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Update on SCC Crack Growth Testing on Dissimilar Metal Welds and Overlays at PNNL
	ML18346A069
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Issue date:	11/28/2018
From:	Margaret Audrain, Bruemmer S, Olszta M, Toloczko M; Office of Nuclear Regulatory Research, Pacific Northwest National Laboratory
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	Margaret Audrain
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Update on SCC Crack Growth Testing on Dissimilar Metal Welds and Overlays at PNNL Steve Bruemmer, Matt Olszta and Mychailo Toloczko Pacific Northwest National Laboratory Research Supported by U.S. Nuclear Regulatory Commission NRC Project Manager Meg Audrain Alloy 690/52/152 PWSCC Research Collaboration Meeting November 28, 2018 Tampa, FL Disclaimer: The work reported in this paper was supported by the Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission. The views expressed in this paper are not necessary those of the U.S. Nuclear Regulatory Commission.

SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 182/52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M Completed SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

Presentation Topics

PNNL Tests on Alloy 152/152M and Alloy 52/52M/52MSS Weld Metals Alloy 152/152M Welds: 8 tests on 3 welds CT013, CT017, CT018, CT052 & CT135 - MHI Alloy 152 U-groove (plus affect of PWHT and L-S versus T-S orientation)

CT049 & CT080 - ANL Alloy 152v2 DM Weld CT081 - KAPL Alloy 152M V-groove DM Weld Alloy 52/52M/52MSS Welds: 11 tests on 8 welds CT024 & CT032 - AREVA Alloy 52 Butt Weld CT025 & CT033 - MHI Alloy 52 U-groove Weld CT120 - ENSA DPM Alloy 52 Weld CT040, CT042 & CT043 - KAPL Alloy 52M Narrow Groove Welds (plus affect of refuse passes)

CT137 - ENSA Alloy 52M Weld CT134 - EPRI Alloy 52M Repair Weld CT050 - Special Metals Alloy 52MSS Weld 15%CF Alloy 152/152M/52/52M Welds: 4 tests CT138 & CT139 - ENSA Alloy 52M & MHI Alloy 52 CT140 & CT141 - MHI Alloy 152 & EPRI Alloy 152M

PNNL Tests on Alloy 152/152M and Alloy 52/52M/52MSS Weld Metals PNNL constant K crack growth measurements on weld metals range from no growth to ~5x10-9 mm/s with most <2x10-9 mm/s.

Surprisingly no correlation between SCC CGRs and %IG, highest IG observed for two alloy 152 welds with low CGRs.

PNNL Tests on Alloy 152/152M and Alloy 52/52M/52MSS Weld Metals PNNL measurements on 11 welds agree well with GEG data on 11 welds including 3 common welds tested at both labs.

Higher SCC CGRs discovered by ANL on two welds (same weld wire) with one weld tested at PNNL and GEG.

Good agreement (low CGRs) among the 3 labs for 4 other welds.

PNNL Tests on 15%CF Alloy 152/152M and Alloy 52/52M Weld Metals SCC crack growth tests were performed on four high-Cr welds in the as welded + 15% cold forged (CF) condition to support the NRC/EPRI SCC initiation project. This condition should be more severe that a worse-case repair weld.

20 22 24 26 28 30 32 34 1.40 1.80 2.20 2.60 3.00 3.40 3.80 4.20 0

1000 2000 3000 4000 5000 6000 7000 8000 outlet conductivity (µS/cm) crack length from notch (mm) time (hrs)

CT138&39: 0.5T CT - ENSA DPM A52M Butter 15% CF PNNL #1 & MHI A52 U-Groove 15% CF PNNL #1, 360-290ºC, 1000 ppm B, 2.0 ppm Li, 25-5 cc/kg H2 Test Overview ENSA A52M Butter 15%CF PNNL #1 MHI A52 U-Groove 15%CF PNNL #1 Constant K (1) 5.6e-09 mm/s

~7e-10 mm/s Constant K (2)

