Transcript NETNUC SCC Properties and Oxidation Behaviour of Candidate

-NETNUCSCC Properties and Oxidation Behaviour of
Candidate Materials at SCW conditions
Sami Penttilä
NETNUC/GEN4FIN meeting
03.04.2009, VTT, Espoo
VTT TECHNICAL RESEARCH CENTRE OF FINLAND
Content
•
Weight gain tests
•
SCC susceptibility
•
Status of oxidation studies using bellows system
•
Summary
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Weight gain tests
•Sixteen materials from the four different alloy groups for screening stage:
Chemical compositions of the studied alloys (wt-%)
Material
Chemical analysis
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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
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Eurofer ODS (2)
0.03Ni 9.2Cr 0.02Mo 0.035C 0.4Mn 1.3W 0.21V 0.03Si
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Eurofer ODS (1)
0.05Ni 9Cr 0.02Mo 0.021C 0.36Mn 1.3W 0.21V 0.12Si
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PM2000, ODS
0.03Ni 20.1Cr 0.09Mo 0.005C 0.08Mn 0.03V 0.02Si 0.43Ti
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316NG (LN)
11.3Ni 16.6Cr 2.11Mo 0.014C 0.8Mn 0.42Si 0.07Co 0.23Cu
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321
9-12Ni 17-19Cr 2Mn 1Si 0.08C >5*%C Ti
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TP347H
10.7Ni 17.6Cr 0.048C 1.8Mn 0.29Si 0.56Nb
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Sanicro 28
30.6Ni 26.7Cr 3.34Mo 0.015C 0.065N 1.7Mn 0.41Si 0.87Cu
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BGA4
15.4Ni 22.9Cr 0.14Mo 0.11C 0.19N 6.1Mn 1.5W 0.31V 0.61Nb 0.49Si 2.7Cu
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15Cr15NiTi (1.4970)
15.3Ni 15Cr 1.18Mo 0.095C 1.68Mn <0.01W 0.53Si 0.45Ti 0.04Al 0.02Cu
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Incoloy 800H
30.8Ni 20.5Cr 0.13Mo 0.06C 0.67Mn 0.36Si 0.36Ti 0.26Al
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Inconel 625
2.6Fe 22.4Cr 9.1Mo 0.02C 0.05Mn 0.12W 3.3Nb 0.07Si 0.25Ti 0.29Al
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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 alloys
after ~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 = 650°C, t = 1000 h, p = 25 MPa and D02 = 125 ppb
0,007
0,006
2
Weight gain (g/cm )
0,005
0,004
0,003
0,002
0,001
0
machined
as received
#600 grit
#1200 grit
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316L pipe samples with different surface finishes after 1000 h exposure to SCW at 650°C
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 650°C
grit #1200 surface finish
oxide thickness ~ 40 – 50 µm
machined surface
oxide thickness ~ 2 µm
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Improving corrosion and oxidation behavior of materials at SCW conditions
1.
Chemical composition, Cr content > 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 = 500°C and 650°C, 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 500°C and 650°C
500°C
650°C
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SEM images of the fracture surface of alloy 1.4970 after SSRT at
500°C
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SEM images of the fracture surface of alloy BGA4 after SSRT at
500°C
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Summary of SCC susceptibility after SSRT at 500°C and 650°C 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
@ 500°C
465
45
No
No
Yes, morphology not
identified
347H
@ 650°C
NA
NA
NA
NA
NA
316NG
@ 500°C
Interrupted
at 330
Interrupted at 33
NA
NA
Yes, IG and TG
316NG
@ 650 °C
195
38
Yes
Yes
No
1.4970
@ 500°C
675
26
No
No
Yes, morphology not
identified
1.4970
@ 650°C
360
28
Badly oxidized
BGA4
@ 500°C
425
41
Yes
Yes
Yes, IG
BGA4
@ 650°C
NA
NA
NA
NA
NA
PM2000
@ 500°C
325
Interrupted at 50
No
No
No
PM2000 #8
@ 650°C
100
40
No
No
No
Badly
oxidized
Yes, morphology not
identified
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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 500°C
• Austenitic stainless steels, which have a good enough oxidation resistance up to 500 – 550°C 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 650°C, 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)
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