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ORNL is managed by UT-Battelle for the US Department of Energy
DOE Award Number: FEAA114Period of Performance: Oct. 2013 - Sep.2018Presentation: March 22nd, 2017 (in Computational Materials)
Advanced Alloy Design Concepts for High-Temperature Fossil Energy ApplicationsPI: Yukinori Yamamoto Oak Ridge National Laboratory, Oak Ridge, TN 37831E-mail: [email protected]
Co-investigators:Bruce A. PintOak Ridge National Laboratory, Oak Ridge, TN
Sudarsanam Suresh Babu, Benjamin Shassere*, Chih-Hsiang (Sean) KuoUniversity of Tennessee, Knoxville, TN(*Currently at Oak Ridge National Laboratory)
2017 Crosscutting Research Portfolios ReviewPittsburgh, PA, March 20-23, 2017
2 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
AcknowledgementsProgram management: Vito Cedro (NETL), Pete Tortorelli, Hiram Rogers (ORNL)
Scientific advice and support: Mike Brady, Muralidharan Govindarajan, Roger Miller, Zhiqian Sun, Donovan Leonard (ORNL), Bernd Kuhn (Forschungszentrum Jülich GmbH, Germany),Kazuhiro Kimura (National Institute for Materials Science, Japan)
Technical support: Cecil Carmichael, Dave Harper, Greg Cox, Dustin Heidel, Kevin Hanson, Daniel Moore, Tom Geer, Victoria Cox, Eric Manneschmidt, Jeremy Moser, Mike Stephens, George Garner, Doug Kyle, Brian Sparks (ORNL)
Research sponsored by the Crosscutting Research Program, Office of Fossil Energy, U.S. Department of Energy
3 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Project Goals and ObjectivesGoals: To identify and apply breakthrough alloy design concepts and strategies for incorporating improved creep strength, environmental compatibility/resistance, and weldability into three classes of alloys (ferritic, austenitic, and Ni-base) intended for use as heat exchanger tubes in fossil-fueled power generation systems at higher temperatures than possible with currently available alloysObjectives: To develop and propose new creep-resistant, “alumina-forming”, cost-effective structural materials with guidance of computational thermodynamic tools• Milestones (FY2017):1. Complete intermediate-term oxidation and creep testing of scale-up heats of “model alloy” (Met)
2. Submit a journal paper summarizing the new FeCrAl alloy design study (In Progress)
3. Initiate computational screening of next generation advanced alumina-forming austenitic and Ni-base alloys for improved strength and corrosion resistance (In Progress)
4 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Presentation Outline• Backgrounds/Motivation:
– Concepts of “Advanced Alloy Design”– High-Cr containing FeCrAl “ferritic” alloy development
• Update on FY16/17– Effect of alloying on Laves-phase solvus and stability– Creep property evaluation– Oxidation/ash-corrosion tests– Scale-up efforts
• Summary • Future Activities
5 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Backgrounds: Advanced Alloy DesignHigh-temp. Strength
Oxidation/Corrosion
https://mts.com/en/products/industry/materials-testing/index.htmhttp://www.ccj-online.com/prioritization-of-issues-improves-hrsg-reliability-performance/`
High-Cr containing FeCrAl ferritic alloy(Fe-30Cr-3Al base, wt/%)
Weldments
Weld
Type IV failure (at fine grained HAZ)
Source: ETD Ltd.
Base(F-M steel)
Strong demands on new high-temperature materials with improved properties for upper limit temperatures higher than that of the materials currently in service;
– High-temperature strength (tensile, creep)– Environmental compatibilities (oxidation, corrosion)– Minimized weld-related issue for final components– RT toughness (Charpy)– Processibility (including microstructure control)– Inexpensive materials cost (raw elemental costs,
process routes, etc.)
6 Advanced Alloy Design Concepts for High-temperature Fossil Energy ApplicationsF/FM steels Austenitics Ni alloys
Relat
ive ra
w m
ater
ial co
st
(x4~6)
(x ~20)
Target Materials/ ApplicationsThree different grades of structural materials that are currently available for use by the US electric utility industry: 1) Ferritic steels for temperatures up to 600 °C, with ferritic-martensitic versions (F-M steels)
having increased strength up to 600-620 °C;
2) Austenitic stainless steels with strength and environmental resistance up to 650 °C; and
3) Ni-base alloys for temperatures > 700 °C.