~7e-10 mm/s 5.2e-09 mm/s Constant K (3) 3.1e-09 mm/s

~6e-10 mm/s 290C 320C 360C 1.1e-09 mm/s

<5e-10 mm/s Constant K (4) 325C 360C Constant K (5)

Constant K (6) 3.6e-09 mm/s 5.1e-09 mm/s 1.0e-09 mm/s 1.7e-09 mm/s Restart Constant K (7)

Constant K (8) 5.4e-09 mm/s 7.6e-09 mm/s

~9e-10 mm/s 1.6e-09 mm/s 30 MPam 35 MPam

PNNL Tests on Alloy 152/152M and Alloy 52/52M/52MSS Weld Metals Cold work increased the yield strength by ~20% and SCC growth rates over the as-welded materials, however maximum rates remained below 1x10-8 mm/s for all 4 15%CF materials.

Measured SCC rates suggest a continuous increase in susceptibility with hardness for cold-worked alloy 690 materials. Low SCC growth rates (<~10-8 mm/s) at hardness values at <~240 HV.

Alloy 52M repair weld exhibits SCC rates of ~1x10-9 mm/s even though hardness level has reached ~260 HV.

Results on 15%CF alloy 52/52M/152/152M welds reveal low SCC growth rates

(<~8x10-9 mm/s) at hardness values reaching ~300 HV.

Correlation Between Hardness and SCC Growth Rates 8

~30 MPam Estimated Hardness Range for As-Welded Alloy 152/52 15%CF MHI 52 15%CF IHI 152M 15%CF ENSA 52M 15%CF MHI 152 EPRI 52M Repair SCC tests on 15%CF specimens reported at 2016 Meeting.

Presentation Topics SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 182/52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M Completed SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

PNNL CS/LAS-Alloy 152/52M Dilution Zone and Fusion Line Testing LAS LAS Alloy 152 Fe enrichment and Cr/Ni depletion CT specimens machined to evaluate Fe-rich, Cr-depleted alloy 152 adjacent to LAS interface where aligned grain boundaries are identified.

PNNL CS/LAS-Alloy 152/52M Dilution Zone and Fusion Line Testing Alloy 152/52 Dilution Zone (DZ) and Fusion Line (FL) Tests CT065 & CT083 - KAPL Alloy 52M-CS DZ/FL test (plus PWHT)

CT066 & CT082 - KAPL Alloy 152M-CS DZ/FL test (plus PWHT)

CT117 - ANL Alloy 152v2-LAS DZ/FL test #1 CT119 - ANL Alloy 152v2-LAS DZ/FL test #2 CT136 - EPRI 52M-LAS Temper Bead DZ/FL test CT142 & CT143 - NNL Dual Wire 52i-LAS buildup 24Cr Fusion Line and LAS/CS HAZ Cracking FL & LAS/CS HAZ can be SCC susceptible if PWHT not applied.

Dilution Zone Cracking Most tests have revealed transgranular cracking and low SCC growth rates in DZ regions.

Altered microstructures and favorably aligned boundaries have been identified in a few DZ regions with local Cr levels dropping to 20-24% at these boundaries.

Higher CGRs (~1x10-8 mm/s) have been observed in tests with IG cracking along these favorably aligned, Cr-depleted boundaries.

Presentation Topics SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 182/52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M Completed SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

PNNL SS - Alloy 152/52M Fusion Line Testing Stainless Steel - Alloy 152/52M Fusion Line (FL) Tests CT075 & CT076: MHI Alloy 152 - 304SS U-groove DM Weld CT146: ANL Alloy 152 - 308SS DM Weld CT147: EPRI WRTC Alloy 52M - 316LSS DM Weld Microstructure and Microchemistry No distinct microstructural change, nor significant dilution zone observed in the alloy 152/52M adjacent to the SS interface.

SCC Response All specimens with crack path aligned along FL or within adjacent alloy 152/52M weld have exhibited low SCC growth rates and transgranular cracking.

SCC resistance appears to results for the fact that neither aligned grain boundaries nor a dilution zone is created during DM welding.

Higher corrosion fatigue CGRs observed when the crack path deviated into the SS versus the Ni-base alloy weld metal.

