thermal and environmental barrier coatings for advanced … · 2016. 10. 26. · thermal and...

Dongming ZhuU.S. Army Research Laboratory, Glenn Research Center, Cleveland, Ohio

Robert A. MillerGlenn Research Center, Cleveland, Ohio

Thermal and Environmental Barrier Coatingsfor Advanced Turbine Engine Applications

NASA/TM—2005-213437

March 2005

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Dongming ZhuU.S. Army Research Laboratory, Glenn Research Center, Cleveland, Ohio

Robert A. MillerGlenn Research Center, Cleveland, Ohio

Thermal and Environmental Barrier Coatingsfor Advanced Turbine Engine Applications

NASA/TM—2005-213437

March 2005

National Aeronautics andSpace Administration

Glenn Research Center

Prepared for the2004 Fall Meetingsponsored by the Materials Research SocietyBoston, Massacusetts, November 29–December 03, 2004

Available from

NASA Center for Aerospace Information7121 Standard DriveHanover, MD 21076

National Technical Information Service5285 Port Royal RoadSpringfield, VA 22100

Available electronically at http://gltrs.grc.nasa.gov

Thermal and Environmental Barrier Coatings for Advanced Turbine Engine Applications

Dongming Zhu

U.S. Army Research Laboratory Glenn Research Center Cleveland, Ohio 44135

Robert A. Miller

National Aeronautics and Space Administration Glenn Research Center Cleveland, Ohio 44135

Abstract

Ceramic thermal and environmental barrier coatings (T/EBCs) will play a crucial role in advanced gas turbine engine systems because of their ability to significantly increase engine operating temperatures and reduce cooling requirements, thus help achieve engine low emission and high efficiency goals. Under the NASA Ultra-Efficient Engine Technology (UEET) program, advanced T/EBCs are being developed for the low emission SiC/SiC ceramic matrix composite (CMC) combustor applications by extending the CMC liner and vane temperature capability to 1650 °C (3000 °F) in oxidizing and water vapor containing combustion environments. Advanced low conductivity thermal barrier coatings (TBCs) are also being developed for metallic turbine airfoil and combustor applications, providing the component temperature capability up to 1650 °C (3000 °F). The advanced T/EBC system is required to have increased phase stability, low lattice and radiation thermal conductivity, and improved sintering, erosion and thermal stress resistance, and water vapor stability under the engine high-heat-flux and thermal cycling conditions. Advanced high heat-flux testing approaches have been established for the coating developments. The simulated combustion water-vapor environment is also being incorporated into the heat-flux test capabilities for evaluating T/EBC performance at very high temperatures under thermal cycling conditions.

In this paper, ceramic coating development considerations and requirements for both the ceramic and metallic components will be described for engine high temperature and high-heat-flux applications. The performance and durability of several ZrO2 or HfO2/mullite and mullite/BSAS model coating systems were investigated. The underlying coating failure mechanisms and life prediction approaches will be discussed based on the simulated engine tests and fracture mechanics modeling results. Further coating performance and life improvements will be expected by utilizing advanced coating architecture design, composition optimization, in conjunction with more sophisticated modeling and design tools.

NASA/TM—2005-213437 1



This work was supported by NASA Ultra-Efficient Engine Technology (UEET) Program

2004 MRS Fall MeetingBoston, MA

November 30, 2004

Dongming Zhu and Robert A. Miller

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

Cleveland, Ohio 44135, USA

NA

SA/T

M—

2005-2134373

Motivation

— Advanced thermal and environmental barrier coatings (T/EBCs) cansignificantly increase gas temperatures, reduce cooling requirements, and improve engine fuel efficiency and reliability

Tsurface

Tsurface

Ceramic coating

Bond coat

Metal substrate

TbackCeramic coating

Bond coat

Metal substrate

Tgas

Tgas

Tback

Tsurface

Tsurface

Ceramic coating

Bond coat

Metal substrate

Ceramic coating

Bond coat

Metal substrate

TbackCeramic coating

Bond coat

Metal substrate

Ceramic coating

Bond coat

Metal substrate

Tgas

Tgas

Tback

(a) Current T/EBCs (b) Advanced T/EBCs

Combustor Vane Turbine blade

Turbine

NA

SA/T

M—

2005-2134374

Revolutionary Ceramic Coatings Greatly Impact Gas Turbine Engine Technology

2400 °F

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

Si3N4 and coating systems

— Ceramic coatings are critical to future engine efficiency, power density and compactness goals

