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Computational Design and Discovery of Ni-
based Alloys and Coatings:
Thermodynamic Approaches Validated by
Experiments
Bi-Cheng Zhou (Presenter), Austin Ross, Greta Lindwall,
Xuan L. Liu, Zi-Kui Liu (PI)
Department of Materials Science and Engineering
The Pennsylvania State University, University Park, PA 16802
Thomas Gheno, Brian Gleeson
Department of Mechanical Engineering and Materials Science
University of Pittsburgh, Pittsburgh, PA 15261
1
DOE contract No.: DE-FE0024056
2016 Crosscutting Research & Rare Earth Elements Portfolios Review
April 22, 2016 • Pittsburgh, PA
Outline
• Background
• Project Objectives and Tasks
• Approach
• ProgressI. Thermodynamic modeling of Ni-Hf, Ni-Al-Hf,
and Ni-Cr-Hf
II. Prediction of Hf tolerance in NiCrAl bond coat alloys
III. Preliminary results on the effect of Y
• Future work
• Acknowledgement
2
3
Extrinsic Al2O3 scale growth desired for the protection against high
temperature corrosion
Alumina Scale Formation on Alloys
Gleeson, B. (2010). In Shreir’s Corrosion (pp. 180–194). Elsevier.
4
Effects of Reactive Elements (RE) on Alumina
Scale Formation on Alloys
P.Y. Hou, “Impurity effects on alumina scale growth,” J. Am. Ceram. Soc., 86 (2003) 660.
Effects on
Comparisons kp Grain size
Outward transport
Inference
Fe, Ni-based
with RE vs. Without Down 2× Down 1.5-2× Down 4×
RE reduces DbAl by 4×,
has little effect on DbO
RE = Hf, Y, Zr, La, …
Alloy
Al2O3 Scale
Oxygen
-2Ob-2Ol
3Alb3All
Al2O3 scale growth is
dominated by grain-
boundary diffusion at the
temperatures of interest
5
Isothermal Oxidation Kinetics at 1150oC Single Doped : Hf vs. Y
-0.05Y
Ni-20Al-5Cr
-0.1Hf
Base composition (at.%): Ni-20Al-5Cr
0.0
0.3
0.6
0.9
1.2
1.5
0 20 40 60 80 100
Oxidation time, hours
Weig
ht
ch
an
ge,
mg
/cm
2
Ni-20Al-5Cr base
-0.05Y
-0.1Y
-0.05Hf
-0.1Hf
1150oC
6
∆G
˚, k
cal/
mo
l O2 -80
-120
-100
Al2O3
HfO2
500 1000 1500 2000
Temperature, K
aAl = 1
aHf = 1
1150ºC 3Hf + 2Al2O3 → 3HfO2 + 4Al
In order to suppress HfO2:
Gº = -RT × lnKeq and K = aAl
4
aHf3
must have K < Keq
Thermodynamic considerations of
oxidation
Large composition space of bond coat alloys: Ni-Al-Co-Cr-Si-Hf-Y
Control the Hf activity aHf in the alloys is key!
Project Objectives
• Develop a thermodynamic database for accelerated
design of Ni-base alloys and coatings:
Ni-Al-Co-Cr-Si-Hf-Y
• Study effects of reactive elements on the phase stability
and oxide scale formation of bond coat alloys: Hf and Y
additions to Ni-systems
• Experimental verification of thermodynamic predictions
• Assist in the development of the automated
thermodynamic modeling tool (ESPEI)
8
8
Modeling Approach - CALPHAD
Phase diagrams,
direct applications
Thermochemical data: enthalpy,
entropy, heat capacity, activity…
Phase equilibria data: liquidus,
solidus, phase boundary/composition
Gibbs energy
(parameterized)
Fewer data points supplemented by
first-principles calculations
Experimental data plenty, hard to
predict using first-principles
Pure elements Binary Ternary Multi-component
http://www.calphad.org
Practical
applications
9
o The CALPHAD framework requires data that is difficult to access with
experimental work (stable & unstable phases)
o First-principles couples with CALPHAD Naturally!