Alloy 152/52M - SS Interface Specimens:

CT146 and CT152 Side Grooves Examinations of CT146 and CT152 side grooves illustrating the intended crack path for SCC crack growth testing.

SEM analyses revealed no significant microstructural or microchemical changes in the welds adjacent to the SS interface.

14 Alloy 152 LAS 308SS Alloy 52M 316LSS CT146 CT152

PNNL Tests on SS - Alloy 52M Interface Regions on Dissimilar Metal Welds Crack growth tests have been performed evaluating SS/152 weld interface regions with no indication of SCC susceptibility.

4 6

8 10 12 14 16 18 20 22 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 0

1000 2000 3000 4000 5000 6000 7000 8000 outlet conductivity (µS/cm) crack length from notch (mm) time (hrs)

CT146&47 - 0.5T CT ANL JC-152 308-152 FL/DZ & EPRI WRTC 316L-52M FL/DZ 30-36 MPam, 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 Test Overview constant K (1) 4.4e-09 mm/s 4.9e-09 mm/s ANL JC-152 308-152 DZ/FL EPRI WRTC DMW 316L/52M DZ/FL constant K (2) 3.3e-09 mm/s 3.0e-09 mm/s constant K (3) 2.8e-09 mm/s 2.8e-09 mm/s 36 MPam 30 MPam 30 MPam

~41 MPam constant K (4) 2.2e-09 mm/s 1.7e-09 mm/s 1.8e-09 mm/s constant K (5) constant K (6) 1.6e-09 mm/s Side Groove Exams

ANL Alloy 152/308SS/LAS Interface Specimen CT146: Side Groove Cracking Examinations of CT146 side groove B revealed that the crack front intersected the 308SS interface region at

~0.7 mm from the notch and propagated near the interface region for ~1.5 mm. However, cracking on side groove A was within the 308SS.

16 Side Groove B CT146 Alloy 152 308SS e-beam weld

SEM and EBSD characterization on DM welds have shown no significant microstructural or microchemical changes at the alloy 152/52M - SS interface regions.

Alloy 152/52M grain boundaries remain perpendicular to the fusion line and not aligned to the SCC growth plane.

Composition dilution in the alloy 152/52M weld metal is minor and Cr concentration remains at ~30% up to ~50 µm of the SS.

Crack growth tests on all four specimens and at all microstructural locations have exhibited transgranular cracking and low SCC growth rates (<5x10-9 mm/s) over a range of K values.

Results to date suggest that alloy 152/52M - SS interface regions have excellent resistance to SCC in simulated PWR primary water.

Summary of Alloy 152/52M - SS Fusion Line Evaluations 17

Presentation Topics SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

PNNL Tests on Alloy 52M/182 Overlay Weld Mockups Ringhals Alloy 52M Overlay on Alloy 182 CT028/CT029/CT034/CT035: Low-to-moderate SCC growth rates for alloy 182 in oxygenated water, low SCC growth rates for alloy 182 in primary water, very low SCC rates at alloy 182/52M interface and in alloy 52M (<2x10-9 mm/s) even at high K.

KAPL Alloy 52M Overlay on Alloy 182 CT150 (completed): SCC response evaluated for alloy 182 weld metal and into Cr-depleted alloy 52M 1st pass.

CT158 (ongoing): SCC response evaluated for alloy 182 weld metal reaching alloy 52M interface and into alloy 52M 1st pass.

EWI Alloy 52M Overlay on Alloy 182 CT156 (ongoing): SCC response evaluated for alloy 182 weld metal and into the alloy 52M 1st pass (limited dilution).

CT161 (ongoing): SCC response evaluated for alloy 182 weld metal reaching alloy 52M interface.

KAPL Overlay Weld Specimen CT150 Side Groove Side grooves revealed that alloy 182/52M interface was

~2.8 mm from notch with 52M 2nd pass at ~3.7 mm.

20 Alloy 52M DZ Alloy 182

Composition Variation from Alloy 182 into Alloy 52M for the KAPL Overlay Weld Cross-section reveals the alloy 182/52M interface at

~3.2 mm and a total crack length of ~3.7 mm, past the alloy 182/52M interface and into a zone of Cr depletion.

