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COMPARAISON DE LA RESISTANCE A LA CORROSION SOUS CONTRAINTE EN MILIEU PRIMAIRE DES METAUX FONDUS DE TYPE 152,182 ET 82

COMPARISON OF PWSCC RESISTANCE OF INCONEL 152 WITH WELDING ELECTRODE 182 AND 82

Electricité de France Direction des Etudes et Recherches

SERVICE HÉACTETJRS NUCLÉAIRES ETECHANGETJRS Département Etude des Matériaux

Décembre 1993

BUISINED. VAILLANTE GIMOND C. VIDAL P.

COMPARAISON DE LA RESISTANCE A LA CORROSION SOUS CONTRAINTE EN MILIEU PRIMAIRE DES METAUX FONDUS DE TYPE 152, 182 ET 82

COMPARISON OF PWSCC RESISTANCE OF INCONEL WELDING ELECTRODE 152 WITH WELDING ELECTRODE 182 AND FILLER METAL 82 Pages: 00021 94NB00108

Diffusion : J.-M. Lecœuvre EDF-DER Service IPN. Département SID © Copyright EDF1994 1, avenue du Général-de-Gaulle 92141 Clamart Cedex ISSN 1161-0611 SYNTHÈSE:

Les métaux déposés à l'aide de l'électrode 182 (15 % de chrome) et du £1 TIG 82 (20 % de chrome) ont été trouvés sensibles à la corrosion sous contrainte en milieu primaire. Afin d*?méliorer la résistance à la corrosion, INCO a donc développé un Alliage 152 à plus forte teneur en chrome (30 %). L'ensemble des essais sur éprouvettes selles-de-cheval, en traction lente ou sous charge constante conduits en milieu primaire à 360°C et des essais sur U-bends en vapeur dopée à 400°C, ont démontré 3e meilleur comportement de l'Alliage 152.

D. BUISINE, F. VAILLANT C. GIMOND*, P. VIDAL** * Framatome, ** EDF/SQR

94NB00108 (HT44/COM1678-A)

EXECUTIVE SUMMARY :

Weld metals 182 (15 % ) and 82 (20 % chromium) were found to be sensitive to primary side cracking. In order to improve corrosion resistance, INCO has developed weld metal 152 (30 % chromium). RUBs, CERTs and constant-load tests performed in primary water at 360°C and U-bend tests in doped steam at 400°C have demonstrated mat Alloy 152 exhibited the best behaviour.

94NBM108 (HT44/COM1678-A) COMPARISON OF FWSCC RESISTANCE

OF INCONEL WELDING ELECTRODE 152

WITH WELDING ELECTRODE 182 AND FILLER METAL 82

1 - Background

Alloy 600 used as a steam generator tubing material or in components of the primary circuit (vessel head control rod drive mechanism CRDM penetra­ tions) has been found to be susceptible to stress corrosion cracking in primary "wa­ ter, [1]. Then, Alloy 690 has been introduced because of its better resistance to cor­ rosion [2] ; this is probably due to its higher chromium content (near 30 %).

It was demonstrated that weld metals 182 (15 % chromium) and 82 (20 % chromium), were sensitive to cracking in primary environment, [3]. In order to perform welding of nickel base components of the primary circuit, FRAMATOME has proposed to use weld metals with a 30 %-chromium content : INCO Electrode 152 and Filler Metal 52.

In order to ensure the acurate properties of the proposed alloys, PWSCC resistance of Alloy 152 has been investigated and compared, to SCC-resistance of Alloys 182 and 82, [4].

2 - Main results

SCC-tests were conducted in severe conditions : in primary water with (H2 : 4 bar, injection at 125°C) at 360°C with Reverse U-bends (RUB), Constant Elongation-Rate Tests (CERT) and constant-load tests (0.9 UTS), and in (halide)-doped steam at 400°C on flat U-bends. For experimental conditions, see appendix 1. The various results are collected in appendix 2, and only the main re­ sults are summarized hereunder.

