© Fraunhofer IKTS - HySafe...Interconnect alloys – compositions and effects of components Cr Ni C...
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High temperature steels, Interconnection Jochen Schilm , Viktar Sauchuk, Stefan Megel 1st Joint European Summer School on Fuel Cell and Hydrogen Technology 22th August – 2th September 2011 Viterbo, Italy © Fraunhofer IKTS www.ikts.fraunhofer.de Contents Interconnects for SOFC High temperature steels and alloys for interconnects Evaporation of Chromium and Poisoning of electrodes Formation of oxide scales on interconnects Formation of oxide scales on interconnects Protective coatings on interconnects High Chromium und temperature alloys © Fraunhofer IKTS
Transcript of © Fraunhofer IKTS - HySafe...Interconnect alloys – compositions and effects of components Cr Ni C...
High temperature steels, Interconnection
Jochen Schilm, Viktar Sauchuk, Stefan Megel
1st Joint European Summer School on Fuel Cell and Hydrogen Technology
22thAugust –2thSeptember 2011 gp
Viterbo, Italy
© Fraunhofer IKTS
www.ikts.fraunhofer.de
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
Temperaturerangesin SOFC modules
SOFC stacksCombinationmetal-ceramics
850°C
AfterburnerSiSiCCeramicfoam
1300 °C
850 °C
PreheaterSiC glow plug
1200°C
CPOxreformerCorderitecatalyticmonolith
950 °C
© Fraunhofer IKTS
1200 C
Application of High temperature-steels in the SOFC systems
Interconnect in theSOFC stack
Balanceofplant(BOP)intheSOFCmodule Balance ofplant (BOP) in theSOFC module
General requirements:
good thermo-mechanical stability
to guarantee a long life of the system
abilitytoformadenseoxidelayer ability to form a dense oxide layer
to prevent an accelerated oxidation of the material and evaporation of the steel components
chemicalstability chemical stability
to avoid phase and structural changes during the stack operation and thermocycling
excellentimpermeability excellent impermeability
to prevent the leakage of gases
© Fraunhofer IKTS
Stackassemblyofa 1kW CFY-basedSOFC stack
Top plateBiggestCFY Interconnect
130x150 mm
Bipolar plate
Protection-andcontactlayer
Cll Cell
Air
Nickel meshes
Glili
Activearea: 127 cm²
Glass-ceramicsealing
Bottomplatewithcurrentplug
MicaSealingFuel
© Fraunhofer IKTS
Sealing
Requirements to SOFC interconnect
high electronic and thermal conductivity
to reduce resistive losses
Pidittlitfthll Providing temperature alignment of the cell
ability to form a dense conducting oxide layer
to protect the interconnector from further oxidation and from evaporation fthtlttditil of the steel components, to reduce resistive losses
good mechanical stability and thermo-mechanical compatibility with other stack components
titithtkbtdbilitdiththli to maintain the stack robustnessand operability during the thermocyclingand mechanical loading
chemical stability/compatibility under both oxidising and reducing conditions conditions
to avoid the phase and structure changes during the stack operation and thermocycling
excellentimpermeability excellent impermeability
to prevent a mutual penetration of the gaseous species from separated media
© Fraunhofer IKTS
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
Schematic classification and selected properties of steels andalloysforSOFCapplication and alloys for SOFC application
Fe, CrandNiasbasematerials
FeAlloyTEC30…800 °C[10-6K-1]
Chromium-10,0-11,0CTE increases
Austeniticalloys
es do
wn
Stre
ng
thg
based
Ferritic11,0-12,5
Austenitic18,0-20,0
Price go
e
go
esu
p
Iron-Nickel15,0-20,0
Nickel-based14,0-19,0
CrNi
source: S.Megel, Dissertation, Kathodische Kontaktierung in planaren Hochtemperatur-BrennstoffzellenStuttgart:IRBFhGVerlag2009p168
© Fraunhofer IKTS
HochtemperaturBrennstoffzellen, Stuttgart.: IRB FhG Verlag, 2009, p. 168.
