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?