Advanced Low Conductivity Thermal Barrier Coatings: · PDF file · 2013-04-10In this presentation, thermal barrier coating development ... Advanced Low Conductivity Thermal Barrier

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

Dongming Zhu and Robert A. Miller

NASA Glenn Research Center 21000 Brookpark Road, Cleveland, Ohio 44135

Thermal barrier coatings will be more aggressively designed to protect gas turbine

engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

https://ntrs.nasa.gov/search.jsp?R=20100042394 2018-05-15T00:39:04+00:00Z

National Aeronautics and Space Administration

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Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

Dongming Zhu and Robert A. Miller

Durability and Protective Coatings Branch, Structures and Materials DivisionNASA John H. Glenn Research Center

Cleveland, Ohio 44135, USA

35th International Conference On Metallurgical Coatings And Thin Films (ICMCTF 2008)San Diego, California, April 27-May 2, 2008

Contact: Dr. Dongming Zhu(216) 433-5422

[email protected]


www.nasa.gov

Acknowledgments

This work was supported by NASA Fundamental Aeronautics (FA) Program Supersonics and Subsonic Rotary Wing Projects.

Howmet CoatingsHoneywell EnginesUCSBDirect Vapor Technol.

GE AviationPratt and WhitneyRolls Royce-Liberty WorksSUNY/Mesoscibe Tech.

Collaborators


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Motivation— Thermal barrier coatings (TBCs) can significantly increase gas

temperatures, reduce cooling requirements, and improve engine fuel efficiency and reliability

(a) Current TBCs (b) Advanced TBCs

Ceramic coating

Ceramic coating

SubstrateSubstrateBond coat

Bond coat

Tgas

Tsurface

Tgas

Tsurface

TbackTback

Ceramic coating

Ceramic coating


Bond coat

Tgas

Tsurface

Tgas

Tsurface

TbackTback

Ceramic coating

Ceramic coating


Bond coat

Tgas

Tsurface

Tgas

Tsurface

TbackTback

Turbine

Combustor Vane Blade Ceramic nozzles

CMC combustor liner and vane

Turbine

Combustor Vane Blade Ceramic nozzles

CMC combustor liner and vaneCMC combustor liner and vaneCMC combustor liner and vane


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NASA Ceramic Coating Development Goals— Meet engine temperature and performance requirements

- improved engine efficiency - reduced emission- increase long-term durability

— Improve technology readiness— The programs require a step-increase in coating capability— Reliability critical

2400°F (1316°C)

3000°F+ (1650°C+)

Gen I

Temperature Capability (T/EBC) surface

Gen II – Current commercialGen III

Gen. IV

Increase in ∆T across T/EBC

Single Crystal Superalloy

Year

Ceramic Matrix Composite

Gen I

Temperature Capability (T/EBC) surface

Gen II – Current commercialGen III

Gen. IV

Increase in ∆T across T/EBC

Single Crystal Superalloy

Year

Ceramic Matrix Composite

2700°F (1482°C)

2000°F (1093°C)

Step increase in temperature capability3000°F SiC/SiC CMC coatings2700°F SiC/SiC CMC and Si3N4

coatings

2800ºF combustor TBCs

2500ºF Turbine TBCs


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Outline─ Simulated high-heat-flux testing approaches

• Laser high heat flux• Burner and laser high temperature erosion• High pressure burner and high heat-flux capability

─ Low conductivity thermal barrier coating developments• Low conductivity TBC design requirements • Performance of low k four-component TBC systems

Conductivity, and cyclic durability• High toughness Low k four- and six-component turbine airfoil

TBC development – erosion resistance• CMAS interaction testing

─ Future directions

─ Summary


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High Heat-Flux Test Approaches– High-heat-flux tests crucial for turbine TBC developments

• CO2 laser simulated turbine engine high-heat-flux rig• Atmospheric burner rig simulated heat flux testing• High pressure burner rig simulated engine heat flux and pressure environments

High pressure burner rig combustion flow seen from viewport

TC

Atmospheric burner rig

High power CO2 Laser high heat flux rig

Tsurface2400-2500°F

(1316-1371°C)Tinterface

1950°F(1066°C)

- ∆T ~450°F (250°C) across 5mil coating- Heat flux up to 400 W/cm2

Turbine blade TBC testing requirements

T

Dis

tanc

e fr

om s

urfa

ce

Heat flux

cooling hc=0.4 W/cm2-K max

TBC


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High Velocity Burner Erosion Rig and Laser high Heat Flux Erosion Test Rig for Turbine TBC Testing