Interconnect alloys –compositions and effects of components
CrNiCMnSiAlMinor
1.474217-190.030.121.00.7-1.40.7-1.4S
ZMG232220.330.020.50.40.19Zr, N
Crofer22APU22-240.16<0.03<0.8<0.5<0.5Ti, La
1.484524-2619-22<0.08<2<1-Mo,P
ITM26--<0.1<0.05<0.05Ti, Y2O3
Microstructure
TEC
Oxidescalecomposition
Oxide scale compositionPrecipitation
Adhesion
Inneroxidescale OxidescalecompositionInneroxidescale
Major components determine properties of the alloys
Minor components affect the formation of oxisescales on the surface Long term stability & Chromium evaporation
© Fraunhofer IKTS
Comparison of the thermal expansion of materials forSOFCcomponents SOFC components
238YSZITM
19
21
m/K
ZMG232Crofer221.47421.4845
Cr 24, Ni 19
15
17
CTE
/ppm,
11
13
C
902004006008001000
Temperature/ °C p
CeramicYSZ-materialsforelectrolytedeterminerequirementsofSOFC-steels
© Fraunhofer IKTS
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
Evaporation of the Cr-species from the steel in air
) ( ) ( 5. 1 ) ( 23 2 2s O Cr g O s Cr
) ( 2 ) ( 5. 1 ) (3 2 3 2g CrO g O s O Cr
in humid air:
) ( ) ( 2 ) ( 2 ) ( 5. 1 ) (2 2 2 2 3 2g OH CrO g O H g O s O Cr
) )( ( 2 ) ( ) ( ) (g OH CrO g O H g O s O Cr) )( ( 2 ) ( ) ( ) (2 2 2 3 2g OH CrO g O H g O s O Cr
PoisoningofcathodesduetoreactionswithChromiumoxidesandhydroxides Poisoning of cathodes due to reactions with Chromium oxides and hydroxides
Clogging of pores in electrodes due to deposition of Chromium oxides and hydroxides
M.Stanislowski, Schriften FZJ, Energietechnik. V54 (2006), S18.
Degradation of steel by continuous evaporation of Chromium
© Fraunhofer IKTS
g
Hier noch 1 bis 2 Folien zum Thema Cr-Abdampfungaus denDissertationenrausarbeiten: den Dissertationen rausarbeiten:-Stanilowski: Seite 19 Dampfdrücke von Cr-O-OH-Spezies p
© Fraunhofer IKTS
Degradation of Stacks performance by passivationof the thddtChitifitt cathode due to Chromium-evaporation from interconnect
Deposition ofChromiumoxideinsidetheporousCathodemicrostructure
S. Megel, KathodischeKontaktierungin planarenHochtemperaturbrennstoffzellen, Ph.D. Thesis, ISBN978-3-8396-0066-5Band6SchriftenreiheKompetenzeninKeramikFraunhoferVerlagStuttgartGermany2009
PoisoningofthetriplepointsforthereductionofO2
© Fraunhofer IKTS
ISBN9783839600665,Band6SchriftenreiheKompetenzeninKeramik,FraunhoferVerlag,Stuttgart,Germany,2009
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
Exampleofthe„time-resolved“ oxidationin thesteelat800 °C
1101001000
Logarithmictime scale/ h
Formation ofmultiple oxidelayerwithdifferent properties
source:SDunningJMOhandJCRawersinAlternativeAlloysforEnvironmentalResistanceTMS
Spallingofoxidefromthesurface
DepletionofsteelbyChromiumandManagnese
© Fraunhofer IKTS
source: S. Dunning, J.M. Oh, and J.C. Rawers, in Alternative Alloys for Environmental Resistance, TMS.