21 1.24 mm 3.7 mm 3.21 mm 3.21 mm 4.13 mm 1.85 mm

~24% Cr Alloy 52M

~16% Cr Alloy 182 30%

Cr

Crack Surface Surface Morphology Compared to the Measured Composition Variations Cracking found to propagate across the alloy 182/52M interface and end in the Cr-depleted alloy 52M.

22

Assessment of KAPL Overlay Weld Crack Growth Surface for SCC Corrections Multiple sites of crack propagation beyond 182/52M interface 23

Corrected Crack-Growth Response for the KAPL Overlay Weld Corrected results indicate that fingered growth reached the alloy 182/52M interface early in test and led to decreasing SCC rates after the front entered the alloy 52M dilution region.

24 20 25 30 35 40 45 50 13.0 13.2 13.4 13.6 13.8 14.0 14.2 150 250 350 450 550 650 750 850 outlet conductivity (µS/cm) crack length (mm) time (hrs)

CT150 - 0.5T CT KAPL Alloy 182/52M Overlay Mockup, Alloy 182->52M 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 980s/20s + 2.5 hr, R = 0.5 KAPL A182/52M Overlay Mockup Alloy 182->52M constant K 34 MPam, 2.0e-07 mm/s constant K 980s/20s + 2.5 hr, R = 0.5 constant K 35 MPam, 5.2e-09 mm/s 34.5 MPam, 7.5e-08 mm/s 980s/20s + 2.5 hr, R = 0.5 cycle+hold CGR:

1.2e-06 mm/s cycle+hold CGR:

9.8e-07 mm/s cycle+hold CGR:

1.8e-06 mm/s Alloy 182 Alloy 52M Dilution Region Alloy 52M

Preliminary Interpretation of the First Test on the KAPL Overlay Specimen (CT150)

High SCC growth rates (~1x10-6 mm/s) in alloy 182 SCC growth rates decreased to ~2x10-7 mm/s when leading IGSCC fingers reached the alloy 182/52M interface.

SCC growth rate decreased to ~8x10-8 mm/s as the leading IGSCC fingers propagated into the Cr-depleted

(~24% Cr) alloy 52M 1st pass and the main IGSCC front approached the alloy 182/52M interface.

When the entire active IGSCC front entered the Cr-depleted (~24% Cr) alloy 52M 1st pass, the measured SCC growth rate had dropped to ~5x10-9 mm/s.

Additional CT specimens of the KAPL overlay are being tested at PNNL and at ANL to evaluate behavior.

Ongoing Crack-Growth Response for the 2nd KAPL Overlay Specimen CT158 As for CT150, measured SCC growth rate is decreasing as the crack front reaches the alloy 52M interface and enters the dilution zone.

26 20 22 24 26 28 30 32 34 36 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 0

200 400 600 800 1000 1200 1400 1600 1800 2000 outlet conductivity (µS/cm) crack length from notch (mm) time (hrs)

CT158 - 0.5T CT KAPL Alloy 182-52M Pipe Overlay, Alloy 182->52M Test #2 30 MPam, 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 KAPL Overlay Weld Alloy 182->52M Test #2 CT158 Test Overview constant K (1) 3.7e-07 mm/s 52M Interface constant K (2) 2.8->0.7e-07 mm/s 1.4e-07 mm/s constant K (3) 1.9->0.5e-08 mm/s 1.1e-08 mm/s Dilution Zone

Ongoing Crack-Growth Response for the 2nd KAPL Overlay Specimen CT158 Response suggests that fingered growth has reached the alloy 52M interface and IGSCC propagation is occurring within the alloy 52M dilution region.