NASA UEET Goals• 70% NOx reduction• 8-15% increase in efficiency• 8-15% reduction in CO2

Coating Development Issues• Low thermal conductivity • High temperature stability• Erosion and radiation resistance

2700 °F

NA

SA/T

M—

2005-2134375

OBJECTIVES

• High-heat-flux and simulated engine test capabilities for advanced barrier coating developments– In-situ conductivity measurements and coating degradation

evaluation– Simulated engine testing– Sintering, strength and fracture behavior

• Low conductivity thermal barrier coatings

• The 3000 °F (1650 °C) thermal and environmental barrier coatings for SiC/SiC CMC and metallic combustors/vanes

• Advanced Si3N4 coating systems

NA

SA/T

M—

2005-2134376

NASA Steady-State Laser Heat-Flux Approach for Ceramic Coating Thermal Conductivity Measurements

▬ A uniform laser (wavelength 10.6 µm) power distribution achieved using integrating lens combined with lens/specimen rotation

▬ The ceramic surface and substrate temperatures measured by 8 micron and two-color pyrometers and/or by an embedded miniature thermocouple

▬ Thermal conductivity measured at 5 second intervals in real time

camera

pyrometer

cooling airthermocouple

specimen

3. 0 KW CO 2 High Power Laser

ceramic coatingbond coat

CMSX4 substrate

laser beam/ integrating lens

slip ring

300 RPM aluminum laser aperture plate

platinum flat coils

aluminum back plate

air gap

cooling air tube

TBC coated back aluminum

plate edge

miniature thermocouple

Ni-base superalloy or CMC substrate

reflectometer

NA

SA/T

M—

2005-2134377

Laser Heat Flux Testing in Water Vapor Environments for Si-Based Ceramics/Coatings

– Laser heat flux steam rig- Precise control of heat flux and temperatures of test specimen- Automated control of chamber temperature and steam environments- High temperature and high heat flux testing capabilities- Innovative “micro-steam environment” concept allows high vapor pressure, velocity and temperature as required- Real time specimen health monitoring capability

- Steam injected at up to 5m/sec- Testing temperature >1700 °C

Two-color and 7.9 µm pyrometers for

Tsubstrate-back

7.9 µm pyrometer for Tceramic-surface

radiatedqreflectedq

Optional miniature thermocouple for additional

heat flux calibrationthruq

thruq


substrate

bondsubstrate

measuredceramic

TTTT

∆−∆−∆=∆

∆Ttc

Two-color and 7.9 µm pyrometers for

Tsubstrate-back

7.9 µm pyrometer for Tceramic-surface

radiatedqreflectedq

Optional miniature thermocouple for additional

heat flux calibrationthruq

thruq


substrate

bondsubstrate

measuredceramic

TTTT

∆−∆−∆=∆

∆Ttc

Surface flow

Specimen under testing

Steam jets

Specimen holder and water vapor jets

Laser beam delivery and optic system

Infrared pyrometer

Laser heat flux water vapor test rigSpecimen under testing

Steam jetsSteam jets

Specimen holder and water vapor jets

Laser beam delivery and optic system

Infrared pyrometer

Laser heat flux water vapor test rig

NA

SA/T

M—

2005-2134378

High Pressure Burner Rig (HPBR) for Ceramic Coatings Testing

- Realistic combustion environments for specimen and component testing

• Burns jet fuel and air• Tgas: up to 1650 °C (3000 °F)• 4-12 atmospheres• 10-30 m/s (6” ID)• TC and optical temp.

measurement • Variable geometry

Test Section

Rail System

Combustor

1” button TEBC coating specimen holder for the burner rig testing

NA

SA/T

M—

2005-2134379

Thermal Conductivity of Current Thermal Barrier Coating Systems

Current thermal barrier coatings consist of ZrO2-8wt%Y2O3— 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 is achieved by incorporating micro-porosity

100 µm

Ceramic coating

Bond coat

25 µm

Ceramic coating

Bond coat

(b) EB-PVD coating(a) Plasma-sprayed coating

NA

SA/T

M—

2005-21343710

Coating Thermal Conductivity Reductions by Porosity are limited in Practical Applications

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

— The conductivity reduction achieved by microcracks and micro-porosity can not persist under high temperatures due to coating sintering

— The coating mechanical properties also affected by too high porosity

Intrinsic ZrO2-Y2O3conductivity

As received Conductivity k0(EB-PVD)As received Conductivity k0(Plasma Coating )

