1
ROLE OF ZIRCONIUM ON THE OXIDATION RESISTANCE OF NICKEL ALUMINIDE COATINGS
S. Hamadi, M.-P. Bacos, M. Poulain, ONERA, FranceA. Seyeux, V. Maurice, P. Marcus, Ecole Nationale Supérieure de Chimie de
Paris, France
2Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
Background
Engine schematic diagram
Aeronautical turbine bladesare located at the combustion chamber exit. They are thenexposed to the hot combustion gases. The temperature canreach about 1600°C.
Rafale military planeAeronautical turbine blades
Turbine blade
High pressure turbine
Nozzle
High pressure turbine shaft
High pressure compressor
Low pressure compressor
Low pressure turbine shaft
Combustion chamber
Low pressure turbine
3Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
BackgroundThermal barrier systems
Thermal Barrier systemTurbine bladecross section 1150 - 1200 °C
Ni-basedsuperalloy
β-NiAl(X) coating
YSZ(ZrO2-Y2O3)
alumina
100 µm
600 - 700°CInternal cooling
Thermal barrier layer
(mechanical properties)
Thermal barrier
Internal cooling
1100°CKey point:adhesion of thermally grownalumina on top of the NiAl coating
4Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
BackgroundNiAl(X) coatings
Influence of adding elements on the oxide adhesion
3 types of NiAl coating• unmodified NiAl• Pt-modified NiAl: great improvement of alumina adhesion, system in
production, high processing costs• Zr-doped NiAl: Zr as a reactive element is said to improve alumina adhesion
on NiAl and NiCrAl bulk materials *NiAl(Zr) has to be investigated as a coating. One-step elaborating process.
Studied systemNi-based superalloy: AM1 (Ni, Cr, Co, Mo, W, Al, Ti, Ta)oxidation protective coating: Zr-doped NiAlNo thermal insulating topcoat
What is the role of Zr on the oxidation resistance of the NiAl coating?
* Smialek, 1987 ; Pint et al., 1996
5Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
-25
-20
-15
-10
-5
0
0 1000 2000 3000 4000 5000
Cyclic oxidation testsAM1/NiAl(Zr) efficiency
AM1/NiAl(Zr): better oxidation resistance than AM1/NiAl. WHY ?
as efficient as the industrial system
Mas
s va
riatio
n (m
g.cm
-2)
Nb of 1h-cycles at 1100°C lab air
AM1/NiAl(Zr)AM1/NiAl
Oxide growth
Oxide spallation
Failure criterion2500 cycles 4100 cycles
6Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
AM1/NiAl(Zr) characterizationProcess
at. % of ZrDeposition process*
µm
Coating
Interdiffusion Zone
GDMS depth profile
* * * * * * *
H2, 1100°C
Cr-Al
ZrOCl2,8H2O
ZrCl4 AlCl
NiAl(Zr) coating:β-NiAl phase (XRD)
Al: 36 at. % (EPMA)
Zr: 300 at. ppm (GDMS)~ 20 µm from the surface
Vapor Phase co-depositionof Al and Zr on AM1Ni-based superalloy
* M.-P. Bacos, P. Josso, and S. Navéos, Patent FR2853329 B1 (2006).
EPMA: Electron Probe Micro AnalysisGDMS: Glow Discharge Mass Spectrometry
7Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
AM1/NiAl(Zr) characterization
as aluminized
0 20 40
Zr
µm
GDMS depth profile
NiAl(Zr)
AM1
Zr
Zr distribution in oxidising conditions
20 µm
0
0.4
0.2at. %
AM1
Zr
27Al+
58Ni+
90Zr+
ToF-SIMS depth profile
oxidised 50 1h-cycles 1100°C
1 µm
Inte
nsity
(cou
nts) 105
103
102
104
101
0
106
Sputtering time (min)0 10020 806040
oxide
NiAl(Zr)
27Al+
58Ni+
90Zr+
27Al-
58Ni-
90Zr-
NiAl(Zr)
AM1
ToF-SIMS depth profile
oxidised 10 min 950°C
Surfaceanalysis
0.1 µm
Zr
ZrIn
tens
ity(c
ount
s)
105
103
102
104
101
Sputtering time (min)0 6030
27Al-
58Ni-90Zr-
oxide
8Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
AM1/NiAl(Zr) characterization
Zr diffuses quickly trough the coating towards the metal/oxide interface.