o Density Functional Theory (DFT) is an efficient way to calculate the
ground state energies of condensed matter systems
First-principles methodology
Shang et al. (2010) Computational Materials Science
approximates
interactions
within the crystalline lattice
for calculations
Properties:
-Ground state
energy of a lattice
-Total energies of
different states
-Finite temperature
properties
Input Output
Efficient! Fewer calorimetric experiments, access metastable states
10
Ni-Al Ni-Cr Ni-Co Ni-Si Ni-Hf Ni-Y Al-Cr
Al-Co Al-Si Al-Hf Al-Y Cr-Co Cr-Si Cr-Hf
Cr-Y Co-Si Co-Hf Co-Y Si-Hf Si-Y Hf-Y
No description availableModeled, compatible descriptions Modeled/Partly modeled
Phase I
Ni-Al-Cr-Co-Si-Hf-Y
Ni-Al-Cr Ni-Al-Co Ni-Al-Si Ni-Al-Hf Ni-Al-Y
Ni-Cr-Co Ni-Cr-Si Ni-Cr-Hf Ni-Cr-Y
Ni-Co-Si Ni-Co-Hf Ni-Co-Y
Ni-Si-Hf Ni-Si-Y
Ni-Hf-Y
Ni-containing ternary systems
Prioritized systems to model for studying of the Hf and Y effect
C
11
• CALPHAD self-consistency and the possibility to
extrapolate to multicomponent systems
A BD
A-BA-C
A-D
B-C
B-D
C-D
A-B-C
A-B-DA-C-D
B-C-D
ChallengeRevisions of lower order systems
re-modeling of higher order
systems
Unary
Binary
Ternary
ESPEIExtensible, Self-optimizing Phase
Equilibrium Infrastructure
• Semi-automated model parameter
optimization
• Statistical analysis of results
• Reusable storage of “raw” data for
potential remodeling
• S. Shang, Y. Wang, Z-K. Liu
Magnesium Technology (2010)
• www.materialsgenome.com
Partly financed by DOE
12
I. Thermodynamic modeling of Ni-Hf, Ni-Al-Hf, and Ni-Cr-Hf
Objectives
o Phase stabilities in base alloys: Al-Cr-Ni + Hf additions
Al-Cr Al-Hf Al-Ni Cr-Hf Cr-Ni Hf-Ni
Al-Cr-Hf Al-Cr-Ni Al-Hf-Ni Cr-Hf-Ni
Al-Cr-Hf-Ni
13
DFT
N/A
Literature
Ni-Hf thermodynamic re-modeling
• Built upon the previous modeling work by Tao Wang et al. (2001) on Ni-Hf
• Remodeling with new data• DFT data for B2 phase
• DFT data for intermetallic compounds
• DFT SQS data for fcc and bcc solid solution
• EPMA data for Hf solubility in Ni
• EPMA data for phase stability of compounds
• Optical microscopy, DSC and XRD data on B2 Hf50Ni50
14
PSU
Pitt
Ni-Hf DFT calculations
Ni Ni5Hf Ni7Hf2 Ni3Hf-L12 𝜶-Ni3Hf Ni21Hf8
Ni7H3 Ni10Hf7 X1Hf1-B33 NiHf-B2 X1Hf2-C16 BCC_A2
Hf
15
Finite Temperature
DFT
0K DFT
No DFT
Previous modeling from Tao Wang et al. (2001) Z. Metallkd. 92 (2001) 5
16
Ni-Hf: thermodynamics
-6
-5
-4
-3
-2
-1
0
104
En
thal
py o
f F
orm
atio
n, J/