20-hr rise at 1316 °C

20-hr rise at 1316 °Ck20

k20

k0

k0

NA

SA/T

M—

2005-21343711

ZrO2-8wt%Y2O3/Mullite+BSAS/Si System under High Temperature Steady-State Laser Heat-Flux Testing

— ZrO2-8wt%Y2O3/mullite+BSAS TEBC system on SiC/SiC CMC tested at Tsurface1482 °C (2700 °F) and Tinterface 1300 °C (2350 °F)

— Conductivity initially increased due to sintering— Conductivity later decreased due to delamination resulting from the large

sintering shrinkage— Coating delaminates at temperature due to sintering/creep

TsurfaceTinterface=1250°C

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20

Measured thermal conductivityPredicted thermal conductivityT

herm

al c

ondu

ctiv

ity, W

/m-K

Time, hours

Conductivity reduction due to sintering cracking induced delamination cracking

500 mm

Sintering cracksAfter 20h testing

ZrO2-Y2O3Mullite+BSASSi =1482 °C

NA

SA/T

M—

2005-21343712

Sintering Behavior of the Plasma-Sprayed ZrO2-8wt%Y2O3 Coatings

— Sintering shrinkage as a function of time and temperature determined using dilatometer

― Sintering can induce surface cracking and delamination

ZrO2-8wt%Y2O3/Mullite+BSAS/Si System

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0

50

100

150

200

0 5 10 15 20

Shrik

age

stra

ins,

%

Ener

gy re

leas

e ra

te, J

/m2

Time, hours

GC

ETBC

~60GPa

thruC

G1500

mindelaC

G1500

thruC

G1400

mindelaC

G1400

NA

SA/T

M—

2005-21343713

Thermal Conductivity Increase Kinetics of Plasma-Sprayed ZrO2-8wt%Y2O3 Coatings due to Sintering

— The conductivity reduction by microcracks and micro-porosity can not persist under high temperatures due to coating sintering

— The coating durability can be affected by sintering

⎭⎬⎫

⎩⎨⎧

⎥⎦⎤

⎢⎣⎡−−⎟

⎠⎞

⎜⎝⎛−⋅=

−−

τt

RTkkkk

cc

cc exp168228exp2.1020inf0

⎟⎠⎞

⎜⎝⎛⋅=

RT41710exp5.572τ

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

15000 20000 25000 30000 35000

lnk at 990°Clnk at 1100°Clnk at 1320°C

lnk,

W/m

K

L-M=Tave·[lnt+10]

lnk= -0.560 + 2.9326·10-5 L-M

Thermal conductivity ZrO2-8wt%Y2O3 as a function of time and temperature at up to 1320 °C

NA

SA/T

M—

2005-21343714

Flexure Strength and Toughness Increases Kinetics as a Function of Annealing/Sintering Time

— Initially fast sintering induced strength and fracture toughness increases also observed for plasma-sprayed ZrO2-8wt%Y2O3 coatings

ANNEALING TIME, t [h]

0 100 200 300 400 500 600

FLE

XU

RE

ST

RE

NG

TH

, σf [

MPa

]

0

20

40

60

80

100

120

140

Flexure testing

ANNEALING TIME, t [h]

0 100 200 300 400 500 600FR

AC

TU

RE

TO

UG

HN

ESS

[MPa

m1/

2 ]

0.0

0.5

1.0

1.5

2.0

2.5

3.0

KIc

KIIc

S.D

Mode I KIc

B A

BA S

Mode II KIIc

NA

SA/T

M—

2005-21343715

Development of Advanced Defect Cluster Low Conductivity Thermal Barrier Coatings

— Multi-component oxide defect clustering approach used for the advancedcoating development – US Patent No. 6,812,176

— Defect clusters associated with the dopant segregation identified from moiré fringe patterns and electron energy loss spectroscopy (EELS) under high resolution TEM

— The 5 to 100 nm size defect clusters designed for the significantly reduced thermal conductivity and improved stability

EELS elemental maps of EB-PVD ZrO2-14mol%(Y, Gd,Yb)2O3

Plasma-sprayed ZrO2-13.5mol%(Y, Nd,Yb)2O3

EB-PVD ZrO2-12mol%(Y, Nd,Yb)2O3

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

Oxide cluster dopants with distinctive ionic sizes

NA

SA/T

M—

2005-21343716

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

Low Conductivity Oxide Defect Cluster Coatings Demonstrated Improved High Temperature Stability