After longer oxidation, Zr is present in all the layers of the sample.
Comparison between the AM1/NiAl and the AM1/NiAl(Zr) systems:
1. β-NiAl ageing
2. oxide growth
How does Zr improve the oxidation resistance of NiAl?
9Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
1. β-NiAl ageing
NiAl: The whole coating isγ phase as soon as 500 oxidation cycles
1h-cyclic oxidation tests
NiAl(Zr): β-phase is still presentafter 500 oxidation cyclesthe coating is γ/γ’ after 1000 and 1500 oxidation cycles
Zr delays the coating ageing
β-NiAl fraction (%)
β-NiAl +γ’-Ni3Al
β-NiAl +γ’-Ni3Al
γ’-Ni3Al+ γ-Ni
γ-Ni
AM1/NiAlAM1/NiAl(Zr)
Nb 1h-cycle 1100°C0
100 500 1500
γ-Ni
100
50
0
β-NiAl
γ’-Ni3Al
γ-NiAM1 Ni-basedsuperalloy
Ni Al
Thermally grown Al2O3
100% Al 100% Ni
1100°C
10Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
2. Oxide growthIsothermal 1100°C oxidation tests
96 h 1100°C, synthetic air, followed by TGA
AM1/NiAl
AM1/NiAl(Zr)
Transient regime:fast oxide growth first few hours
hStationary regime:slow oxide growth
Mas
s va
riatio
n (m
g.cm
-2)
∆t1, kp1 ∆t2, kp2
time
∆m/S
The parabolat = A + B ∆m/S + 1/kpkp (∆m/S)²is used to fitthe isothermal oxidation curves on selected intervals
Zr lowers the global mass gain
Reduces the oxide thickness
11Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
2. Oxide growthGrowth kinetics t = A + B ∆m/S + 1/kpkp (∆m/S)²
metastable θ-Al2O3
h
stable α-Al2O3
AM1/NiAl
Transient regime Stationary regime
1,E-09
1,E-08
1,E-07
1,E-06
1,E-05
1,E-04
1,E-03
0 2 4
kp (m
g².c
m-4
.s-1
)
96 h5
O
Alθ-Al2O3
NiAl
O
Alα-Al2O3
NiAlAM1/NiAl(Zr)
Transient regime
Transientregime
• Zr has no major effect on θ and α growth kinetics.
• Zr reduces the transient regime duration.
• When exposed to oxidation at 1100°C, as Zr reduces the period during wich θ-alumina grows, it reduces the formation of interfacial cavities.
12Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
Long-term cyclic oxidations
AM1/NiAl
AM1/NiAl(Zr)
50 cycles 1500 cycles
1h-cyclic oxidation tests
500 cycles
cavity
spalled areas
oxide
metal
oxide
metal
10 µm
10 µm
Oxidised surfaces
20 µm
20 µm
AM1/NiAl(Zr)
• The alumina is more adhesive
• Oxide spallation is delayed, as well as spallations/reoxidations that leadto metal consumption
13Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
AM1/NiAl(Zr)AM1/NiAl
coatingZr is located at the
superalloy/coating interfaceAs-deposited
superalloy
θ-Al2O3 α-Al2O3 Zr migrates through the coating and favours α-Al2O3
Short-time oxidationcavity
oxide
spallation
Zr delays the oxidespallationLong-term oxidation
coating
superalloy
14Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
Conclusions
• Zr reduces the transient regime of oxidation, favouringalpha alumina nucleation
• Zr reduces cavities and delays the oxide spallation
Zr increases the system lifetime
NiAl(Zr) promising protective coating, is being investigatedas a bond coat in TBC systems
15Role of zirconium on the oxidation resistance of nickel aluminide coatingsSarah HAMADI (ONERA, ENSCP) – Euromat 2009
Acknowledgments
Eric Dubois (Snecma) for providing access to the Setaramthermobalance.
The financial contribution of DGA (Délégation Générale pour l’Armement)