27 20 22 24 26 28 30 32 34 13.080 13.090 13.100 13.110 13.120 13.130 13.140 800 1000 1200 1400 1600 1800 outlet conductivity (µS/cm) crack length (mm) time (hrs)

CT158 - 0.5T CT KAPL Alloy 182-52M Pipe Overlay, Alloy 182->52M Test #2 Remachined Notch: 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 KAPL Overlay Weld Alloy 182->52M Test #2 30 MPam Previous 2.5h hold = 2.0e-07 mm/s Constant K = 28->6.8e-08 mm/s Constant K 1.9e-08 mm/s 5.3e-09 mm/s 980/20s, R=0.5

+ 2.5h hold 3.7e-08 mm/s 1.1e-08 mm/s

PNNL Tests on Alloy 52M/182 Overlay Weld Mockups Ringhals Alloy 52M Overlay on Alloy 182 CT028/CT029/CT034/CT035: Low-to-moderate SCC growth rates for alloy 182 in oxygenated water, low SCC growth rates for alloy 182 in primary water, very low SCC rates at alloy 182/52M interface and in alloy 52M (<2x10-9 mm/s) even at high K.

KAPL Alloy 52M Overlay on Alloy 182 CT150 (completed): SCC response evaluated for alloy 182 weld metal and into Cr-depleted alloy 52M 1st pass.

CT158 (ongoing): SCC response evaluated for alloy 182 weld metal reaching alloy 52M interface and into alloy 52M 1st pass.

EWI Alloy 52M Overlay on Alloy 182 CT156 (ongoing): SCC response evaluated for alloy 182 weld metal and into the alloy 52M 1st pass (limited dilution).

CT161 (ongoing): SCC response evaluated for alloy 182 weld metal reaching alloy 52M interface.

Ongoing Crack-Growth Response for the 1st EWI Overlay Specimen CT156 Measured SCC growth rates decreased early in the test suggesting that the leading IGSCC fingers reached the alloy 52M interface.

29 20 22 24 26 28 30 32 34 36 38 40 42 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 0

1000 2000 3000 4000 5000 outlet conductivity (µS/cm) crack length from notch (mm) time (hrs)

CT156 - 0.5T CT EWI OL 182->52M #1 30 MPam, 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 Test Overview constant K (1) 16->5.2e-07 mm/s EWI Overlay 182->52M Test #1 CT156 8.7->2.2e-08 mm/s constant K (2) 1.4->0.1e-08 mm/s constant K (3) constant K (4) 7.1e-09->0 mm/s 7.5e-07 mm/s 7.2e-08 mm/s 1.4e-08 mm/s 52M 182 7.1e-09 mm/s constant K (5) 7.5e-09->0 mm/s 6.5e-09 mm/s

Ongoing Crack-Growth Response for the 1st EWI Overlay Specimen CT156 Measured SCC response in the alloy 52M overlay suggesting ligament/contact formation that is removed by cyclic loading.

30 20 22 24 26 28 30 32 34 36 0.296 0.300 0.304 0.308 0.312 0.316 0.320 0.324 0.328 2600 2700 2800 2900 3000 3100 3200 3300 outlet conductivity (µS/cm) a from 850 hours0.00984 days 0.236 hours 0.00141 weeks 3.23425e-4 months (mm) time (hrs)

CT156 - 0.5T CT EWI OL 182->52M #1 30 MPam, 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 EWI Overlay 182->52M #1 constant K 7.1e-09 mm/s no growth 980s/20s, R=0.5

+ 2.5h hold 7.1e-09 mm/s 4.2e-08 mm/s

Ongoing Crack-Growth Response for the 2nd EWI Overlay Specimen CT161 As for CT156, measured SCC growth rate is decreasing as the crack front reached the alloy 52M interface.

31 20 22 24 26 28 30 32 34 36 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 0

200 400 600 800 1000 1200 1400 1600 1800 2000 outlet conductivity (µS/cm) crack length from notch (mm) time (hrs)

CT161 - 0.5T CT EWI Alloy 182-52M Pipe Overlay, Alloy 182->52M Test #2 30 MPam, 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 EWI Overlay Weld Alloy 182->52M Test #2 CT161 Test Overview constant K (1) 8.8-->2.8e-07 mm/s Alloy 182 Alloy 52M 2.7-->1.7e-08 mm/s constant K (2) 3.7e-07 mm/s 1.9e-08 mm/s

Preliminary Assessment of SCC Resistance for KAPL and EWI Alloy 52M Overlay Welds Distinct dilution zone differences are present between the KAPL and EWI overlay welds with strong Cr depletion in the KAPL weld 1st pass and very limited Cr depletion in the EWI weld.