Huczkowski: Seite 18 Abhängigkeit der Massenzunahme von Additiven in Cr-Fe-Legierungen
© Fraunhofer IKTS
Oxidation behaviour of HT steels
2020 OuterOxideScale
Formation of outer and inner oxidations
OuterOxideScale
0
20
0
20 OuterOxideScaleOuterOxide Scale
-40
-20
-40
-20
Inner Oxide Scale ness in m
idl
-80
-60
-80
-60 ZMG232 ThicknInnerOxide Scale
01600320048006400-100
-80
-100
-80
Tiih
20 m
Time inh
© Fraunhofer IKTS
Oxidation behaviour of HT steels
016003200480064002020 OuterOxideScale
Formation of outer and inner oxidations
idl01600320048006400
0
20
0
20 OuterOxideScaleOuterOxide Scale
-40
-20
-40
-20
Inner Oxide Scale ness in m
InnerOxide Scale
80
-60
80
-60 ZMG232 Thickn
CroFer22APUBaseMaterial
01600320048006400-100
-80
-100
-80
Tiih
CroFer22APU20 m Base Material
Time inh
© Fraunhofer IKTS
Oxidation behaviourofHT steels
01600320048006400 016003200480064002020 OuterOxideScale
Formation of outer and inner oxidations
01600320048006400 01600320048006400
0
20
0
20 OuterOxideScale
InnerOxideScale
OuterOxide Scale
-40
-20
-40
-20
Inner Oxide Scale ness in m
InnerOxide Scale
80
-60
80
-60 ZMG232 Thickn
CroFer22APU
Base Material
01600320048006400-100
-80
-100
-80
Tiih
CroFer22APU ITM14
20 m
Time inh
© Fraunhofer IKTS
Oxidation behaviourofHT steelsSteel XSFC-1C44Mo20 (Sandvik)
after 800 h oxidationafter 12000 h oxidation
© Fraunhofer IKTS
Oxidation behaviourofHT steels
Breakawayoxidation(ZMG232L @ 850°C)
6400h12000h 3200h
12000h20000h
nCrforZMG232L; Crofer22APU < 15 wt. %
© Fraunhofer IKTS
Cr;
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
Oxidation behaviourofHT steelsCoatedvs. uncoated
Increaseofouteroxidescaleafter oxidationin airat850 oC
40Crofer22APUuncoated
30
Crofer22APU uncoatedITMLC uncoatedZMG232L uncoatedCrofer22APU coatedITMLC coated ess
/ m
20
ZMG232L coated
aleth
ickne
10
Oxid
e sca
040008000120000
Thickness of oxide scales : ZMG232 > CroFer22APU > ITM14
Time / h
© Fraunhofer IKTS
Oxidation behaviourofHT steelscoatedvs. uncoatedWeightgainafteroxidationat850°Cinair Weight gain after oxidation at 850 C in air
15Crofer22APU uncoatedITMLCd
10 cm-2
ITMLC uncoatedZMG232L uncoatedCrofer22APU coatedITMLC coatedZMG232Ltd 10
ain/ m
g cZMG232L coated
5
Weig
ht
ga
04000800012000
0
W
Weight gain: ZMG232>CroFer22APU>ITM14
04000800012000Time / h
© Fraunhofer IKTS
Oxidation behaviourofHT steels
ComparisonWeightgainandScalethicknessforZMG232L ComparisonWeightgainandScalethicknessforZMG232L
1540 WeightGainScaleThickness
Oxide scale thickness
10
30
g/cm 2
ess/ μm
10
20
ghtGain
/ mg
Scale
Thickne
5
10 Weig
Oxide S
800h3200h6400h12000h
Realoxidation: idli
04000800012000
0
04000800012000
0
Time / h
x=kt1/2x=ktn
Real oxidation: No parabolic progression:
Oxide scale gainTheory (Wagner’s law):
© Fraunhofer IKTS
Problem solution: Protective coatings
In situ formationfromthebasematerial oran additional layer
Requirements:
•dense
Result:
•Inhibitionofoxidescalegrowth
•Good adhesion
•Thermalstablility
•PreventionofCrevaporation
ElilbThermal stablility
•chemical compatibility withother SOFC stack components
•Electricalcontactbetweenstackcomponents
•High electronic conductivity
© Fraunhofer IKTS
Influence of protective layers on interconnect properties
PorousperovskiteLSMC roll-coatinglayer
Crofer22APU
after 12000h oxidationZMG232L
after12000hoxidation after 12000h oxidation
