treatments enn strongly influence theexistent in the zone of brutal frseture. They are not behavior of incone1600.We have shown that s sensitizctionobserved except in a few rare cases on the external surfaces at 700 C, shtaugn producing an intergranular precipitation

of the ssmples; and (d) analysis by emitted X.rsys of the of carbide notably slows down the cracking process.

!!58.,

' -

@ p(T ,/ wauer ad 350 C. howser, the appearance of some intra.- g '

"~ *

granular cracks was noted on certain large grains..[g - e o.

b '. 5. The influence of the structure has been shown$'[[\ D.Id , * k '[-l )*

-

on alloy Inconel X 750. The susceptibility to stress.

& 4 ?"'; 4 \ ' }# t. 5 cntrosion decreases greatly if the intermetallic precipitates'

/ 'e M * g '. 9 ,. Q become less numerous and the resulting mechanical. .. (' '[ ., y -t properties decrease..* ,

w.,~

/ ft. 6. A mechanism is proposed and related to the'-

@ b . h. ' .-

[ @^,-. p,p

W''m ' " , - W. presence of sulfur conlaining compaundsin the metal.Thiscan explain certain of the observed phenomena.

.~.# .. k ;. .1.,

' ' eg.gf' Y N. ,~ '.'.r. # 66. . Thus.. the complexity of.; industrial installat. ions.-in ' ;.;.-',**

..:~~ evitably leads to the simultaneous ntervention of numerousg. [, ( 3 parameters whose interactions can be contradictory. Conse.

**

,

f, .< > d. . .,6 ."w:'. -f.: . , d'*

' 91quently, the real service behavior of ineonel 600 and X 750

- ?O W ". . A.4

e. * .. .4 type alloy will be separently cuite variable:it is.therefore,p ."w.; a c.( '. ~h . c.. . -)3- J. wise to adoct the createst prudence in their application. *E.--d. -.

b 4.s. g" I ''

< ,

.3 g.g -;

Acknowledgments5p 1. , , ., .i .

( tyh3 I#We would like to thank Madame Meny and Mr. Olivier -

. . . [7 ^ hjii r 'g ViW.s . for the scanning electron microscopic examinations.+

.

l '* rA ' / -tc:;._, , . _ , , . , , ,

' W References3 . W - W 3 .;* R.:dqn:. m@ q %p . -<

, . ..p: ':1.--my. .* . -? .'

re;- ~.x.:: . :.Q.

Gas, ~.n a .9:sc.?

[Qi,/...Oh_h.d contrainte de l'inconel dans 1 eau 'a haute temperature. 3 cme1. H. Coriou, L Grau. Y. Le Gan, and S. Vettier. Corrosion sousP c . WO., J.:Ae .: ,. . .

5 .h$h.Ct .' N, . 7 .:., N. ) *T. ** dh'-[M" WMU:..:.;h@74

,

..Z. Colloque de metallurgie sur la corrosion.Saclay. North Holland, .

[. [ amp. Publishing Co Amsterdam,p. 161 169 (1959)...

E 7..$3 2. H. Coriou, L Grama. M. Petras, and S. Vettier. Fissurat. ion sous. &. .w '., ,.s; de. t ,- m. e-

. . *...:.. -e

K '.' *;.p,% -;.y - d u.. ,4 contrainte en milieu chlorure. et dans 1 eau pure a hautes *

' *%g ; ~.Qfys.4. *i ef .|

y: *@~ 9'-D M.tc -' temperature d'alliares inoxydables au nicket Communication=f 5- .

.

...J. .- .-W,.fi | ~r b$W'd|d. ,>;:..<.S'c.d ],.

, . prisentee au Colloque de la Socie'ie' Europe *enne d'EnergieiJ *. .

. Atomique, Studsvick. May 22 23, (1962).b

[* ,. W; 4 a ,,,f: - '~ ~.9. T -

- 3. H. Coric;., L Grsu, C. Mahieu. and M. Petras. Sensitivity to .-

[ ." ;. 1*.'

.'A' [+

~' stress corrosion and intergranular attack of high nicke!~~

. .

- o.7F: .k1 A ]M '. austenitic alloys. Corrosien, Vol. 22, p. 280 290 (1966).

fe/ , *,' ' - ' I.' * _.

