Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Corrosion Investigations of Steels in Pb-Bi at FZK
J. Konys, G. Müller, J. Knebel
• Materials
- Materials and test parameters for corrosion investigation
• Test equipment
- Stagnant liquid metal test stand COSTA
- Liquid metal loop tests
• Results
- Corrosion in stagnant liquid lead
- Discussion of corrosion in stagnant Pb
- Differences between corrosion effects in Pb and Pb-Bi
- Corrosion in flowing lead
- Comparison results obtained under stagnant and flowing conditions
•Conclusions
Content
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Materials and test parameters for corrosion investigation in lead
Stagnant Lead Tests:Materials: 1.4970, OPTIFER IVc, MCrAlY coatings,
surface alloyed 1.4970 and OPTIFER IVc,Dimension: small specimens 2 x 10 x 20 mm,Temperature: 550 °C,Oxygen concentr.: 8•10-6 at%
Loop Tests at IPPE:Materials: 1.4970, 1.4948, OPTIFER IVc, EM10Dimension: rods 8mm x 110 mmTemperature: 400 °C and 550 °C Oxygen concentr.: 5•10-4 at%Flow velocity: 2 m/s
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Structure of 1.4970 after surface alloying with Al (GESA treatment )
30 40 50 60 70 80
0
50
100
150-Fe
-Fe
-Fe
max. 400 cps
2
original
cps
0
50
100
150
-Fe-Fe -Fe
-Fe -Fe
GESA
0
50
100
150-Fe+FeAl
-Fe+FeAl-Fe-Fe
FeAlFeAl
GESA+Al
10µm
bulk
alloyed layer
Cross section of alloyed layer
Structure analysis
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Stagnant liquid metal test stand COSTA
furnace
tube
thermostatoxygendetector
steel-specimenPb
flowcontrol
Ar5%H2
moisturesensor
moisturesensor
Ar
water
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Conceptual Scheme of CM-2 Lead Loop (IPPE, Obninsk)
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Results of tests in stagnant Pb!
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Protective layer formation on steel in leadwith controlled oxygen concentration
Cross section of the typical structure of a test specimen after 3000 h in liquid Pb at 550 °C.Lead in the upper part contains SiC grains from grinding.
100 µm
100µm
bulk material
corrosion layer
Pb
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Original and GESA Al-alloyed 1.4970 after 3000 hin stagnant lead at 550°C and an oxygen content of 810-6 at%
-15 -10 -5 0 5 10 150
20
40
60
80
100
Con
cent
ratio
n [a
t %
]
Depth [µm]
Original +spinel in grain boundary
Fe(Fe1-x
,Crx)
2O
4
+ Ni
Fe3O
4Pb
Fe Cr Ni Pb O
0 2 4 6 8 10 12 14 16
0
10
20
30
40
50
60
70
Con
cent
ratio
n[at
%],
O-N
et I
nt.
Depth [µm]
Fe Cr Ni Pb O Al
Original Al-alloyed by GESA
Concentration profiles
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Original and GESA Al-alloyed OPTIFER IVc after 3000 hin stagnant lead at 550°C and an oxygen content of 810-6 at%
Original Al-alloyed by GESA
Concentration profiles
-20 -15 -10 -5 0 5 10 15 20 25 300
20
40
60
80
100
Pb
Originalcompostion
Diffusionzone withprecipitationof
Fe(Fe1-x
,Crx)
2O
4
Fe(Fe1-x
,Crx)2O
4
Fe3O
4
Fe Cr Pb O
Con
cent
ratio
n [a
t %
]
Depth [µm]
-2 0 2 4 6 8 10 12 140
20
40
60
80
100
Pb
Fe Cr Pb Al O
Con
cent
ratio
n[at
%],
O-N
et I
nt.
Depth [µm]
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Corrosion Investigation of GESA treated MCrAlY Coating in stagnant Pbafter 3000 h at 550°C and an oxygen content of 810-6 at%
100 µm
MCrAlY
Pb
No measurable corrosion attack after 3000 h!