Breakawayoxidationwith& withoutprotectivelayer
ZMG232Lafter12000hat850oCwith4thermalcycles
© Fraunhofer IKTS
ZMG232L after 12000 h at 850 C with 4 thermal cycles
Contents
Interconnects for SOFC
High temperature steels and alloys for interconnects
Evaporation of Chromium and Poisoning of electrodes
Formationofoxidescalesoninterconnects Formation of oxide scales on interconnects
Protective coatings on interconnects
High Chromium und temperature alloys
© Fraunhofer IKTS
SchematicclassificationandselectedpropertiesofthesteelsforSOFC application
FeCTE increases
AlloyCTE30…800 °C[10-6K-1]
Chromium-based(CFY)
10,0 …11,0
Fii110125
Austeniticalloys
es do
wn
Stre
ng
thg
Ferritic11,0…12,5
Austenitic18,0…20,0
Iron-Nickel15,0…20,0 Price go
e
go
esu
p
Nickel-based14,0…19,0
CrNi
Higheroperationtemperaturesupto900°C
source: S.Megel, Dissertation, KathodischeKontaktierungin planarenHochtemperatur-BrennstoffzellenStuttgart:IRBFhGVerlag2009p168
Higher operation temperatures up to 900C
Longer operating lifes> 20.000h
© Fraunhofer IKTS
Brennstoffzellen, Stuttgart.: IRB FhGVerlag, 2009, p. 168.
Schema von Plannseezur pulvermetallurgischen HtllCFYMtilfhlth Herstellung von CFY-Material fehlt noch
© Fraunhofer IKTS
Advantages of SOFC stacks assembled with
CFYinterconnect+ESCcellsvsferriticinterconnect+ASCcells
Long lifetime and robustness in Reduction-Oxidation-and thermal-cyclings
CFY interconnect + ESC cells vs. ferriticinterconnect + ASC cells
Thermal expansion of ESC (8YSZ, 10SCSZ) fits to CFY interconnect
Wide range in operating temperatures (Tmax= 900…920°C)
LttditdthihthldtiitfCFYll Lower temperature gradient due to higher thermal conductivity of CFY-alloy
Lower cost due to economics of scale
© Fraunhofer IKTSQuelle: Plansee
Cost reduction of CFY-based interconnect production
Powdermetallurgicalproductionprocess
CFY/ICpieces CFYICCosts
-Powder metallurgical production process
-Near net shaping Low cost post-processing
100,0
1E+09 120
CFY/ICpieces(number of pcs.)
CFY-IC-Costs(arbitrary units)
1 Bio.
150 Mio.
4-5 GWSOFC
100,0
10000000
100000000
80
100
10 Mio.
100 Mio.
15 Mio.
40-50 MWSOFC
400-500 MWSOFC
Interconnects designed by
50,0
100000
1000000
40
604-5 MWSOFC
100,000
1 Mio.
150,000
1.5 Mio.
25,0
12,56,03,0
1000
10000
0
2010,000
1,500
15,000
1000 020042006200820112015> 2020
1000
Tenfold increase of pieces of interconnect
© Fraunhofer IKTS
p
cost reduction of 50%
Conclusions
Formation and growth of the oxide scale during operation at elevated temperatures is the main process for the degradation and long-term stabilityofhighchromiumferriticalloysinSOFCstacks stability of high chromium ferriticalloys in SOFC stacks
Even simple porous protection layers inhibit remarkably the oxidation processoftheinterconnectmaterial process of the interconnect material
Spinelsare most suitable materials for effective low-cost protection layerswhichcanbealsousedascontactintermediateatthecathodesideofthe which can be also used as contact intermediate at the cathode side of the cell
Optimally matched combination of interconnect and protection pyplayer materials is decisive factor to guarantee the long-term operation of the SOFC stack
Ferriticsteelslimited operationtemperature(850°C) andlifetime(<20.000h)
Cr-basedalloyHigher operationtemperatureandlifetime>20.000h
© Fraunhofer IKTS