Plasma-sprayed coatings

— Thermal conductivity rate-of-increase significantly reduced at high temperatures for the low conductivity defect cluster thermal barrier coatings

— Phase stability also improved

NA

SA/T

M—

2005-21343717

Low Conductivity Oxide Defect Cluster Coatings Demonstrated Improved High Temperature Stability

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

EB-PVD coatings

— Thermal conductivity rate-of-increase significantly reduced at high temperatures for the low conductivity defect cluster thermal barrier coatings

— Phase stability also improved

NA

SA/T

M—

2005-21343718

Thermal Conductivity of Oxides Cluster Thermal Barrier Coatings Tested at Higher Temperatures

― Both cubic phase low k coatings and t’ tetragonal plasma-sprayed coatings showed significantly lower thermal conductivity as compared to baseline ZrO2-8wt%Y2O3 under higher temperatures

t’ phase region Cubic phase region

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

Total dopant concentration, mol%


AdvancedZrO2-based

coatings

k0k20k0k20k0k20k0k20

t’ phase region Cubic phase region

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

NA

SA/T

M—

2005-21343719

Furnace Cyclic Behavior of Plasma-Sprayed ZrO2-(Y,Gd,Yb)2O3 Thermal Barrier Coatings

― The cubic-phase ZrO2-based low conductivity TBC durability can be further significantly improved by an 8YSZ or low k tetragonal t’-phase interlayer

― The tetragonal t’-phase low conductivity TBCs achieved at least the baseline 8YSZ life

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

NA

SA/T

M—

2005-21343720

Effects of Defect Cluster Dopant Ratio and Bond Coat Optimization on Coating Conductivity and Furnace Cyclic Life

― Optimized dopant ratio lowered coating conductivity and improved furnace cyclic life

― Bond coat and interface processing optimization can also improvedurability

0.0

0.5

1.0

1.5

0

1

2

3

k0-2500F-low k coatingsk20-2500F-low k coatingsk0-2200F-low k coatingsk20-2200F-low k coatings

Normalized cyclic life-low k coatings

Nor

mal

ized

ther

mal

con

duct

ivity

, W/m

-K(to

the

low

ratio

dop

ant c

oatin

g)

Nor

mal

ized

cyc

lic li

fe

(to th

e lo

w ra

tio d

opan

t coa

ting)

Cluster dopants/ Total dopants in mol%/mol%

Howmet processed NASA coating tested at 1371°C

(2500°F)&1204°F (2200°F)

Howmet processed NASA coating furnace cyclic tested

at 1165 °C (2125 °F)Bond coat &

interface processing optimization

NA

SA/T

M—

2005-21343721

2 µm

High toughness t’ phase such as in 8YSZ

Larger grains

Fracture surfaces

Larger grainsLarger grains

Fracture surfaces

Fast grain growth and low toughness ZrO2-10mol%Y2O3

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25 30 35

C luster oxide coatingYSZ coating

Obs

erve

d gr

ain

grow

th, µ

m

To tal dopan t concentration, m ol%

1165 °C

10.0 um10.0 um10.0 um10.0 um10.0 um

ZrO2-13.5mol%(Y,Gd,Yb)2O3Coating after 430, 1 hr

cycles at 1165 °C

Low Diffusion and High Toughness Coatings Showed Better Cyclic Life

NA

SA/T

M—

2005-21343722

― The low conductivity combustor and turbine airfoil thermal barrier coatings successfully tested under laboratory simulated engine thermal gradient cyclic conditions

― The low conductivity combustor and turbine airfoil thermal barrier coatings successfully tested under laboratory simulated engine thermal gradient cyclic conditions

Advanced Low Conductivity TBC Showed Excellent Long-Term High Temperature Cyclic Durability

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 cycles0.0

0.5

1.0

1.5

2.0

2.5

0 20 40 60 80 100 120 140

Ther

mal

con

duct

ivity

, W/m

-K

Time, hours

spallation

Low k 256:Tsurface 2800°F/Tinterface 2030°F200, 30 min cyclic after 20hr steady-state sintering test

7YSZ: Tsurface 2700°F/Tinterface 2030°F30 min cyclic after 20 hr steady-state sintering test

Low conductivity EB-PVD turbine airfoil coating

NA

SA/T

M—

2005-21343723

Development of Advanced Erosion Resistant Thermal Barrier Coatings

― Advanced high toughness, multi-component erosion resistant low conductivity thermal barrier coatings also under development