High SCC growth rates (3-10x10-7 mm/s) are produced in the alloy 182 for both overlay welds.

Measured SCC growth rates have decreased by >10X when the crack front reached the alloy 52M interface.

Much lower SCC growth rates are being observed as the crack front moves into the alloy 52M overlay.

Post-test corrections are required to better quantify SCC response for ongoing tests and establish resistance of the alloy 52M overlay.

Presentation Topics SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

KAPL Overlay Alloy 182/52M Interface Specimen CT152: Side Groove Cracking Examinations of CT152 side groove A revealed that the crack front intersected the alloy 182/52M interface at

~2 mm from the notch and propagated along the interface region for ~2 mm. However, cracking on side groove B was transgranular and within the alloy 182.

34 Alloy 52M Alloy 182 Side Groove A

Response for the 1st KAPL Overlay Alloy 182/52M Interface Specimen CT152 Four measurements SCC response and constant K while crack path was partially along the alloy 182/52M interface. Only low SCC CGRs were observed in situ, post test corrections are ongoing.

35 20 22 24 26 28 30 32 34 36 38 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 150 250 350 450 550 650 750 outlet conductivity (µS/cm) a from 150 hours0.00174 days 0.0417 hours 2.480159e-4 weeks 5.7075e-5 months (mm) time (hrs)

CT152 KAPL OL 182/52M Interface Specimen #1 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 KAPL OL 182/52M Interface #1 Constant K 5.2e-09 mm/s 4.1e-09 mm/s 980s/20s, R = 0.5 +

2.5h hold 5.2e-09 mm/s

Ongoing Tests on Alloy 182/52M Interface Specimens from Overlay Welds First test (CT152 - KAPL) with crack growth plane oriented to intersect the alloy 182/52M has just been completed. Crack growth along/near the interface observed on one side groove, but in-situ DCPD measurements reveal low SCC growth rates (2-5x 10-9 mm/s). Post-test characterizations needed and are underway.

Tests on two additional alloy 182/52M interface specimens (CT168 - EWI and CT169 - KAPL) were started this month. Currently moving to intersect interface and assess SCC response at constant K.

Presentation Topics SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens Summary for as-welded, repair welded and cold-worked Crack Growth Testing on Dissimilar Metal Welds Summary for LAS/152 and LAS/52M interface regions Summary for SS/152 and SS/52M interface regions Crack-Growth Testing on Alloy 182/52M Weld Overlays Completed/ongoing SCC tests for alloy 182 into alloy 52M Completed SCC test assessing alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects CT specimens machined to position pre-existing DDC at blunt notch surfaces, constant load testing at high K levels, SEM examinations at exposures times of 3810 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

EPRI WRTC 316L/A52M/152/LAS Weld Blunt Notch Specimen CT148 LAS A52M 316L 152 root 52M IG DDC cracks identified in 52M near the 152 interface High density of aligned IG cracks Position blunt notch specimen to intersect longest cracks E-beam welded 316SS to bottom of sample to be able to fashion 0.5 CT with a blunt notch Region 9 aligned cracks Attempt to position BNCT Blunt notch position

Positioning of Blunt Notch in CT148 39 Initial CT positioning (red) slightly off mark Notch position moved (yellow) to intersect pre-existing DDC cracks (yellow & green)

Attempt to initiate/propagate SCC from aligned IG DDC cracks on blunt notch surface Side A Side B

Pre-Test Examination of CT148 Blunt Notch 40 Side A Side B 1

2 3

4 5

6 1

2 3

4 5

6 Pre-examination showed narrow IG cracks in the middle of the blunt notch region on the order of 50-200 µm long SEM exam down the notch 4

Nb rich segregation highlights dendrite orientations and high-energy grain boundaries IG crack

Crack Growth Response at Constant Load for Blunt Notch Specimens CT148 and CT149 Both specimens reveal a slowing rate of change in crack length consistent with aging effects on DCPD response.