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

*[ . . ,, n,-

f , '. -;, "^

'*7?' . . . . , .4 resistant to stress corrosion cracking of Ni-Cr Atloy 600 in@ S-/ r . n 73 , , . ."~N.

'

pressurized water. Corrosion, Vol. 21, p.1 8 (1966).,

, 7;~3 5. G. G. Foster and J. W. Taylor. Stress assisted corrosion of,

( ~ ;4 I.. .t" [k [ *

t,-

. b4 " .g 'i- w .1 ;;y .'* Inconel 600 heat exchanger tubing in high temperature water." ' ' ~ " -

i'9. 5 .* & * '. Institution of Civil Engineers. Conference " Effects of environ-

Ei ' ' "- , . * M... .$|C% 'k ". 2 ''

), ,. . ' .? d%$eJ.h ;..-4 ment on materials properties in nuclear systems",landon, July

.*

jf. ,f y ,.'' l '. '.7 ' 4 h .c "# 1-2,!971.-

i ;j W; :. - ,..yi'_. :14 .. . . . . ,) 6. R. M. Rentler and I. H. Weiinsky. Effect of HNOa-NF pickling.

* - ' Nt.. w on nress corrosiory cracking of NiCr-Fe Alloy 600 in high .[:-W"qf ;, , . .c ,a..._. ...

'"". " ~ ' '' ~ * ~'EW punty water at 600 F. WAPD.TM 944 (1970) October.1. H. Coriou. L Grall P. Olivier, and H. Willermoz. Influence of- carbon .and nickel content on stress corrosion cracking of-

- . - -

FIGURE 730r- Electronic imagesilatieve) andiX rays ~, '""Q' .'S i'2minenities'tainless'anoytin pure.or.chlorinaiad. mater'ss.35n r. - er--.. . ._,..,.: g g -. ,- M.V . .-s. ., :iroceedings "of,Conferen'ee "Fundamehtal AspectE of SEe6T.c -+

(below) from the same zone of the crack, showing the Corrosion Crackir's". Columbus,1967. Ohio State University,association of sulfur with the precipitates Oneonel X NACE (1969).750). 8. H. Coriou and L Grau. Stress corrosion cracking of high nickel

austenitic alloys. Nato Conference on the theory of stress

3. The important role played by certain galvanic 9:rrosion cracking in alloys. Lisbon. Nato. Brussels (1971)..

effects have likewise been showr.. Contact with a noble9. G. Boisde H. Coriou. L Grall, and R. Mahut. Intergranular

5"'55 **" 'i n cracking f inc nel x 750 in pressurized watermetal, such as gold, exerts a protective effect: contact with

. at 300 C. N ACE. Annual Meeting. Chicago t1971) March.carbon steel leads to a strong accelerstion of the cracking 10. W. Hubner. B. Johansson, and M. Pourbaix. Studies of theprocess. on the contrary.18/10 sta. less steel may have a tendency of intergranular siress corrosion cracking of susteniticin

slightly unfavorable influence. However. it is recalled that i,,.cr.Ni alloys m high purity water at 300 C. Report AE 437, .

the influence of these various couplings has been deter. Aktiebolaget Atomenergi. Siudnik. Nykoping. Sweden (1972).mined in the absence of crevice effects.These effects can 11. H. Coriou and L Gr211..Proldmes posis par b corrosion sous

perturb the cracking ph nomenon, occasionally accelerating contramie des seiers ei alluges auuinitiques dans les circuits

it. d eau pour la production d Energie. Conic *rence presentie au~

1159-

~

,. . ,. .# . f h, .Wh . .*. d. . ' . * - * ggP . ,.

' - a f Msh'pyrity sicket.Trans. ASM, Vol. 53, p. 349 0961). Our comments will include a very brief review of ourtest results on Inconel 600 and then we wish to raisc a,- .