(CSEF steels: >3.6Mlbs. for piping and boiler tubing)
Material tonnage
Alstom USC and AUSC Power Plants – J. Marion - NTPC/USAID Int. Conf. SC Plants - New Delhi, India, 22 Nov. 2013 – P 8
7 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Why High Cr Containing FeCrAl Ferritic Alloy?• High surface protection in both steam and ash-corrosion environments• Less thermal expansion and high thermal conductivity• Suppress brittle σ-FeCr formation by Al additions• No Type IV failure because of no BCC-FCC transformation during welding
Fe-19Creq-15Nieq
Fe-30Creq
Ref. Welding Research Supplement (1982)
Mean coefficient of thermal expansion
at 750 °C
(BCC-Fe)
(σ-FeCr)
Fe
Cr
Al
Fe-30Cr-3Al
Fe-Cr-Al ternary alloy phase diagram
Ref. ASM international, Ternary alloy phase diagrams
Fe Cr→
Ref. ASM international, Binary alloy phase diagrams
Fe-Cr binary alloy phase diagram
(F-M steels) (fully ferritic alloys)M23C6, MX
‘-Fe (martensite)
-Fe (ferrite)
(*premature failure at HAZ)
Type IV failure*
Gr. 91Weld
8 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
What is the Challenge in High Cr Containing FeCrAlFerritic Alloy?• Poor high-temperature strength due to BCC matrix• Rapid grain coarsening causes poor ductility at low temperature
Fe-30Cr-3Al(Rolled at 300°C + Annealed at 1100°C) 500µm
OMNo optimization
(BCC-Fe matrix)
Fe-30Cr-3Al + Nb, Zr(Rolled at 300°C + Annealed at 1200°C)
Fe-30Cr-3Al +W, Nb, Si(Aged at 700°C)
Laves-Fe2Nb
1µm500µm
OM SEM-BSEAfter optimization
http://www.geocities.jp/ohba_lab_ob_page/structure5.html
Fe: Nb:
C14: Laves-Fe2Nb
→ Use alloying additions for GS stability and strengthening (e.g. Nb for Laves-phase formation)
9 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Alloy Development in Progress• 1st series: Fe-30Cr-3Al with (0~2)Nb-(0~0.3)Zr (in wt.%)
– Optimization of thermo-mechanical treatment– Tensile test (RT~800°C)– Oxidation test (800°C, in air + 10%H2O)– Ash corrosion test (700°C, in ash + corrosive gas)– Creep-rupture test (650~700°C, 70~100MPa)
*Used Bird-Mukherjee-Dorn (BMD) model
2 ln
Calc. minimum creep-rate map
Ash-corrosion test at 700°C for 500h
(Fe-30Cr base)1Al-2Nb
(Fe-30Cr base)3Al-2Nb
Ash: 30%Fe2O3-30%Al2O3-30%SiO2-5%Na2SO4-5%K2SO4Gas: 61%CO2-30%H2O-3%O2-0.45%SO2
2μm
TEM-BFI
Laves in matrix
• 2nd series: Fe-30Cr-3Al with (0.5~2)Nb + W, Mo, Ti, and Y– BCC solvus temperature control– Size stability of Lave-phase particle at 700°C– Oxidation/Ash-corrosion resistance – Property evaluation– Scale-up effort
10 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Major Concerns in FY17
• Effect of third element addition on microstructural stability, mechanical properties, and oxidation/ash-corrosion resistance:– Nb, W, Mo, and Ti (Laves-phase forming elements)– Mn, Si, C (simulate engineering alloys with the level of industrial impurities)
• Scale-up efforts of high-Cr FeCrAl alloy
11 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Experimental Procedure• Alloys to be evaluated:
– Fe-30Cr-3Al base with (or without) Nb, Si, W, Mo, Ti, Y, Mn, and C, wt.%
– Used thermodynamic computational tool (JMatPro, v.8-9) for downselection