mo
l-at
om
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
T=298.15 K
DFT – HfNi3, HfNi
on convex hull
Selhaoui, calorimetry
Bencze, KEMS
Guo, calorimetry
Levy, DFT
T=1423.15 K
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Act
ivit
y
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
Ni Hf
T=1418.15 K
Bencze & Hilpert
(1996) - Knudsen
cell effusion mass
spectrometry
17
Ni-Hf: fcc phase
-6
-5
-4
-3
-2
-1
0
1
104
En
thal
py o
f M
ixin
g, J/
mo
l
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
fcc
γ' fcc+γ'
DFT ()
DFT-SQS (●)
18
Ni-Hf: bcc phase
-6
-5
-4
-3
-2
-1
0
104
En
thal
py o
f M
ixin
g, J/
mo
l-at
om
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
bcc-A2
B2
300
600
900
1200
1500
1800
2100
2400
2700
3000
Tem
per
atu
re [
K]
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
bcc-A2
B2
B2+bcc-A2
DFT ()
DFT-SQS (●)
19
800
900
1000
1100
1200
1300
1400
1500
1600
TE
MP
ER
AT
UR
E_
KE
LV
IN
0 5 10 15 20 25 30
10-3
MOLE_FRACTION HF
Calculated Hf solubility in fcc Ni
Present workHajjaji
ReinbachWangSvechnikov
fcc
fcc+Ni5Hf
fcc+liquid
Previous
modeling in the
literature
Current modeling
Calculated Ni-Hf phase diagram
20
300
600
900
1200
1500
1800
2100
2400
2700
Tem
per
atu
re [
K]
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Hf
HfN
i 5
HfN
i 3H
f 2N
i 7
Hf 3
Ni 7
Hf 7
Ni 1
0
Hf 9
Ni 1
1
HfN
i
Hf 2
Ni
bcc
hcp
B2
fcc
Liquid
HfN
i 3(H
)
Hf 8
Ni 2
1
New cast alloys - Ternaries
21
Micrographs, 1100 °C
Al-Hf-Ni
Cr-Hf-Ni
22
New cast alloys - Ternaries
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0 0.1 0.2 0.3 0.4 0.5
Mole Fraction Hf
Al-Hf-Ni
Cr-Hf-Ni
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0 0.1 0.2 0.3 0.4 0.5
Mole Fraction Hf
1000 °C
1100 °C
1200 °C
Model solubility of Ni7Hf2
Ni7Hf2
Ni7Hf2 new sublattice model to
include Al solubility
23
Compound Prototype Structure Space Group
Ni7Hf2 Zr2Ni7 C2/m
Hf
Ni No Atom Multiplicity Wyckoff
1 Ni 8 j
2 Ni 8 j
3 Ni 8 j
4 Hf 4 i
5 Ni 4 i
6 Hf 4 i
New Sublattice Model(Hf,Ni)2(Al,Ni)7
Assumption: all Al goes into the Ni site
DFT endmembers:(Hf)2(Ni)7, (Hf)2(Al)7,(Ni)2(Ni)7, (Ni)2(Al)7Al,Ni Interaction parameter
from experiments
Not consideringConsidering Al solubility in Hf2Ni7
T=1100 ̊CNi7Hf2 Ni7Hf2
Calculated Al solubility in Ni7Hf2
Experimental
tie-triangle
’ ’
26
0
5
10
15
20
25
30
at.
% A
l, C
r
900 1000 1100 1200
T (°C)
γ
Cr
Al
0
0.2
0.4
0.6
0.8
1.0
1.2
at.%
Hf
Hf
0
5
10
15
20
25
30
at.