~

DISCUSSIONS question on the SCC behavior of Inconel 600.i in oi.r. laboratories, investiptions are in progress to

J. H. Westbrook, Goswret Electric Corp.: determine the longterm SCC characteristics ofinconct 600

At the' !Watreal grain boundary meeting next I",the boiling water reactor environment. For purposes of*

m nth,U l Dr. Floreen and I will report some results on tius review, only the long term test data will be presented,

highly pure Ni.S binary alloys which I believe are verycomplementary to and confirmatory of the very interesting si w u nstudies you have just described to us. Our alloys raaged L e uss.e sse e v w s cnfrom about 20 ppm S toless than 1 ppm.S (!)and we were a _ _

,,,,%,,,,,,- .- -

monitoring the grain boundary interaction with S by the, g,,

rnicrchardness technique we have previously reported (Acta .,,, . , , , u,,,..,.

Met., Vol.17, p. I175 (1969)). Quenching from 900 C |", ",,,,,,,* y,;,,',,'','"," -**"' gg [| no-8 u,

shows no grain boundary hardening for all compositions;slow cooling from that temperature shows an amount of " """"" Z ' """' |%%| u" 'y*

.hardening decreasing with decreasing S but still sensible at * ==-=*a-- *** *" -

<1 ppm S. Reheating, after quenching, to modest tempera. m,,,,,,,,,,,.,_,,,,,,,,,_

tures (100 to 700 C) brings ell alloys to a steady state grain ..

boundary hardness whose value is a* function of sulfur .In the test program, a uniaxial tensile specimen of>

content.ne kinetics of this grain boundary hardening are inconel 600 failed by intergranular stress corrosion in 550such that it is impossible to maintain a soft grain boundary F water (0.2 ppm Or,0.5 ppm Cl-). This specimen'wasat room tempemture for more than a few minutes following tested at 125% of the 550 F yield strength.ne specimena 900 C quench. Herefore to examine the possible effects was of a crevice configuration,Le., a foil band of Inconelof sulfur. grain boundary interaction on a bulk property,it 6JO was v rapped around the gage length and the failureis necessary to make measurements at sub. normal tempera. occurred after 6633 hours in the crevice region. Duplicatetures. Accordingly, tensile specimens were tested at liquid companion specimens have not failed after 11.477 hours ofN temperature for two conditions: (1) slow cooled from testing. Other creviced specim' ens in triplicate have not'900 C, and (2) quenched from 900 C tc ice wa:er and failed after 11,477 hours of exposure at stress levels of 125, 5

immediately to liquid Ns. All alicys for condition (2) 150, and 200% of the 550 F yield strength in simulatedBWR water (0.2 ppm 0 ).These tests are continuing.shiwed 80 90% RA and predominantly transgranular frac. 2

ture. All alloys for condition (1) shawed much reduced RA Rese test data form the basis for our question on the."

figures in the range 30 40% (the more so the greater the-S ~ SCC behavior of Inconel 600 which is related to the effectcontent), and with accompanying trieresse in the propor. of temperature on the SCC of Inconel 600. M. Gralltion of IG failure. Although these experiments are purely presented test results on specimens exposed at 300 C(572mechanical and not electrochemical, they do show quite F) and 350 C (662 F) while our tests were , performed atdirectly the powerful role of even very tiny amounts of S 288 C (550 F). We would like to ask Mr. Grail to commentand its interaction with the grain boundary. Whether the on the possible existence of a temperature threshold beluw

~ laster phenomenon is properly to be regarded as equilib. which SCC will not occur?rium segregation, vacancy promoted nonequilibrium segre.sation, or conventional precipitation is yet .to be deter. Authors' Reply:mined. Perhaps each plays a role in its proper concentration As a matter of fact, we never performed experimentssange. on Inconel 600 at temperatures below 300 C;most of our-

'

work was performed at 350 C.Authors' Reply: Taking into account the general scatter observed, the

These results are very interesting. Thank you for incubation time, for example, we do not consider that there-. reporting them. They show that sulfur. undoubtedly. plays is.a.significant. difference.between the results.obtained 2t - . _ _

an important role in'the intergran'Gla'ij,Inisefih.nickef : ' these twoiterhperatures (300 ani350C)in high-resistMty[E# #

and presumably in high nickel sJ1oys,'

dcoxygenated water.For lower temperatures,and in different environments,-

the possibility exists for a lower susceptibility to cracking.UINdw published, Canadian Met Quarterly Jan/ Mar (1974). but we have no data to support this.

.

.

1160.

.

..

i

' Joint - 2/27/84>.-

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