SCC sensitivity of as-welded Alloy 182 was confirmed, with rapid cra­ cking in RUB tests (time to cracking : 500 to 2000 h) and in a constant-load test performed at a nominal stress (F/So) of 450 MPa (time to failure : less than 100 h). Moreover, failure has been observed during CERTs after a 3.4 %-elongation.

7 Kller Metal 82 in the as-welded condition has exhibited a better beha­ viour : only 1 (on 4) KUBs has cracked within 2000 h and CERTs have shown that a 27 %-elongation could be reached before failure with SCC defects.

On the opposite* as-welded Alloy 152 has exhibited a very good beha­ viour, since no stress corrosion cracking was observed in any performed test (RUBs and constant-load tests : no failure in 5000 h). During CERTs, failure has occured after a 25 %-elongation. No SCC-cracks have been observed on these spe­ cimens, despite preexisting "hot-cracks" resulting from the welding operation.

3 - Conclusion

SCC-sensitivity of welded Electrode 182 and Hller Metal 82 was confir­ med in primary environment. AH the corrosion tests have demonstrated the ex­ cellent behaviour' of the candidate Electrode 152 in the as-welded conditions. Experiments have still to be performed on Filler Metal 52.

8 References

[1]- "La corrosion sous contrainte de l'Alliage 600 dans l'eau à haute tempéra ture". EDF report HT40/TJ» 729-A, 21 June 1990.

12]- F. VAILLANT, F. PICARD - "Etude de la corrosion sous contrainte de TA1 liage 690 dans le milieu primaire des REP". EDF report HT45/NEQ1234-B, 16 October 1991.

13] - F. PICARD, P. VIDAL - "Resistance à la corrosion sous contrainte des Alliages 82,182 et 182 à. 19% de chrome, et suite du pxo^arnme". EDF report HT47/NEQ1296-A, 2 September 1991.

[4] - D. BUISNE, F. VAILLANT - "Programme d'étude du Département EMA concernant le soudage de l'Alliage 690". EDF report HT44/PRE 1432-A, 20 January 1993.

9 APPENDIX 1

EXPERIMENTAL CONDITIONS £-MATERIALS

INC01NIX152 : lot 49 A8 (Wt %)

|c S p Sa Mo m Cr Mo Fe Nb Ti Cu Co ljU| 0.040 0.01 O.009 0.44 3.29 54.78 29.72 0.20 9.68 L59 0.04 0.07 0.09 0.04

Alloy 182, specified values, RCC-M code (Wt %)

c S P Si Mn Ni Cr Mo Fe Nb Al Ti Cu Co

«20.1 < si 5- 2:59 13- - S10 l- - si £0.5 <0.1 0.015 0.03 9.5 17 2.5

Alloy 82, specified values, RCC-M code (Wt %)

C S P Si Mil Ni Cr Mo Fe Nb Al Ti Cu Co

£0.1 5 <0.5 2.5- St 67 18- - £3 2-3 - £0.5 <0.1 0.015 0.03 3.5 22 0.75

All materials studied in as-welded coaditions

H 3^jSCfcXESIS

• Doped Steam (30 ppm of Ci", F", SO4—): - 40Û°C, 202 bar, 0.8 bar of %, - performed on bent flat specimens (1 and 12 % strain), -100 hours.

• Primary Water : - 360 °C, 1000 ppm B, 2 ppm Li, 3 bar H2, - performed on : RUB's, CERT,

Constant Load Tests, - up-to-now, 4500 h on RUB's and 4000 h on Constant Load Tests

12 CERT

Constant Elongation Rate Test

Inconel 600 Steam Generators studies have demonstrated that strain rate, rather than stress, is the more accurate parameter to describe PWSCC

So, in CERT, a tensile test is performed in the desired environment (in our case Primary Water). The elongation rate is very low so that, if the material is susceptible to SCC, a crack could occur during the test.

The mechanical properties of the tested specimen are then modified by SCC occurence. A test in an inert environment (Argon) is systematicaly performed, as a reference, to measure the mechanical properties of the material in this kind of tensile test (see attached figure ).