• Lab-scale heat preparation:– Arc-melt and drop-cast the bar ingots (13 x 25 x 125 mm)
• Thermo-mechanical treatment:– Homogenization, forging, rolling, annealing– Water-quenching
• Microstructure analysis:– OM, SEM
• Property evaluations:– Creep, oxidation, ash-corrosion
Fe-30Cr-3Al-0.2Si base alloys
1Nb
2Nb1Nb-2W
1Nb-2Mo
1Nb-1Ti
BCC-Cr (α-Cr)
LiquidBCC-Fe700ºC
Fe2Nb-Laves
Annealed at 1200°C (SEM-BSE)
10µm
2Nb alloy 1Nb-2W alloy
Laves-Fe2Nb
Hot-forging (ORNL)
25mm
Lab-scale ingot (ORNL)
12 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Impact of “Third Additional Elements” on Microstructure
• Fine particle size maintained even after 10,000h at 700°C
10µm
10,000h@700ºC168h@700ºC 1,000h@700ºC
10µm
Fe-30Cr-3Al-1Nb-2W
Fe-30Cr-3Al-1Nb-1Ti10,000h@700ºC168h@700ºC 1,000h@700ºC
Growth kinetics of Laves phase
50
500
100 1000 10000
Mea
n pa
rtic
le s
ize*
, nm
Aging time at 700°C, h
0.5Nb-2TI1Nb-1Ti1Nb-1.5Mo1Nb-2W2Nb
1Nb-2W
1Nb-1.5Mo
1Nb-1Ti
0.5Nb-2Ti
100
(Fe-30Cr-3Al base)
at 700ºC (initial condition: HR+Ann@1200ºC)
2Nb (1Nb-1Nb)
200
300
400
*assumed the normal distribution
13 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
0
5
10
15
20
0 500 1000 1500 2000 2500
Cre
ep s
trai
n, %
Time /h
700°C/70MPa
2Nb
Third Element Addition Was Effective As Expected
0
5
10
15
20
0 500 1000 1500 2000 2500
Cre
ep s
trai
n, %
Time /h
700°C/70MPa
1Nb-2W
1Nb-0.5Ti(2.5 mole %)
(2.8 mole %)(3.3 mole %)
Creep rate: 1.3 x 10-9/s2.5 x 10-9/s4.7 x 10-9/s
BCC-Cr (α-Cr)
LiquidBCC-Fe
Fe2Nb-Laves
2Nb1Nb-2W
1Nb-0.5Ti
SEM-BSE
1μm
PrecipitateFree Zone
• Grain Boundary Zone Strength Factor:Grain boundary precipitate coverage
Width of precipitation free zoneB. Shassere et al. (to be submitted)
14 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
0 1 2 3 4
Cre
ep-r
uptu
re li
fe, h
Laves phase at 700ºC, mole%
Model alloys
700ºC/70MPa
0Nb
1Nb
2Nb1Nb-2W
1Nb-0.5Ti
Creep-rupture life vs. Laves phase
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
0 1 2 3 4
Min
. cre
ep ra
te, /
s
Laves phase at 700ºC, mole%
Model alloys
700ºC/70MPa
Min. Creep Rate / Creep-rupture Life Depend On Fraction of Laves Phase Precipitates
Min. creep rate vs. Laves phase
(Fe-30Cr-3Al base) (Fe-30Cr-3Al base)
0Nb
1Nb
2Nb1Nb-2W
1Nb-0.5Ti
Creep-rupture life vs. Min. creep-rate
15 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Moving toward Engineering Alloys
• Optimized the combination of Nb, W, Mo, and Ti: – Maximize Laves phase formation combined with reasonably low BCC solvus
temperature (for Laves phase)
• Considerations of industrial quality chemistry:– Mn, Si, and C were intentionally added to simulate commercial steels– P, S, and N still need to be minimized for better weldability and oxidation
resistance
16 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
900
1000
1100
1200
1300
0 2 4 6 8
BC
C s
olvu
s, ºC
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb
(Fe-30Cr-3Al-1Nb base)
Nb + Mn, Si, C
0
1
2
3
4
5
6
7
8
0 2 4 6 8
Lave
s at
700
ºC, m
ole
%
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb
Nb + 0.4Mn, 0.15Si, 0.03C