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
OPTIFER IVc after 470 h at 550 °C in the gas atmospherewith H2/H2O = 0.4 (= 10-25 bar)
element concentration
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Structure analysis of OPTIFER IVc after 500 hat 550 °C in the gas atmosphere (H2/H2O = 0.4)
OPTIFER IVc OPTIFER IVc Al alloyed by GESA
30 35 40 45 50 55 60 65 70 75 80 850
50
-Fe(Al) + FeAl
FeAl
-Fe(Al) + FeAl
0 h
110 h
210 h
500 h
cps
2
0
50
0
50
0
50
FeAl
30 35 40 45 50 55 60 65 70 75 80 85
050
100150 -Fe
-Fe -Fe0 hmax. 500 cps
2
cps
050
100150
20 h
110 h
050
100150
210 h
050
100150
HH
M
M HH
H
M
500 h
050
100150
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Structure analysis of 1.4970 after 500 hat 550 °C in the gas atmosphere (H2/H2O = 0.4)
30 40 50 60 70 80
050
100150200
-Fe-Fe
-Fe-Fe max. 400 cps
0 h
2
cp
s
050
100150200
110 h
050
100150200
210 h
050
100150200
M-Fe-Fe -FeHMM -Fe
500 h
30 40 50 60 70 80
0
50
100
150
FeAlFeAlFeAl -Fe-Fe 0 h
2cp
s
0
50
100
150
110 h
0
50
100
150
210 h
0
50
100
150
-Fe-Fe
-Fe FeAlFeAl FeAl
FeAl
500 h
1.4970 1.4970 Al alloyed by GESA
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Discussion of corrosion in stagnant lead
O 2- Fe O3 4
pore belt
bulk material
oxygenin solution
spinelprecipitations
original surface
Fe (Fe Cr ) O2 + 3+ 3+2 4
(Fe Cr ) O ?1-x x 2 3
FeFe
2+
3+ 1-x x
Oxide layer formation schemeGrowth of spinel and diffusion zoneas a function of time at 550 °C
spinel
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Comparison of Pb and Pb-Bi corrosion at 550 °C, 8•10-6 at% Oxygen
OPTIFER IVc after 800 h in stagnant Pb-Bi OPTIFER IVc after 800 h in stagnant Pb-Bi OPTIFER IVc after 800 h in stagnant Pb
Solubilities in Pb and Bi
Bi (at 600°C)[at%]
Pb (at 600°C)[at%]
Ni 21 2Cr 0,056 0,02Fe 0,017 0,001
The higher solubility in Bi may causehigher dissolution attack of Pb-Bi.
Increase of oxygen activity!
Pb-Bi Pb
bulkbulk
corrosion layer oxide layer
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Results of tests in flowing Pb!
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Exposure to flowing Pb
EM 10 3000 h at 550 °C
OPTIFER IVc2000 h at 550 °C
50 µm 50 µm
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EM 10 for 3000 h in flowing Pb at 550 °C
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Exposure to flowing Pb
Optifer IVc 3000 h at 400 °C
Optifer IVc2000 h at 400 °C
50 µm 50 µm
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Exposure to flowing Pb
1.4948 3000 h at 550 °C
1.49482000 h at 550 °C
50 µm50 µm
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Exposure to flowing Pb
1.4970 3000 h at 550 °C
1.49702000 h at 550 °C
50 µm 50 µm
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Exposure of specimens in flowing Pb (IPPE loop) at 550 °C
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Comparison of oxide scale growth in stagnant Pb (8•10-6 at% Oxygen)and flowing Pb (5•10-4 at% Oxygen) at 550 °C
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
Conclusions
• Oxide layers can effectively prevent the steel from leaching of the alloy components.
• To maintain the oxide layers over long exposure time it is necessary to controlthe oxygen concentration in lead.
• By this procedure corrosion is changed from that of solution attack to that of oxidation.
• Thus, it is needed to find materials that form stable protective oxide scalesunder oxygen control in liquid lead.
• No corrosion attack at all is observed if Al is alloyed into the surface.
• Oxide scale formation in liquid lead obeys the same principle mechanismsas in controlled gas atmosphere.
• There are no principal differences between results of tests in stagnant and flowing lead.
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