% A
l, C
r 900 1000 1100 1200
T (°C)
at.%
Hf
0
0.2
0.4
0.6
0.8
1.0
1.2
γ’
Cr
Al
Hf
Phase compositions in NiCrAl-Hf alloys
Experiments
Current thermodynamic modeling
□ ∆
27
26
II. Prediction of Hf tolerance in NiCrAl bond coat alloys
27
∆G
˚, k
cal/
mo
l O2 -80
-120
-100
Al2O3
HfO2
500 1000 1500 2000
Temperature, K
aAl = 1
aHf = 1
1150ºC 3Hf + 2Al2O3 → 3HfO2 + 4Al
In order to suppress HfO2:
Gº = -RT × lnKeq and K = aAl
4
aHf3
must have K < Keq
Thermodynamic considerations of
oxidation
Large composition space of bond coat alloys: Ni-Al-Co-Cr-Si-Hf-Y
Control the Hf activity aHf in the alloys is key!
Three Ni-Al-Cr + 0.1 at. % Hf alloys
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0 0.1 0.2 0.3 0.4 0.5
Mole Fraction Cr
1000 °C1100 °C1200 °C
Calculated Al-Cr-Ni isothermal section
Predicted HfO2 formation “boundary” at 1000 °C
Oxidation of NiCrAl-Hf alloys
HQ7 HQ8 HQ9
1000 °C γ-γ’ γ-γ’ γ-γ’
1100 °C γ γ-γ’ γ-γ’
1200 °C γ γ γ
30
0
0.1
0.2
0.3
0.4
0.5
0.6
Hf
co
nte
nt
for
HfO
2fo
rma
tio
n, a
t.%
0 5 10 15 20 25 30
Cr concentration, at.%
23%Al
21%Al
19%Al
17%Al
15%Al
13%Al
𝛾
𝛾′
𝛾 + 𝛾′
B2 + 𝛾′B2 + 𝛾 + 𝛾′
B2 + 𝛾
• No Hf oxidation (traces present in middle of scale probably left from
transient stage)
• Localized Hf oxidation (this is a subjective call)
Hf not oxidized
Hf not oxidized
• Hf oxidation
Determination of whether Hf oxidized or not
31
Note: all three alloys contained 0.1 at. % Hf
Predicted HfO2 formation “boundary” at 1200 °C
Oxidation of NiCrAl-Hf alloys
7.5Cr-13Al
7.5Cr-17Al
13Cr-17Al
1200 °C
HfO2 pegs
32
0
0.1
0.2
0.3
0.4
0.5
0.6
Hf
co
nte
nt
for
HfO
2fo
rma
tio
n, a
t.%
0 5 10 15 20 25 30
Cr concentration, at.%
23%Al
21%Al
19%Al
17%Al
15%Al
13%Al
𝛾
𝛾′
𝛾 + 𝛾′
B2 + 𝛾′B2 + 𝛾 + 𝛾′
B2 + 𝛾
• Effect of temperature: tolerance reduced (larger driving force
for HfO2 formation) with increasing temperature
alloy HQ8 1100 °C 1200 °C
less zones with no oxidation
less zones with no oxidation
alloy HQ9 1000 °C 1100 °C
γ-γ’
γ
γ-γ’
γγ-γ’
γ
33
1000 °C
1100 °C
1200 °C
HQ8: Ni-8Cr-17Al-0.1HfHQ10: Ni-8Cr-17Al-0.05Hf
γ-γ’
γ
γ-γ’
γ
γ
γ-γ’
γ
γ-γ’
γ
γ
• Effect of Hf (more Hf promotes HfO2 formation)
34
• Effect of Cr (prediction: Hf tolerance decreases when Cr increases)
1000 °C
1100 °C
1200 °C
HQ8: Ni-8Cr-17Al-0.1Hf HQ9: Ni-13Cr-17Al-0.1Hf
γ-γ’
γ
γ-γ’
γ
γ
γ-γ’
γ
γ-γ’
γ
35
34
III. Preliminary results on the effect of Y
Ternary Assessments of Y-containing systems in Literature
35
Base Al-Co-Cr Al-Co-Ni Al-Cr-Ni Co-Cr-Ni
X1-X2-Y Al-Co-Y Al-Cr-Y Al-Ni-Y Co-Cr-Y Co-Ni-Y Cr-Ni-Y
X1-X2-Hf Al-Co-Hf Al-Cr-Hf Al-Ni-Hf Co-Cr-Hf Co-Ni-Hf Cr-Ni-Hf
X1-X2-Si Al-Co-Si Al-Cr-Si Al-Ni-Si Co-Cr-Si Co-Ni-Si Cr-Ni-Si
X1-Hf-Y Al-Hf-Y Co-Hf-Y Cr-Hf-Y Ni-Hf-Y
X1-Hf-Si Al-Hf-Si Co-Hf-Si Cr-Hf-Si Ni-Hf-Si
X1-Si-Y Al-Si-Y Co-Si-Y Cr-Si-Y Ni-Si-Y
Additions Hf-Si-Y
Assessment available
Assessment not found
Good from binaries
Assessment under investigation
Ni-Y
36
Du, Z., & Lü, D. (2005). Thermodynamic modeling of the Co–Ni–Y system. Intermetallics, 13(6), 586–595.