41 20 24 28 32 36 40 44 0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180 0

2000 4000 6000 8000 10000 outlet conductivity (µS/cm) a crack length from 200 hrs (mm) time (hrs)

CT148&149 - 0.5T CT EPRI WRTC 316L-52M DM & EPRI DDC Mockup Welds 360°C, 1000 ppm B, 2.0 ppm Li, 25 cc/kg H2 BLUNT NOTCH Constant Load CT148 EPRI WRTC 316L/52M/152 DM Weld PNNL #1 (~45 MPam)

CT149 EPRI WRTC DDC Mockup Weld PNNL #1 (~41 MPam)

Non Referenced DCPD Stopped for exams at ~3810 h Unloaded to monitor resistivity evolution Reload Stopped for exams at

~8000 h High pseudo K, no cyclic loading

42 Re-Examination of CT148 after 3810 hours0.0441 days 1.058 hours 0.0063 weeks 0.00145 months Re-examination shows very little change in pre-existing weld cracks, few may have grown and/or opened slightly 1

2 3

4 5

6 3

4 6

43 Pre-test 3810 hours0.0441 days 1.058 hours 0.0063 weeks 0.00145 months Several new large (0.2-0.5 mm long, 10-15 µm wide) cracks were observed in the blunt notch near the top side wall along with a few new small cracks.

0.5 mm New long IG cracks New small cracks New small cracks Re-Examination of CT148 after 3810 hours0.0441 days 1.058 hours 0.0063 weeks 0.00145 months

44 Many possible new small (<50 µm long, <5 µm wide) cracks were observed, growth of pre-existing IG cracks.

0.5 mm Re-Examination of CT148 after 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months New small IG cracks New IG cracks

45 Re-Examination of CT148 after 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months Re-examination shows very little change in pre-existing weld cracks, however a few appear to have grown resulting in coalescence.

Re-Examination of CT148 Side Grooves after 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months Re-examination shows no apparent growth of 2 pre-existing long DDC cracks in side groove A.

PNNL Blunt Tests on Alloy 52M Welds with Pre-Existing DDC Cracks CT148 EPRI LAS/152/52M/SS DM Weld Clear indication of new cracks on the blunt notch surface after constant load testing for 3810 hours0.0441 days 1.058 hours 0.0063 weeks 0.00145 months , they do not appear to be related to pre-existing DDC cracks.

Indication of slight crack growth and/or coalescence on the blunt notch surface along with several new small cracks after constant load testing for 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

CT149 EPRI Alloy 52M DDC Mockup Weld No indication of new cracks or growth of existing cracks on the blunt notch surface after 3810 or 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .

Test continuing and currently at an exposure time

>11,000 hours0 days 0 hours 0 weeks 0 months , next examination at ~12,000 hours0 days 0 hours 0 weeks 0 months when decision will be made for next steps.

PNNL Planned Weld Tests in 2019 SCC Crack Growth Testing on Alloy152/152M and Alloy 52/52M/52MSS Weld Metal Specimens ENSA/CIEMAT CRDM weld mockup: alloy 152/52M EPRI 40%+20% DM repair weld mockup: alloy 52M Crack Growth Testing on Dissimilar Metal Welds ENSA/CIEMAT CRDM weld mockup: LAS/152 & 308SS/52M EPRI DM repair weld mockup: LAS/52M & SS/52M Crack-Growth Testing on Alloy 182/52M Weld Overlays Complete ongoing SCC tests for alloy 182 into alloy 52M Complete ongoing SCC tests for alloy 182 - alloy 52M interface Blunt Notch Tests on Alloy 52M Welds with Defects Continue ongoing SCC test, SEM examinations at exposures times of 12,000 hours0 days 0 hours 0 weeks 0 months , decision will be made on next step.

Evaluate possible weld defects in ENSA and EPRI welds.

ML18346A069

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