Erosion jet

High precision particle feeder system

Specimens under testing

Mach 0.3-1.0 burner erosion rig Laser heat flux erosion rig


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ZrO2-(7-8) wt%Y2O3Thermal Barrier Coating Systems

Relatively low intrinsic thermal conductivity ~2.5 W/m-K High thermal expansion to better match superalloy substrates Good high temperature stability and mechanical properties Additional conductivity reduction by micro-porosity

100 µm

Ceramic coating

Bond coat

(a) Plasma-sprayed coating

25 µm

Ceramic coating

Bond coat

(b) EB-PVD coating


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0.0

0.5

1.0

1.5

2.0

2.5

3.0

Plasma-sprayed TBC EB-PVD TBC

Ther

mal

con

duct

ivity

, W/m

-K

Coating Type

Conductivity reduction by microcracks and microporosity

— Significant conductivity increase at high temperature due to sintering— Accelerated failure due to phase stability and reduced strain tolerance

Intrinsic ZrO2-Y2O3

conductivity

As received conductivity(EB-PVD)As received conductivity(Plasma Coating )

20-hr rise at 1316°C




Sintering and Conductivity Increase of ZrO2-(7-8) wt%Y2O3


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Sintering Kinetics of Plasma-Sprayed ZrO2-8wt%Y2O3Coatings

−−

−⋅=

−

−τt

RTkkkk

cc

cc exp168228exp2.1020inf

0

⋅=RT

41710exp5.572τ

Zhu & Miller, Surf. Coat. Technol., 1998; MRS Bulletin, 2000


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Sintering Cracks and Delaminations

— High heat flux surface sintering cracking and resulting coating delaminations

Tsurface=1280°CTinterface=1095°CThickness=130 µm

Zhu et al, Surf. Coat. Tech., 138 (2001), 1-8

surface vertical cracks

Delamination cracks

50 µm


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Sintering Cracks and Delaminations- continued

— Sintering strain corresponding to the thermal gradient across the coating (Tsurface=1280°C, Tinterface=1095°F)

0.00

0.50

1.00

1.50

2.00

0 50 100 150 200 250

0 hr46 hr200 hrmean strain

Surf

ace

open

ing

stra

in, %

Time, hours

strain (in%) = 0.40757 + 0.41 · t (in hr) 0.2

100 µm


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Low Conductivity and Sintering Resistant Thermal Barrier Coating Design Requirements

— Low conductivity (“1/2” of the baseline) retained at 2400°F— Improved sintering resistance and phase stability (up to 3000°F)— Excellent durability and mechanical properties

• Cyclic life• Toughness• Erosion/impact resistance• CMAS and corrosion resistance• Compatibility with the substrate/TGO

— Processing capability using existing infrastructure and alternative coating systems

— Other design considerations• Favorable optical properties• Potentially suitable for various metal and ceramic components • Affordable and safe


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Low Conductivity Thermal Barrier Coating Design Approaches

Efforts on modifying coating microstructures and porosity, composite TBCs, or alternative oxide compounds

Emphasize ZrO2- or HfO2-based alloy systems – defect cluster approach for toughness consideration

Advantages of defect cluster approach

• Advanced design approach: design of the clustering

• Better thermal stability: point defects are thermodynamically stable

• Improved sintering resistance: effective defect concentration reduced and activation energies increased by clustering

• Easy to fabricate: plasma-sprayed or EB-PVD processes


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Development of Advanced Defect Cluster Low Conductivity Thermal Barrier Coatings

— Multi-component oxide defect clustering approach (Zhu and Miller, US Patents No. 6,812,176, No.7,001,859, and No. 7,186,466)

— Defect clusters associated with dopant segregation— The nanometer sized clusters for reduced thermal conductivity, improved

stability, and mechanical properties

EELS elemental maps of EB-PVD ZrO2-(Y, Gd,Yb)2O3

Plasma-sprayed ZrO2-(Y, Nd,Yb)2O3

EB-PVD ZrO2-(Y, Nd,Yb)2O3

e.g.: ZrO2-Y2O3-Nd2O3(Gd2O3,Sm2O3)-Yb2O3(Sc2O3) systemsPrimary stabilizer

Oxide cluster dopants with distinctive ionic sizes

Zhu et al, Ceram. Eng. Sci. Proc., 2003


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Defect Clusters in a Plasma-Sprayed Y2O3, Nd2O3 and Yb2O3 Co-Doped ZrO2-Thermal Barrier Coating