0

50

100

150

200

250

300

350ErosionImpact

Eros

ion

and

impa

ct re

sist

ance

(spe

cific

ero

dent

wei

ght r

equi

red

to p

enet

rate

coa

ting)

, m

g/m

il co

atin

g th

ickn

ess

Coating type

ZrO2-7wt%Y

2O

3Cubic-phase

multi-component coating

High toughness, tetragonalphase multi-component coating

EB-PVD coatings

Baseline coating Low conductivity coating

(a) Burner rig erosion and impact test results at 2200 °F

Baseline coating Low conductivity coating

(b) Room temperature erosion testing results for 2400 °F thermal

gradient tested specimens

0.0

0.5

1.0

1.5

2.0

2.5

3.0Erosion & Impact

Eros

ion

and

impa

ct re

sist

ance

(spe

cific

ero

dent

requ

ired

per c

oatin

g w

eigh

t los

s),

g/m

g

Coating type

ZrO2-8wt%Y

2O

3

Cubic-phasemulti-component coating

High toughness, tetragonal phasemulti-component coating


NA

SA/T

M—

2005-21343724

Advanced 3000 °F (1649 °C) Coatings

High temperature capability thermal and radiation barrierEnergy dissipation and chemical barrier interlayer

Secondary radiation barrier, thermal control with chemical barrier interlayer

Environmental barrierCeramic matrix composite (CMC)

— High temperature stability— Low thermal conductivity— Excellent thermal stress resistance— Enhanced radiative flux resistance and radiation cooling— Improved environmental protection— Designed functional capability

NA

SA/T

M—

2005-21343725

Advanced 3000 °F (1649 °C) Coatings Development for SiC/SiC Combustor Liner and Vane Applications

— The multicomponent hafnia(zirconia) coating/modified mullite systems demonstrated excellent cyclic durability and radiation resistance at 1650 °C (3000 °F)

— Advanced high temperature ceramic bond coats also developed

Modified mullite nano-composite interlayer coating

HfO2-Y2O3 coatings

Multi-component HfO2coating system

Steady-State 30 min cyclic

Tsurface=1650°C, Tinterface=1316°C0.5

1.0

1.5

2.0

0 20 40 60 80 100

Nor

mal

ized

ther

mal

con

duct

ivity

k/k

0

Time, hours

Sintering and cyclic durability evaluations

15YSHf

5YSHf

15(YGdYb)Hf

3100°F coatings3100°F coatings

NA

SA/T

M—

2005-21343726

Advanced Environmental Barrier Coatings for Si3N4 Applications

– Multi-layered, rare earth and silicon doped HfO2/mullite 2700 °F environmental barrier coating systems developed:– Advanced low expansion doped HfO2 used for high stability top layer– Modified mullite as the interlayer and environmental barrier– Doped HfO2 or mullite 2700 °F+ capable bond coats (eliminating Si bond

coat)– High Temperature plasma-spray technique used for coating processing

Multi-layer coating systems for 2700 °F Si3N4 components

Advanced doped HfO2

Doped HfO2/mullite bond coat

Si3N4

Doped mullite compositeModified mullite

environmental barrier

100 µ m100 µ m

A 2700 °F capable coating system for Si3N4

Plasma-spray processing of Environmental barrier coating

NA

SA/T

M—

2005-21343727

Coating Radiation Performance Evaluation and Radiation Barrier Coatings Development

— Radiation conductivity evaluated using the laser heat flux approach— Significant conductivity increase due to increased radiation at high

temperatures especially under thermal gradients

(b) Combined internal & external radiation

Ceramic coating

Laser heat flux Laser heat flux Laser heat flux

(a) Internal radiation

High emissivity layer

Ceramic coating Ceramic coating

(c) External radiation

Radiation emitter

(b) Combined internal & external radiation

Ceramic coating

Laser heat flux Laser heat flux Laser heat flux

(a) Internal radiation

High emissivity layer

Ceramic coating Ceramic coating

(c) External radiation

Radiation emitter

0.0

0.5

1.0

1.5

2.0

2.5

3.0

200 400 600 800 1000 1200 1400 1600 1800

ZrO2-8wt%Y

2O

3 plasma-sprayed porous coating

k measuredk fit due to lattice conduction-radiation

Ther

mal

con

duct

ivity

, W/m

-K

Surface temperature, °C

lattice conduction

radiation

sintering inducedconductivity rise

0

1

2

3

4

5

200 400 600 800 1000 1200 1400 1600

La2Zr

2O

7 sol-gel hot-press

La2Zr

2O

7 sol-gel hot-press

La2Zr

2O

7 hot-press

Ther

mal

con

duct

ivity

, W/m

-K

Surface temperature, °C

increasing porosity

La2Zr2O7

NA

SA/T

M—

2005-21343728

Evaluation of Radiation Thermal Conductivity of T/EBC Systems at High Temperatures