(Fe-30Cr-3Al-1Nb base)
900
1000
1100
1200
1300
0 2 4 6 8
BC
C s
olvu
s, ºC
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
+Ti +Mo +W
+Nb
0
1
2
3
4
5
6
7
8
0 2 4 6 8
Lave
s at
700
ºC, m
ole
%
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
+Ti+Mo +W
+Nb
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
0
1
2
3
4
5
6
7
8
900 1000 1100 1200 1300
Lave
s at
700
ºC, m
ole
%
BCC solvus, ºC
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
+Ti
+Mo
+W+Nb
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
BCC Solvus Temperature Control
900
1000
1100
1200
1300
0 2 4 6 8
BC
C s
olvu
s, ºC
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
+Ti +Mo +W
+Nb
0
1
2
3
4
5
6
7
8
0 2 4 6 8
Lave
s at
700
ºC, m
ole
%
Additional element, wt.%
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
+Ti+Mo +W
+Nb
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
0
1
2
3
4
5
6
7
8
900 1000 1100 1200 1300
Lave
s at
700
ºC, m
ole
%
BCC solvus, ºC
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + W
+Ti
+Mo
+W+Nb
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
• Ti: < 0.3 wt.% for better oxidation resistance• Mo: < 0.5 wt.% to avoid σ-FeCr or χ-FeCrMo formation
0
1
2
3
4
5
6
7
8
900 1000 1100 1200 1300
Lave
s at
700
ºC, m
ole
%
BCC solvus, ºC
Model, Nb1Nb-Mn-Si-C + Nb + Ti + Mo + WEng. 1Nb+W
+Ti
+Mo
+W+Nb
(Fe-30Cr-3Al-1Nb + Mn, Si, C base)
1Nb-6W, Mo, Ti, Mn, C
1Nb-2W-0.5Mo-0.3Ti + Mn, C
BCC solvus700ºC
Phas
e, m
ole
%
Laves-phase
17 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
0
5
10
15
20
0 500 1000 1500 2000 2500
Cre
ep s
trai
n, %
Time /h
700ºC/70MPa
2Nb1Nb-2W
1Nb-0.5Ti
Improved Creep Resistance by Increased Volume Fraction of Laves-phase Precipitates
0
5
10
15
20
0 500 1000 1500 2000 2500
Cre
ep s
trai
n, %
Time /h
700ºC/70MPa
2Nb1Nb-2W
1Nb-0.5Ti
1Nb-2W (with Mo, Ti, Mn, C)
4.2 x 10-9/s4.7 x 10-9/s
0
5
10
15
20
0 500 1000 1500 2000 2500
Cre
ep s
trai
n, %
Time /h
700ºC/70MPa
2Nb1Nb-2W
1Nb-0.5Ti
1Nb-6W (with Mo, Ti, Mn, C)
1Nb-2W (with Mo, Ti, Mn, C)
3.9 x 10-10/s4.2 x 10-9/s
10µm
Interrupted after 500h testing
1Nb-2W, aged 1000h@700C
10µm
18 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
0 2 4 6 8C
reep
-rup
ture
life
, h
Laves phase at 700ºC, mole%
Model alloysEngineering alloys
700ºC/70MPa
1Nb
1Nb-0.5Ti
1Nb-2W2Nb
1Nb-2W, Mo, Ti
1Nb-6W, Mo, Ti
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E-10 1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04C
reep
-rut
pure
life
, h
Min. creep rate, /s
Model alloysEng. Alloys
700ºC/70MPa
1.E-10
1.E-09
1.E-08
1.E-07
0 2 4 6 8
Min
. cre
ep ra
te, /
s
Laves phase at 700ºC, mole%
Model alloysEngineering alloys
700ºC/70MPa
Creep-rupture life vs. Laves phase
Min. Creep Rate / Creep-rupture Life Depend On Fraction of Laves Phase Precipitates
Min. creep-rate vs. Laves phase
(Fe-30Cr-3Al base) (Fe-30Cr-3Al base)
1Nb
2Nb
1Nb-2W
1Nb-0.5Ti
1Nb-2W, Mo, Ti
1Nb-6W, Mo, Ti
Creep-rupture life vs. Min. creep-rate
19 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
0
0.1
0.2
0.3
0 500 1000 1500 2000 2500
Mas
s ga
in, m
g/cm
2
100h cycle exposure time, h
25Cr-3Al-2Nb