— Yb, Nd rich regions consisting of small clusters with size of 5 to 20 nm

Energy (keV)

Cou

nts

20151050

1000

800

600

400

200

0

Cu

Cu

Cu

OAl

Mo

Mo

Zr

Zr

Y

Y

Yb

YbYb

Yb

YbNd

Nd

Nd

Nd

5 nm5 nm

Yb, Nd rich region clusters

Energy (keV)

Cou

nts

151050

1200

1000

800

600

400

200

0

Mo

Mo

Cu

Cu

Cu

Zr

Zr

Zr

ZrZr

Nd

NdNd

NdNd

Y

Y

Y

Y

ScSc

Yb

YbYb

Yb

Yb

O

Overall EDS

Yb rich region EDS

~40Å

(111)

~11.4Å

9.07Å


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Low Conductivity Defect Cluster Coatings Demonstrated Improved Thermal Stability

(a) Plasma-sprayed coatings

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Ther

mal

con

duct

ivity

, W/m

-K

Time, hours

ZrO2-4.55mol%Y

2O

3 (ZrO

2-8wt%Y

2O

3 )

ZrO2-13.5mol%(Y,Nd,Yb)

2O

3

rate increase: 2.65×10-6 W/m-K-s


1316°C

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15 20 25

ZrO2-4mol%Y

2O

3 (ZrO

2-7wt%Y

2O

3 )

ZrO2-4mol%Y2O

3 (ZrO

2-7wt%Y

2O

3 )

Low conductivity ZrO2-10mol%(Y,Gd,Yb)

2O

3 coating

Ther

mal

con

duct

ivity

, W/m

-K

Time, hours

rate increase: 2.2-3.8×10-6 W/m-K-s


1371°C

(b) EB-PVD coatings

— Thermal conductivity significantly reduced at high temperatures for the low conductivity TBCs


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Thermal Conductivity of Defect Cluster Thermal Barrier Coatings

(k0, k5 and k20 are the initial thermal conductivity, and the conductivity at 5 and20 hours, respectively)EB-PVD coatings

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25 30

k2 0

-YSZ-Nd-Yb

k20

-YSZ-Gd-Yb

k20

-YSZ-Sm-Yb

k20

-YSZ

k5-YSZ-Gd-Yb

k5-YSZ-Gd-Yb-Sc

k5-YSZ-Nd-Yb-Sc

k0-4.55YSZ

k5-4.55YSZ

The

rmal

con

duct

ivity

, W/m

-K

Total dopant concentration, mol%

YSZ coatings4.55YSZ k

0

4.55YSZ k20

cluster oxide coatings

4.55YSZ k5

t’ phase region Cubic phase region


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Thermal Conductivity of Defect Cluster Thermal Barrier Coatings

— Thermal conductivity benefit of oxide defect cluster thermal barrier coatings demonstrated

Plasma-sprayed coatings(k0, and k20 are the initial thermal conductivity, and the conductivity at 5 and20 hours, respectively)


0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2 4 6 8 10 12 14

8YSZ k0 (2500F)8YSZ k20 (2500F)8YSZ k0 (2600F)8YSZ k20 (2600F)Refractron k0 (~2500F)Refractron k20 (~2500F)Refractron k0 (~2700F)Refractron k20 (~2700F)Praxair k0 (2500F)Praxair k20 (2500F)NASA k0 (2500F)NASA k20 (2500F)

Ther

mal

con

duct

ivity

, W/m

-K


Plasma-sprayed coatings

AdvancedZrO2-based

coatings

k0k20k0k20k0k20k0k20


0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2 4 6 8 10 12 14


Ther

mal

con

duct

ivity

, W/m

-K



AdvancedZrO2-based

coatings

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2 4 6 8 10 12 14


Ther

mal

con

duct

ivity

, W/m

-K



0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2 4 6 8 10 12 14


Ther

mal

con

duct

ivity

, W/m

-K



AdvancedZrO2-based

coatings

k0k20k0k20k0k20k0k20


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Furnace Cyclic Behavior of ZrO2-(Y,Gd,Yb)2O3Thermal Barrier Coatings

― t’ low k TBCs had good cyclic durability― The cubic-phase low conductivity TBC durability needed improvements

