role of zirconium on the oxidation resistance of … filerole of zirconium on the oxidation...

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


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


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


-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


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


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


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?


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


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


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.


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


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


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


Acknowledgments

Eric Dubois (Snecma) for providing access to the Setaramthermobalance.

The financial contribution of DGA (Délégation Générale pour l’Armement)

16

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

role of zirconium on the oxidation resistance of … filerole of zirconium on the oxidation...

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