30Cr-3Al-1Nb-0.5Ti
30Cr-3Al-1Nb-2W
30Cr-3Al-2Nb
30Cr-2.6Al-2Nb
9.05x10-6
1.18x10-5
3.32x10-6
6.89x10-6
1.92x10-6
Parabolic rate constant
(mg·cm-2s-0.5 )
Important Role of Al Addition on Oxidation Resistance
• Slow oxidation kinetics indicates protective alumina scale formation
-0.2
0
0.2
0.4
0.6
0.8
1
0 500 1000 1500 2000 2500
Mas
s ga
in, m
g/cm
2
100h cycle exposure time, h
Binary Fe-25Cr
Binary Fe-30Cr
High Cr FeCrAl
Volatarization of chromia scales: 1/2 Cr2O3 + 3/4 O2(g) + H2O(g) = CrO2(OH)2(g) 800ºC, 10% water vapor, 100h cycle
20 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Ash: Al2O3 16.9%, SiO2 22.6%, CaO 0.9%, Fe2O3 7.8%, KOH 1%, TiO2 0.6%, MgO 0.2%, Fe2(SO4)3 19.8%, MgSO4 10.1%, K2SO4 4.8%, Na2SO4 15.1%Gas: Synthetic gas simulating combustion environment in a steam plant (suggested by B&W/EPRI)
Ash-corrosion Tested at 700ºC for 500h
CC05-6AC (#13457)0.70 mg/cm2
CC05-7AC (#13458)0.63 mg/cm2
CC09-3 (#13460)0.68 mg/cm2
CC11-3 (#13463)0.80 mg/cm2
CC13 (#13465)-142.18 mg/cm2
RF25C (#13467)-46.97 mg/cm2
RF30C (#13469)-139.49 mg/cm2
30Cr30Cr-2.6Al-2Nb 30Cr-3Al-2Nb 1Nb-2W 1Nb-0.5Ti 25Cr25Cr-3Al-2Nb
2mm2mm2mm2mm2mm2mm 2mm
30Cr
-2.6A
l-2Nb 30
Cr-3
Al-2
Nb
30Cr
-3Al
-1Nb
-2W
30Cr
-3Al
-1Nb
-0.5T
i
25Cr
-3Al
-2Nb
Fe-3
0Cr
Fe-2
5Cr(Measured from cross section)
21 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Scale-up Efforts (Fe-30Cr-3Al-2Nb-0.2Si-0.12Y)VIM ingot (4” dia.) after HIPing
Forged at 1250ºC
Total ~22”~20”
~8”
Thickness :~0.6”
~22”
~8”
Rolled (and annealed) at 1250ºC
ACWQ
22 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
10
100
20000 21000 22000 23000 24000 25000
Cre
ep s
tres
s, M
Pa
LMP (C=20)
30Cr-3Al-2Nb (small heat_WQ)Gr92Gr91100kh-life temperature
550 650600 700100kh-life temperature, °C
Tested at 650-750°C
10
100
20000 21000 22000 23000 24000 25000
Cre
ep s
tres
s, M
Pa
LMP (C=20)
30Cr-3Al-2Nb (small heat_WQ)30Cr-3Al-2Nb (Scale-up_AC)Gr92Gr91100kh-life temperature
550 650600 700100kh-life temperature, °C
Tested at 650-750°C
~25%
Effect of Cooling Rate after Solution AnnealingAnnealed at 1250ºC+ WQ
Annealed at 1250ºC+ AC
Fe17Y2
(BCC matrix)
Fe17Y2
(BCC matrix)
Fe2Nb
10
100
20000 21000 22000 23000 24000 25000
Cre
ep s
tres
s, M
Pa
LMP (C=20)
30Cr-3Al-2Nb (small heat_WQ)30Cr-3Al-2Nb (Scale-up_AC)Gr92Gr91100kh-life temperatureEng. 1Nb-6W
550 650600 700100kh-life temperature, °C
Tested at 650-750°C
WQAC
23 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Summary
• Effect of third element additions in Fe-30Cr-3Al base alloy on “microstructural stability” and “various high-temperature properties”:– W, Mo, and Ti additions are;
• Effective to lower the BCC solvus temperature• Detrimental to microstructure stability during creep deformation
– The larger volume fraction of Laves phase precipitate, the better for the creep resistance– Oxidation and ash-corrosion resistance are more sensitive to the amounts Cr and Al (and Nb)
than the others
• Scale-up efforts in progress– Move to engineering alloys (based on 1Nb-6W +Mo, Ti, Mn, and C)– Require improvement of better processibility (against thermal shock, etc.)