Zhu and Miller, Ceram. Sci. Eng. Proc., 2002

EB-PVD

0

100

200

300

400

500

600

0 5 10 15 20 25 30 35

YSZ-Nd-YbYSZ-Gd-YbYSZ-Sm-YbYSZ

Cyc

les

to fa

ilure


YSZ


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Furnace Cyclic Behavior of ZrO2-(Y,Gd,Yb)2O3Thermal Barrier Coatings - Continued

― t’ low k TBCs had good cyclic durability― The cubic-phase low conductivity TBC durability initially improved by an

7YSZ or low k t’-phase interlayer

0

200

400

600

800

1000

4 5 6 7 8 9 10 11 12

Cubic phase low k TBCTetrogonal t' phase low k TBCs8YSZ

Cyc

les t

o fa

ilure


2075°F (1135°C)

Low-k t’-phase region

Low-k cubic phase region

With the interlayer

1135°C

Without interlayer

0

200

400

600

800

1000

4 5 6 7 8 9 10 11 12


Cyc

les t

o fa

ilure


2075°F (1135°C)



With the interlayer

1135°C

0

200

400

600

800

1000

4 5 6 7 8 9 10 11 12


Cyc

les t

o fa

ilure


2075°F (1135°C)



With the interlayer

0

200

400

600

800

1000

4 5 6 7 8 9 10 11 12


Cyc

les t

o fa

ilure


2075°F (1135°C)



With the interlayer

1135°C

Without interlayer

EB-PVD low k coatings


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Advanced Low Conductivity TBC Showed Excellent Cyclic Durability

― Coating validated for down-selected low conductivity coating systems

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500

Ther

mal

con

duct

ivity

, W/m

-K

Time, hours

Cycle number

Tsurface=2480°F (1360°C)Tinterface=2020°F(1104°C)

6 min heating, 2 min cooling cycles

Low conductivity EB-PVD turbine airfoil coating

0.0

0.5

1.0

1.5

0 50 100 150 200 250

Ther

mal

con

duct

ivity

, W/m

-K

Time, hours

Tsurface=3000°F(1650°C)Tinterface=1670°F(910°C)

3030, 3min heating & 1.5min cooling cycles completed

Low conductivity plasma-sprayed combustor coating

Laser heat flux tests

Burner rig tests


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Advanced Low Conductivity Combustor Thermal Barrier Coating Developments

― Low k TBC coated components demonstrated in simulated engine environments

― Low k TBC being incorporated in advanced engine development programs

Low conductivity TBC combustor liner demonstration in Combustor rig

Low conductivity TBC Propulsion 21 flame tube and deflector

demonstrations

Low conductivity TBC flame tube and combustor deflector demos in Advanced Subsonic Combustion Rig (ASCR)

Flame tube

Low conductivity TBC: combustor liner demonstration

Outer liner

Inner liner


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Erosion and Impact Resistant Turbine TBC Development

— Multi-component ZrO2 low k coatings showed promise in improving erosion and impact resistance

0

50

100

150

200

250

300

350

ErosionImpact

Ero

sion

and

impa

ct re

sist

ance

(spe

cific

ero

dent

wei

ght r

equi

red

to p

enet

rate

coa

ting)

, m

g/pe

r mil

coat

ing

thic

knes

s

Coating type

ZrO2-7wt%Y

2O

3Cubic-phase

multi-component coating

High toughness, tetragonal multi-component coating

EB-PVD coatings Erosion and impact resistance, measured as the erodent Al2O3 weight required to penetrate unit thickness coating

2200°F burner rig erosionZhu & Miller, NASA R&T, 2004


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Advanced Multi-Component Erosion Resistant Turbine Blade Thermal Barrier Coating Development

─ Rare earth (RE) and transition metal oxide defect clustering approach (US Patents No. 6,812,176, No.7,001,859, and 7,186,466; US patent application 11/510,574 ) specifically by additions of RE2O3 , TiO2 and Ta2O5

─ Significantly improved toughness, cyclic durability and erosion resistance while maintaining low thermal conductivity

─ Improved thermal stability due to reduced diffusion at high temperature

ZrO2-Y2O3- RE1 {e.g.,Gd2O3,Sm2O3}-RE2 {e.g.,Yb2O3,Sc2O3} – TT{TiO2+Ta2O5} systemsPrimary stabilizer

