-NETNUC-%20SCC%20Properties%20and%20Oxidation%20Behaviour%20of%20Candidate%20Materials%20at%20SCW%20conditions

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-NETNUC-SCC Properties and Oxidation Behaviour
of Candidate Materials at SCW conditions
Sami Penttilä

• NETNUC/GEN4FIN meeting
• 03.04.2009, VTT, Espoo

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Content

• Weight gain tests
• SCC susceptibility
• Status of oxidation studies using bellows system
• Summary

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Chemical compositions of the studied alloys (wt-)
Weight gain tests

• Sixteen materials from the four different alloy
  groups for screening stage

Material Chemical analysis
1 P91 0.1Ni 8.3Cr 0.96Mo 0.11C 0.43Mn 0.23V 0.41Si
2 P92 0.02Ni 8.9Cr 0.49Mo 0.08C 0.42Mn 2.1W 0.22V 0.09Si
3 HCM12 0.28Ni 11.9Cr 0.34Mo 0.09C 0.62Mn 1.96W 0.25V 0.34Si 0.45Cu
4 Eurofer 97 8.9Cr 0.11C 0.47Mn 1.1W 0.2V 0.14Ta
5 Eurofer ODS (2) 0.03Ni 9.2Cr 0.02Mo 0.035C 0.4Mn 1.3W 0.21V 0.03Si
6 Eurofer ODS (1) 0.05Ni 9Cr 0.02Mo 0.021C 0.36Mn 1.3W 0.21V 0.12Si
7 PM2000, ODS 0.03Ni 20.1Cr 0.09Mo 0.005C 0.08Mn 0.03V 0.02Si 0.43Ti
8 316NG (LN) 11.3Ni 16.6Cr 2.11Mo 0.014C 0.8Mn 0.42Si 0.07Co 0.23Cu
9 321 9-12Ni 17-19Cr 2Mn 1Si 0.08C gt5C Ti
10 TP347H 10.7Ni 17.6Cr 0.048C 1.8Mn 0.29Si 0.56Nb
11 Sanicro 28 30.6Ni 26.7Cr 3.34Mo 0.015C 0.065N 1.7Mn 0.41Si 0.87Cu
12 BGA4 15.4Ni 22.9Cr 0.14Mo 0.11C 0.19N 6.1Mn 1.5W 0.31V 0.61Nb 0.49Si 2.7Cu
13 15Cr15NiTi (1.4970) 15.3Ni 15Cr 1.18Mo 0.095C 1.68Mn lt0.01W 0.53Si 0.45Ti 0.04Al 0.02Cu
14 Incoloy 800H 30.8Ni 20.5Cr 0.13Mo 0.06C 0.67Mn 0.36Si 0.36Ti 0.26Al
15 Inconel 625 2.6Fe 22.4Cr 9.1Mo 0.02C 0.05Mn 0.12W 3.3Nb 0.07Si 0.25Ti 0.29Al
16 Inconel 690 27-31Cr 7-11Fe 0.05C 0.5Mn 0.5Si 0.5Cu
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Weight gains at different temperatures for
selected alloysafter 600 h exposure to SCW
conditions (25 MPa)
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Weight gain test
Weight gains of 316L pipe with different surface
treatments T 650C, t 1000 h, p 25 MPa and
D02 125 ppb
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316L pipe samples with different surface finishes
after 1000 h exposure to SCW at 650C
machined
as received
grit 600
grit 1200
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Optical images of the 316L pipe samples after
1000 h exposure to SCW at 650C
grit 1200 surface finish
machined surface
oxide thickness 40 50 µm
oxide thickness 2 µm
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Improving corrosion and oxidation behavior of
materials at SCW conditions

1. Chemical composition, Cr content gt 18
2. GB modification ? thermomechanical processing
3. Application of surface treatment, e.g. CW

• Effect of CW
• An enhanced Cr diffusivity
• increased defect density
• Results to a more compact and continuous
  (uniform diffusivity) Cr-oxide layer
• Dense Cr-oxide layer decrease the outward/inward
  transport of Fe and O

Babcock-Hitachi Europe Gmbh, Advanced materials
for AD700 boilers, Milano, Italy, 2005
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SCC susceptibility - SSRT

• T 500C and 650C, p 25 MPa and DO2 125 ppb
• Strain rate of 3x10-7 s-1
• Materials
• 316NG
• 347H
• 1.4970
• BGA4
• PM2000

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Stress-strain curves for the studied alloys under
SCW conditions at 500C and 650C
500C
650C

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SEM images of the fracture surface of alloy
1.4970 after SSRT at 500C
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SEM images of the fracture surface of alloy BGA4
after SSRT at 500C
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Summary of SCC susceptibility after SSRT at 500C
and 650C under SCW conditions
Alloy Maximum stress (MPa) Strain to failure () TGSCC (y/n) IGSCC (y/n) Side craks at the gauge surface (y/n)
347H _at_ 500C 465 45 No No Yes, morphology not identified
347H _at_ 650C NA NA NA NA NA
316NG _at_ 500C Interrupted at 330 Interrupted at 33 NA NA Yes, IG and TG
316NG _at_ 650 C 195 38 Yes Yes No
1.4970 _at_ 500C 675 26 No No Yes, morphology not identified
1.4970 _at_ 650C 360 28 Badly oxidized Badly oxidized Yes, morphology not identified
BGA4 _at_ 500C 425 41 Yes Yes Yes, IG
BGA4 _at_ 650C NA NA NA NA NA
PM2000 _at_ 500C 325 Interrupted at 50 No No No
PM2000 8 _at_ 650C 100 40 No No No
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Oxidation kinetic studies (CER/CEI) using
pneumatic servo-controlled bellows system
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Status of DB-system

• Problems with pressure tube material (316L)
• Problems with welding
• New miniature DB-system has been designed by P.
  Moilanen
• Purpose is to perform mechanical loading (3-PB
  etc.) tests for selected materials at SCW
  conditions
• Oxidation kinetic studies using CER/CEI methods
• CEI and CER analysis have showed that most of the
  commercial materials behave like semiconductors
  under SCW conditions

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Summary

• The oxidation rate of F/M steels is too high for
  SCWR core components even at the temperatures
  below 500C
• Austenitic stainless steels, which have a good
  enough oxidation resistance up to 500 550C
  have been selected as a candidate materials for
  most HPLWR core components
• 20 Cr ODS steel was selected for the fuel rod
  cladding material because of its excellent
  oxidation resistance even up to 650C, its SCC
  resistance and its good creep specifications
• However, the SSRT results in this work are not in
  line with the creep strength specifications
• More studies are needed in the behaviour of high
  Cr F/M ODS steels in supercritical water
• Other problems with the ODS materials are the
  difficulties in welding and high prices
• Therefore these materials are recommended to
  applications where high strength and oxidation
  resistance are needed, but only little additional
  joining is required
• A possible road for the fuel cladding development
  may be coating of austenitic stainless steels or
  F/M steels
• Processes that have been studied are diffusion
  coatings (i.e. slurry application, CVD) and
  overlay coatings (thermal spray, PVD, electroless
  coatings)