CERT is usualy considered as being a very severe test which allows to get a good comparison of nickel base alloys in terms of SCC.

It is generaly considered that a good behaviour in this test (no Stress Corrosion Cracking) is a warranty for a good behaviour in service conditions.

13 4,r POPED gTEAMKESHLTS

6 specimens for 1 % strain and 3 specimens for 12 % strain,

Alloy 182 : all specimens cracked after 100 hours,

INCONEL 152 : no crack after 100 hours.

14 TIF

-B*SE •i it iB'BE

•JB'SE

t c B'BE c Q. E e c o I • B'SI E

• B'BI

0-g

-Le S S CO in eu —« U

15 APPENDIX 2

RESULTS

16 5>gRiMAin»rwAiicïSliiilll

Tests on RUB's

Binocular examination ÇEM! Bin. examination

Initial 500 h 1000 h 1500 h 2000 h 2500 h 3500 h 4500 h

Alloy - - - - sec - sec sec sec (5 mm) (5 mm) (7 nun)

182 - sec - - - see (5 mm) (Oimirj" depth)%- 3 spec - - - sec - sec (3 mm) <0.«mm depth)

------

Alloy Ml ------

82 - - - - sec - - sec (limn) (9 mm)

4 spec.

IN. small No evolution - No evolution

defects 152 No evolution .- small * -welding 3 spec. (0.2 to 0.6 defects mm) No evolution

No PWSCC observed after 4500 hours on INCONEL 152

17 RUB's

Examination of a Stress Corrosion Crack on one Ailoy 182 RUB

18 $gBRIMjPEy;WA£^^

CERT

1 - Alloys Alloy 182 Alloy 82 INCONEL 152 Environ­ Argon Argon Argon ment PW PW PW PW PW 6 9S1QT7 4AWT8 8.3JL0-* nor6 &310-* 4A10"8 3.7J0-8 S (s-1) nor Time 110 110 138 107 1472 89 1513 1793 (h) E (%) 36.6 0.9 3.4 35.6 27.1 30.6 25.1 23.1 (interr­ upted) U.T.S 534 379 380 517 443 527 521 527 (MPa) Max. 731 385 392 695 555 684 658 689 Stress (MPa)

Crack - 0 1800 0 1000 — 500*; 0 (fracture surface 800 \* s % exam, urn) s s

Obser­ sma& NC No sec NC sec welding No No vation sec defect sec sec * a welding defect of 500 urn depth has been identified on the specimen

No PWSCC on INCONEL 152 : neither initiation, nor propagation (even with the presence of a small welding defect)

19 5-PrâM^YWAT^^

Constant Load Tests

Alloy 182 : PW at 360 °C

Stress = 450 MPa

Rupture after 96 hours

SCC crack = 1700 urn

Tests at 325 °C (400 and 450 MPa) and tests at 360 °C (400 and 350 MPa) are in progress.

INCONEL152: PWat360°C

Stress = 607 MPa (0.9 U.T.S)

No SCC after 4000 hours

20 CERT

Examination of a Stress Corrosion Crack on one Alloy 182 specimen

Cross section of the specimen

Longitudinal section of the specimen

21 CERT

Examination of a Stress Corrosion Crack on one Alloy 82 specimen

Cross section of the specimen

Longitudinal section of the specimen

22 CERT

Examination of a pre-existing small defect on one INCONEL152 specimen

Cross section of the specimen

Longitudinal section of the specimen

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Numéro du document : 94NB00108

Titre COMPARAISON DE LA RESISTANCE A LA CORROSION SOUS CONTRAINTE EN ILIEU PRIMAIRE DES METAUX FONDUS DE TYPE 152, 182 ET 82

Auteurs : BUISINE D./VAILLANT F./GIMOND C/VIDAL P.

Source : COLL. NOTES INTERNES DER. PRODUCTION D'ENERGIE (HYDRAULIQUE, THE Serial :

Référence du document : SANS

Nombre de pages: 0021 Nombre d'exemplaires : 001 Support : P