Oxide cluster dopants with distinctive ionic sizesToughening dopants


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Furnace Cyclic Test Lifetime and Thermal Conductivity of TiO2 Doped Thermal Barrier Coatings

─ Unpublished work 2003

0

100

200

300

400

500

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Cubic low k 433 FCT lifeCubic 433+10TiO

2 low k FCT life

Cubic low k 433 low k thermal conductivityCubic 433+10TiO

2 low k thermal conductivity

FCT

cycl

es to

failu

re, h

r

Ther

mal

con

duct

ivity

, W/m

-K

Cub

ic 4

-com

pone

nt

Cub

ic 5

-com

pone

nt (R

e 2O3+T

iO2)

Cub

ic 4

-com

pone

nt

Cub

ic 5

-com

pone

nt (R

e 2O3+T

iO2)

EB-PVD

0

100

200

300

400

500

600

0 5 10 15 20 25 30 35

YSZ-Nd-YbYSZ-Gd-YbYSZ-Sm-YbYSZ

Cyc

les

to fa

ilure


YSZ


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Furnace Cyclic Lifetime of Advanced Turbine Thermal Barrier Coatings

─ Furnace cyclic life can be optimized with RE2O3 and TT additions─ Stability and volatility with too high TT concentrations

0

100

200

300

400

500

2 4 6 8 10 12 14

Four-component low k7YSZ

Cyc

les t

o fa

ilure

, hr

Totoal RE2O

3 dopant concentration

2125°F (1163°C)

Six-componnet low k (with TT addtions)

TT concentration


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Cyclic Life of Four-Component Thermal Barrier Coatings

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

0.00069 0.00070 0.00071 0.00072 0.00073 0.00074 0.00075

Zr2.5Y0.75Gd0.75Yb (ln)Zr2.0Y1.5Gd1.5Yb (ln)Zr1.6Y1.2Gd1.2Yb (ln)Zr2.5Y0.75Gd0.75Yb (Ln)Zr2.0Y1.5Gd1.5Yb (Ln)Zr1.6Y1.2Gd1.2Yb (Ln)Zr2.5Y0.75Gd0.75Yb (2h) (Ln)Zr2.0Y1.5Gd1.5Yb (2h) (Ln)Zr1.6Y1.2Gd1.2Yb (2h) (Ln)7YSZ (ln)7YSZ (Ln)7YSZ (2h) (Ln)7YSZ7YSZ Laser heat flux7YSZ burner rig

ln (C

ycle

tim

e to

failu

re),

hour

s

1/T, 1/K

1436 1423 1408 1338

Temperature, K

─ Furnace and high heat flux cyclic life being optimized for long-term durability


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Thermal Conductivity of Selected Low k Thermal Barrier Coatings

0.0

0.5

1.0

1.5

2.0

2.5

4.5 5.0 5.5 6.0 6.5 7.0

ZrO2-8wt%Y

2O

3 k20

ZrO2-8wt%Y

2O

3 anti-sin tering k20

Refarctron k0Refactron k20Praxair k0Praxair k20NASA k0NASA k20PVD-ZrO

2-7wt%Y

2O

3 k20

PVD t' low k k20PVD cubic low k k20

Ther

mal

con

duct

ivity

, W/m

-K

1/T ·104, K -1

120013001500 14001600Tem perature, °C

Plasma-sprayed and EB-PVD coatings

AdvancedLow k TBCs


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Impact Resistance of Advanced Multi-component Low Conductivity Thermal Barrier Coatings

― Improved impact/erosion resistance observed for advanced low conductivity six-component coatings

0.0

0.5

1.0

1.5

2.0

2.5Zr

YG

dYb

t' -1

Zr

YG

dYb

t' -2

Zr

YG

dYb

t' -3

Zr

YG

dYb

t' -4

Zr

YG

dYb

Cub

ic m

ultil

ayer

Zr

YG

dYb

Cub

ic +

TT

Zr

O2-4

Y (b

asel

ine)

Advanced coatingsBaseline

Eros

ion

resi

stan

ce(E

roda

nt a

mou

nt re

quire

dpe

r mg

coat

ing

rem

oval

, g/m

g) 2200°F

>100%Improvements

650 micron Al2O3


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Erosion Resistance of Advanced Multi-component Low Conductivity Thermal Barrier Coatings

50 µm Al2O3

100% increase

0

5

10

15

20

25

30

ZrY

GdY

b t'

