NASA Technical Reports Server (NTRS) 20070032921: Measured Activities of Al and Ni in gamma-(Ni) and gamma'-(Ni)3Al in the Ni-Al-Pt System

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Measured Activities of Al and Ni in γ-(Ni) and γ′-(Ni) Al
3
in the Ni-Al-Pt System
Evan Copland
NASA Glenn Research Center / Case Western Reserve University,
Cleveland, Ohio 44135
Abstract
Adding Pt to Ni-Al coatings is critical to achieving the required oxidation protection of
Ni-based superalloys, but the nature of the “Pt effect” remains unresolved. This research
provides a fundamental part of the answer by measuring the influence of Pt on the activities
of Al and Ni in γ-(Ni), γ'-(Ni) Al and liquid in the Ni-Al-Pt system. Measurements have
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been made at 25 compositions in the Ni-rich corner over the temperature range,
T = 1400 – 1750 K, by the vapor pressure technique with a multiple effusion-cell mass
spectrometer (multi-cell KEMS). These measurements clearly show adding Pt
(for X < 0.25) decreases a(Al) while increasing a(Ni). This solution behavior supports the
Pt
idea that Pt increases Al transport to an alloy / Al O interface and also limits the
2 3
interaction between the coating and substrate alloys in the γ-(Ni) + γ'-(Ni) Al region.
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This presentation will review the progress of this study.
National Aeronautics and Space Administration
measured a(Al) and a(Ni) in γ-(Ni) and γ′-(Ni) Al
3
in the Ni-Al-Pt System
E. Copland
Case Western Reserve University / NASA Glenn Research Center
Cleveland, Ohio
MS&T 2007: 9/19/2007 – COBO Center Detroit, Michigan, USA
www.nasa.gov
2
motivation
1.5
γ+γ'-(20Pt) ∼10μm
1
)
2
m β-(15Pt)
c
/ β-(15Pt) γ+γ'-(20Pt)
g
m
( 0.5