24 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Future Activities
• Property evaluation the second scale-up heat:– Screening basic properties (tensile, hardness, microstructure)
– Intermediate/long-term creep-rupture test at or above 700ºC
– Ash-corrosion resistance evaluation at 700ºC
– GTAW screening
• New efforts on alumina-forming austenitic steels and Ni-base alloys– Target the applications in various extreme conditions (coking, metal dusting, sCO2, etc.)
– Communications with industrial partners initiated
25 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Thanks
26 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
0
0.1
0.2
0.3
0 500 1000 1500 2000 2500
Mas
s ga
in, m
g/cm
2
100h cycle exposure time, h
25Cr-3Al-2Nb
30Cr-3Al-1Nb-0.5Ti
30Cr-3Al-1Nb-2W
30Cr-3Al-2Nb
30Cr-2.6Al-2Nb
9.05x10-6
1.18x10-5
3.32x10-6
6.89x10-6
1.92x10-6
Parabolic rate constant
(mg·cm-2s-0.5 )
Important Role of Al Addition on Oxidation Resistance
• Slow oxidation kinetics indicates protective alumina scale formation
-0.2
0
0.2
0.4
0.6
0.8
1
0 500 1000 1500 2000 2500
Mas
s ga
in, m
g/cm
2
100h cycle exposure time, h
Binary Fe-25Cr
Binary Fe-30Cr
High Cr FeCrAl
Volatarization of chromia scales: 1/2 Cr2O3 + 3/4 O2(g) + H2O(g) = CrO2(OH)2(g)
0
0.1
0.2
0.3
0 500 1000 1500 2000 2500
Mas
s ga
in, m
g/cm
2
100h cycle exposure time, h
*30Cr-3Al-1Nb-2W-Mo, Ti, Mn, Si, C
*30Cr-3Al-1Nb-6W-Mo, Ti, Mn, Si, C
30Cr-3Al-1Nb-2W
30Cr-3Al-2Nb
*Engineering alloys
6.89x10-6
1.93x10-6
4.23x10-5
2.84x10-5
Parabolic rate constant
(mg·cm-2·s-0.5 )
800ºC, 10% water vapor, 100h cycle
27 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
0
5
10
15
20
0 500 1000 1500
Cre
ep s
trai
n (tr
ue s
tria
n) /%
Time /h
750°C/50MPa
1Nb-2W (w/Mo, Ti, Mn, C)
1Nb-6W (w/Mo, Ti, Mn, C)
Higher Temperature Tests In Progress (750 & 800 °C)
0
1
2
3
4
0 500 1000 1500
Cre
ep s
trai
n (tr
ue s
tria
n) /%
Time /h
800°C/30MPa
1Nb-2W (w/Mo, Ti, Mn, C)
1Nb-6W (w/Mo, Ti, Mn, C)
28 Advanced Alloy Design Concepts for High-temperature Fossil Energy Applications
Scale-up Efforts (Fe-30Cr-3Al-2Nb-0.2Si-0.12Y)VIM ingot (4” dia.) after HIPing
Forged at 1250ºC
Total ~22”
at 1250ºC+ AC
~20”
~8”Thickness :~0.6”
at 1250ºC+ WQ
Thickness :~0.6”
~20”
~8”
at 1000ºC
~26”
~7”
Thickness :~0.6”
Rolledat 800ºC
~10”