200
400
600
800
1000
1200
1400
1600
1800
2000
Te
mp
era
ture
(K)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Mole Fraction Y
1
1:L12_FCC#1
2
2:M17M5YX#1
33:LIQUID#1
1
32
2
4
4:M17M5YX#234
35
5:M4Y#136 6:M7Y2#1
3
7
7:M3Y#1
3
8
8:M2Y#1
3
9
9:MY#1
310
10:M2Y3#1
3
11
11:MY3#1
3
12 12:HCP_A3#1
313
13:BCC_B2#1
1312
12
1110
11
109
89
87
76
56
45
31313
YNi
Y Solubility in Ni
37
600
800
1000
1200
1400
1600
1800Te
mp
era
ture
(K
)
0 2 4 6 8 10 12 14 16 18 20
10-4
Mole Fraction Y
1
1:L12_FCC#13
3:LIQUID#1131
Ni
Beaudry, B. J., Haefling, J. F., & Daane, A. H. (1960). Acta Crystallographica, 13(9), 743–744.
Huang, J., Yang, B., Chen, H., & Wang, H. (2015). Journal of Phase Equilibria and Diffusion, 36(4), 357–365.
Interactions in the fccphase from Huang et al. (2015).
More work needs to be done to determine the Ni-Y interaction in fccphase.
fcc
fcc + Y2Ni17
38
Stability of Y2O3
Ni-10Cr-xAl-zY 1000̊C
x=0.25x=0.1
Alloy+Al2O3+Y2O3
x=0.25
x=0.1
Alloy+Y2O3
𝑃 𝑂2
𝑁 𝑌
𝑁 𝑁𝑖 + 𝑁 𝐴𝑙 + 𝑁 𝐶𝑟 + 𝑁(𝑌)
Hf tolerance
concept not present:
Y2O3 always more
stable at low PO2
39
Oxidation of Ni-Al-Cr-Y Alloys at 1200̊C: possible correlation between oxide scale
formation and yitrrides formation
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Wt%
Y
0 5 10 15
Wt% Al
1.6 wt percent Cr9 wt percent CrImproved scale growthNominal scale growth
Kvernes, I. A. (1973). Oxidation of Metals, 6(1), 45–64. Yittrides tolerance
curves
Future Works in Phase II
• Continue to investigate the Y and Si effects on oxide scale formation in Phase II
• Study the Hf+Y co-doping effects on oxide scale
• Planned publications so far:1. Hf-Ni Binary thermodynamic modeling
2. Al-Hf-Ni, Cr-Hf-Ni Ternaries thermodynamic modeling
3. Al-Cr-Hf-Ni prediction + Oxidation experiments
• The further development of ESPEI for automation of thermodynamic modeling
40
Acknowledgements
• Project manager: Jason Hissam
• Funding from DOE-NETL: DE-FE0024056
• High performance computing resources on XSEDE, NERSC and the LION-X and CyberStar clusters at Penn State
41
Thank you for your attention.
Any questions?