ZrY

GdY

b t'+

TT

ZrY

GdY

b C

ubic

+TT

ZrY

GdY

b C

ubic

ZrO

2-4Y

(bas

elin

e)

Advanced coatingsBaseline

Eros

ion

resi

stan

ce(E

roda

nt a

mou

nt re

quire

dpe

r mil

coat

ing

rem

oval

, g/m

il) 2175°F

─ The original cubic low k coating showed significant increase in erosion resistance due to the incorporation of TiO2 and Ta2O5


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Tetragonality of Multi-Component ZrO2 being Evaluated and Correlated to Coating Performance

Area detector x-ray diffractometer used for EB-PVD coatings

1 7 F 1 A 5 p o w d e r - In s tru m e n t C o m p a r is o n

A r e a D e te c to r P V DA r e a D e te c to r P o w d e r

Sqr

t (C

ps)

1

1 0

1 00

1 00 0

2 00

3 00

4 00

5 00

6 00

2 00 0

2 - T h e ta - S c a le7 2 . 5 73 7 4 7 5

─ Multi-component TiO2/Ta2O5 and rare earth dopants increase the tetragonality (c/a ratio)

─ Current efforts in optimizing the dopant composition ranges

1.000

1.010

1.020

1.030

1.040

1.050

2 4 6 8 10 12

7YSZZrO

2-MultiRE doped

ZrO2-RETiTa doped

c/a

ratio

RE dopant concentration

Higher TT dopant conc.

lower TT dopant conc.


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Impact Failure of Advanced Multi-Component Low Conductivity Thermal Barrier Coatings

30 um30 um

Surface sintering and impact densification zone

SEM micrographs of advanced thermal barrier coating after impact/erosion damage

Backscattered electron imageSecondary electron image

― Surface sintering and impact densification zones observed, with subsequent spallation under the erodent further impacts

― Toughened structures observed


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Impact Failure of Advanced Multi-Component Low Conductivity Thermal Barrier Coatings

Coating 1Coating 2

Eros

ion

rate

Time

Near failure

Initial rate

desified region

steady-state

fast failure region

30 um

─ Effect of erosion parameters will be modeled and validated


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High Heat Flux Testing of Turbine EB-PVD Thermal Barrier Coatings to Study CMAS Effect

─ Specimens typically tested at Tsurface ~2400ºF, Tinterface 2000°F─ Heat flux up to 250-300 W/cm2, cooling heat transfer coefficient up to hc

0.32 W/cm2-K─ Accelerated failure observed with CMAS interactions ─ Advanced multi-component coatings completed 50 hr testing

Specimen under the rig test

(a) Upon initial heating

(b) After testing

Combustor TBC

Baseline coating

Turbine TBCs

Advanced coatings50 hrs


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Future Directions for Low Conductivity TBC Development

— Emphasize high heat flux durability and erosion resistance

- Optimize high toughness erosion resistant turbine coatings

- Improve turbine airfoil TBCs with up to 3x erosion resistance

- Emphasize creep, fatigue, erosion, and CMAS interactions

- Develop multilayered damping and erosion coatings

- Develop turbine blade TBC life prediction model


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High temperature capability thermal and radiation barrier

Energy dissipation and chemical barrier interlayer

Environmental barrier

Advanced bond coat

Ceramic matrix composite (CMC)

Tsurface >1482°C (2700°F)

Tcoating/CMC interface <1316°C (2400°F)




Advanced bond coat





Advanced bond coat






127 µm(0.005”)

CMC Turbine Blade coatings

Future Directions for Low Conductivity TBC Development

CMC combustor liner and vane

— Emphasize thin ceramic matrix composite turbine coating processing- Advanced processing for integrated TEBCs

- Ceramic nanocomposite and nanotube-based TEBCs for improved durability and optical properties

- Embedded sensors

- Life prediction methodology and design tool development


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Summary

• Four-component low k TBC systems developed for low k combustor applications

• Advanced turbine airfoil TBCs being developed with combined low conductivity and high toughness

• Improved erosion/impact resistance observed for the multi-component coating t’ and t’/cubic nano-composite systems

• Coatings being optimized for cyclic life, thermal conductivity and erosion/impact and CMAS resistance

• High heat flux durability, multifunctional coatings and lifingmodels being emphasized in the current research programs

Documents

Advanced Low Conductivity Thermal Barrier Coatings: · PDF file · 2013-04-10In this presentation, thermal barrier coating development ... Advanced Low Conductivity Thermal Barrier