t
h
g protective Al O formation
ei 2 3
w β
Δ
0
γ+γ'
-0.5
0 100 200 300 400 500
1h cycles
cyclic oxidation at 1150˚C in air
β-(Pt) coatings (cid:116) γ + γ′-(Pt) coating / alloy
S. Hayashi, S. Ford, D. Young, D. Sortelet, M. Besser, B. Gleeson, Acta Materialia, 2005, 53, 3319.
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measured alloy compositions
phase Ni Al Pt
91.7 8.3 ~
γ 85.0 15.0 ~
80.5 19.5 ~
82.2 14.8 2.0
87.9 10.1 2.0
80.0 15.0 5.0
76.4 13.7 9.9
80.9 9.1 10.0
70.0 12.0 18.0
75.2 6.9 17.9
Knuds6e5n.3 effus9io.8n-cel2l4.9
70.0 5.0 25.0
50.0 ~ 50.0
76.8 23.2 ~
γ′ 75.0 25.0 ~
73.7 27.3 ~
73.6 24.3 2.0
65.8 24.2 10.0
57.9 24.0 18.1
51.1 23.8 25.1
70.8 27.2 2.0
γ-(Ni), γ′-(Ni,Pt) Al and L equilibrium with Al O
3 2 3 63.8 26.4 9.8
54.9 27.0 18.1
(cid:116) Ni-Al-Pt-O system
48.1 26.7 25.2
( at.% ±0.5 )
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thermodynamic measurements
multi-cell KEMS
pressure measurement
+
p(i) = I T S
ik ik
activity measurement
p(i) I
a(i) = = i
po(i) Io
i
p(i) ⎡ p(cid:68)(Au)⎤ I S g(R) ⎡ p(cid:68)(Au)⎤
a(i) = ⋅⎢ ⎥ = i ⋅ Au ⋅ ⋅⎢ ⎥
p(cid:68)(Au) ⎢⎣ p(cid:68)(i) ⎥⎦ IA(cid:68)u Si g(A) ⎢⎣ p(cid:68)(i) ⎥⎦
( i = Ni, Al, Al O )
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routine experiment… easy
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reference states / reaction enthalpies
measured IVTAN
reference state reaction (298K)
(kJmol-1) (kJmol-1)
363.5±2.8
{ Au(s,l) + C } Au(s,l) = Au(g) 367.0±0.9
367.0±1.3*
{ Ni(s) + Al O } Ni(s) = Ni(g) 428.3±2.6 428.0±8.0
2 3
Al(s) = Al(g) 341.0±2.2 330.0±3.0
4/3Al(s) + 1/3Al O (s) = Al O(g) 414.2±3.6 409.9±55
2 3 2
{ Al(l) + Al O } 2Al(s) + 3O(g) = Al O (s) ~ -3083.2 ±5
2 3 2 3
2Al(g) + O(g) = Al O(g) -1075.5±9.0 -1057.8±20.0
2
4Al(g) + Al O (s) = 3Al O(g) ~ ~
2 3 2
* 3rd law measurements
• pure-Al data is wrong,… use my second law data
• Au(s,l) ref. (cid:140) T and p(i) standards, good check of experiment
• measure 2 alloys in single experiment
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sensitivity of measurements?
Au(s,l) = Au(g)
xNi + yAl + zPt = γ-(NiAlPt)
T(K) T (K)
1450 1350 1250 1150 1750 1650 1550 1450
50
10-3 1
Go−Ho
40 FEF = T 298
T
) 30 L γ-(Ni)
T
u
A
I
(
n
Rl 20 l) i)
- A 10-4 N
F) a( a(
E
G 10
-
(
Δ
0
-10
10-5 0.1
6.5 7.0 7.5 8.0 8.5 9.0 5.6 6.0 6.4 6.8
104/T (K-1) 104/T (K-1) Ni-12Al-18Pt
[ ( ) ]
d Δ −FEF −RlnI T
Δ Ho (Au)= Au =362.2±1.7kJmol−1 Δ Gγ = RTlna(Al)=−124.4±0.8kJmol−1
sub 298 d1T mix Al
= 6.018 ± 0.029eV/atom = -2.10 ± 0.015eV/atom
Δ Ho (Au)=T[Δ(−FEF)−Rln p(Au)]=366.3±0.8kJmol−1 Δ Gγ = RTlna(Ni)=−4.5±0.9kJmol−1
sub 298 mix Ni
= 6.086 ± 0.013eV/atom = -0.08 ± 0.015eV/atom
R. C. Paule, J. Mandel: NBS Special Publication 260-19, 1970.
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a(Al) vs 1/T in Ni-24Al-XPt
T (K)
1750 1650 1550 1450
10-3
L
−1
Δ H(Al)= −203±10kJmol
mix
γ'
)
l
A 10-4
(
a
t
P
/
i
N

g
Ni-24Al-2Pt n
i
s
Ni-24Al-10Pt a
e
Ni-24Al-18Pt r
c
Nci-o2n4Aglr-2u5ePnt t melting, T ≈ 1640K e
d
10-5
5.6 6.0 6.4 6.8
4 -1
10 /T (K )
E. Copland, J. Phase Equil. Diff., 28(1) (2007) 38
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a(Ni) vs 1/T in Ni-24Al-XPt
T (K)
1750 1650 1550 1450 1350
1.0
γ'
L
)
l
A
(
a
Ni-24Al-2Pt
Ni-24Al-10Pt
Ni-24Al-18Pt
Ni-24Al-25Pt
0.1
5.6 6.0 6.4 6.8 7.2
4 -1
10 /T (K )
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hypo- / hyper-stoichiometric γ´
T (K)
1750 1650 1550 1450
10-3
L
γ'
)
l
A
(
a
10-4
Ni-24Al-10Pt
Ni-27Al-10Pt ~55 kJmol-1
Ni-24Al-18Pt
Ni-27Al-18Pt
~45 kJmol-1
-5
30
5.6 6.0 6.4 6.8
4 -1
10 /T (K )
10