— Radiation conductivity increases with thermal gradient and thus heat flux

— Advanced HfO2 coatings demonstrated improved radiation resistance compared to the baseline ZrO2-8wt%Y2O3 coating

Dense materials

Plasma-sprayed coatings0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000 1200

Dense materials-1100°CDense materials-1200°CDense materials-1300°CDense materials-1400°C

Coatings-1550°CCoatings-1600°CCoatings-1650°CCoatings-1700°C

Rad

iatio

n co

mpo

nent

, (k a

ppar

ent-k

latti

ce)/k

latti

ce

Thermal gradient, K/mm

Dense materials

Plasma-sprayed coatings0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000 1200



Rad

iatio

n co

mpo

nent

, (k a

ppar

ent-k

latti

ce)/k

latti

ce


0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000 1200



Rad

iatio

n co

mpo

nent

, (k a

ppar

ent-k

latti

ce)/k

latti

ce


-1.6

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.00 0.02 0.04 0.06 0.08 0.10 0.12

ZrO2-8wt%Y

2O

3

HfO2-Y

2O

3

HfO2-(Y,Nd,Yb)

2O

3

HFO2-(Y,Gd,Yb)

2O

3+NiO+Al

2O

3

HfO2-(Y,Nd,Yb)

2O

3+NiO-Al

2O

3

0 200 400 600 800 1000 1200

ln(q

rad/q

rad0

)

Coating thickness, cm

Coating thickness, microns

NA

SA/T

M—

2005-21343729

Summary and Conclusions

• Advanced testing approaches established for ceramic coating development

• Real-time monitoring of coating thermal conductivity demonstrated as an effective technique to assess coating performance under simulated engine heat flux conditions

• The multi-component TBCs demonstrated lower conductivity, improved high temperature stability and cyclic durability required for advanced turbine airfoil and combustor applications

• High toughness erosion resistant turbine airfoil TBC developmentshowed significant progress

• Advanced 1650 °C (3000 °F) T/EBC systems developed forSi-based ceramics

NA

SA/T

M—

2005-21343730

This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

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Available electronically at http://gltrs.grc.nasa.gov

March 2005

NASA TM—2005-213437

E–14972

35

Thermal and Environmental Barrier Coatings for Advanced Turbine EngineApplications

Dongming Zhu and Robert A. Miller

Thermal barrier coatings; Environmental barrier coatings; Thermal radiation;Thermal conductivity; Defect clustering

Unclassified -UnlimitedSubject Categories: 23, 24, and 27 Distribution: Nonstandard

WBS–22–714–20–09

Viewgraphs prepared for the 2004 Fall Meeting sponsored by the Materials Research Society, Boston, Massachusetts,November 29–December 03, 2004. Dongming Zhu, U.S. Army Research Laboratory, NASA Glenn Research Center;and Robert A. Miller, NASA Glenn Research Center. Responsible person, Dongming Zhu, organization code RMD,216–433–5422.

Ceramic thermal and environmental barrier coatings (T/EBCs) will play a crucial role in advanced gas turbine engine

systems because of their ability to significantly increase engine operating temperatures and reduce cooling requirements,

thus help achieve engine low emission and high efficiency goals. Advanced T/EBCs are being developed for the low

emission SiC/SiC ceramic matrix composite (CMC) combustor applications by extending the CMC liner and vane tempera-

ture capability to 1650 °C (3000 °F) in oxidizing and water vapor containing combustion environments. Low conductivitythermal barrier coatings (TBCs) are also being developed for metallic turbine airfoil and combustor applications, providing

the component temperature capability up to 1650 °C (3000 °F). In this paper, ceramic coating development considerationsand requirements for both the ceramic and metallic components will be described for engine high temperature and high-

heat-flux applications. The underlying coating failure mechanisms and life prediction approaches will be discussed based

on the simulated engine tests and fracture mechanics modeling results.

thermal and environmental barrier coatings for advanced … · 2016. 10. 26. · thermal and...

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