ENVIRONMENTAL BARRIER COATINGS FOR TURBINE ENGINES: A DESIGN AND PERFORMANCE PERSPECTIVE

Dongming Zhu, Dennis S. Fox, Louis Ghosn, James L. Smialek, and Robert A. Miller

NASA Glenn Research Center, USA

Ceramic thermal and environmental barrier coatings (TEBC) for SiC-based ceramics will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. However, the coating long-term durability remains a major concern with the ever-increasing temperature, strength and stability requirements in engine high heat-flux combustion environments, especially for highly-loaded rotating turbine components. Advanced TEBC systems, including nano-composite based HfO2-aluminosilicate and rare earth silicate coatings are being developed and tested for higher temperature capable SiC/SiC ceramic matrix composite (CMC) turbine blade applications. This paper will emphasize coating composite and multilayer design approach and the resulting performance and durability in simulated engine high heat-flux, high stress and high pressure combustion environments. The advances in the environmental barrier coating development showed promise for future rotating CMC blade applications.

https://ntrs.nasa.gov/search.jsp?R=20130013152 2018-05-11T23:22:08+00:00Z

National Aeronautics and Space Administration

Environmental Barrier Coatings for Turbine Engines: A Design and Performance Perspective

Environmental Barrier Coatings for Turbine Engines: A Design and Performance Perspective

Dongming Zhu, Dennis S. Fox, Louis Ghosn, James L. Smialek, Robert A. Miller

Durability and Protective Coatings BranchMaterials and Structures Division

NASA John H. Glenn Research Center

This work was supported by NASA Fundamental Aeronautics ProgramsThe 33rd International Conference on Advanced Ceramics & Composites

Cleveland, Ohio 44135, USA

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The 33rd International Conference on Advanced Ceramics & CompositesDaytona Beach, Florida

January 18-23, 2009

National Aeronautics and Space Administration

Revolutionary Ceramic Coatings Greatly Impact Turbine Engine TechnologyEngine Technology

— Ceramic barrier coatings can significantly increase gas temperatures, reduce cooling requirements, improve engine fuel efficiency and reliability

Combustor Vane Blade Ceramic nozzlesCombustor Vane Blade Ceramic nozzles

>300°F increase

Turbineincrease

CMC combustor liner and vaneliner and vane

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

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Revolutionary Ceramic Coatings Greatly Impact Turbine Engine TechnologyEngine Technology

— Ceramic barrier coating system development goals- Meet next generation engine temperature, performance and durability requirements- Help fundamental scientific understanding, database and design tool development- Increase the coating Technology Readiness Levels (TRL)

Temperature Capability (T/EBC) surface

Temperature Capability (T/EBC) surface

3000°F+ (1650°C+)p y ( )

Increase in ∆T across T/EBC

p y ( )

Increase in ∆T across T/EBC Si N and coating systems

2700°F (1482°C)

2400°F (1316°C)

G IV

Single Crystal Superalloy

Ceramic Matrix Composite

G IV

Single Crystal Superalloy

Ceramic Matrix Composite

Si3N4 and coating systems

2000°F (1093°C)

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Gen I

Gen II – Current commercialGen III

Gen. IV

YearGen I

Gen II – Current commercialGen III

Gen. IV

Year

National Aeronautics and Space Administration

Outline

─ High-heat-flux and simulated engine test approaches for ceramic coating development

─ The 2700°F thin turbine TEBC systems for SiC/SiC CMCs and Si3N4

─ Coating durability and stability evaluations

─ Summary and directions

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High-Heat-Flux Testing Approach– High-heat-flux tests crucial for the coating development

• Temperature gradient requirements: 400-600°F across 5-10 mil coatings

NASA CO Laser RigNASA CO2 Laser Rig

T

Heat flux cooling

Distance from surface

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Current capability up to 315 W/cm2 for TBCs

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High Pressure Burner Rig for Thermal and Environmental Barrier Coating DevelopmentBarrier Coating Development

─ Realistic engine combustion environments for specimen and component testing

High Pressure Burner rig (6 to 12 atm)C t d t bi t t fi t

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Coated turbine vane test fixtures

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High Pressure Burner Rig for Thermal and Environmental Barrier Coating DevelopmentBarrier Coating Development

• High Velocity and High Pressure Burner Rig Testing – High velocity testing for ceramic specimens– Optimum heat flux regime determined

200 1000Chamber pressureGas velocityp g

140

160

180

600

800Heat flux

Gas velocity

, W/c

m2

si; g

as v

eloc

ity, m

/s

80

100

120

200

400Hea

t flu

x

Cha

mbe

r pre

ssur

e; p

60

80

010 15 20 25 30 35 40

Pressure difference in combustor and test chamber, psi

Combustion flow

TC

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seen from viewport

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Multi-Functionally Graded Environmental Barrier Coatings for Si-based Ceramic Componentsfor Si based Ceramic Components

– Multifunctionally Graded Materials for SiC/SiC CMC and Si3N4 applications

Hi h t bilit id it l ith d d i t l i t l b i• High stability oxide composite layer with graded interlayer, environmental barrier and advanced bond coats

• Alternating composition layered coatings (ACLCs) and nano-composite coatings

Advanced EBCsbond coats

Interlayer: Compositional layer graded system -compositeLow expansion, high strain tolerance HfO2 & RE aluminosilicates

SiC/SiC CMC or Si3N4

HfO2 and HfO2 composites

Doped mullite/HfO2with ACLC (Hf rich bands)

Increased Si activity

Increased dopant RE/Transition metal concentrations & increased Al/Si ratio( )

Oxide and RE aluminiosilicate bond coats(High temperature capable with self-healing)

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Environmental Barrier Coatings Processed on Complex-Shaped SpecimensShaped Specimens

─ Thinner coating processing technologies developed for complex shaped components

Plasma-spray processing of Environmental barrier coatings for

various components

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Thin Turbine Blade CMC Coatings will be Pursued using Hybrid Plasma Vapor Deposition TechniqueHybrid Plasma Vapor Deposition Technique

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Sulzer plasma vapor deposition

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TEBCs Evaluated for Thermomechanical Fatigue (TMF) ResistanceResistance

-10 Hz, R ratio ~0, maximum mechanical load 250 MPa (36ksi) at 2200°F- Coating achieved excellent durability without failure after 250 hour testing- The system durability is currently limited by the CMC TMF capability and variabilityy y y y p y y

1.6 in

(a) Specimen testing (b) Specimen failure

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National Aeronautics and Space Administration

TEBCs Evaluated for ThermoMechanical Fatigue (TMF) Resistance - ContinuedResistance - Continued

300

coating

0

100

200

s, M

Pa

coating

-200

-100

Stre

s

-3000 0.5 1 1.5 2 2.5

Distance from surface, mm

Max 250 CMC MPa@2200°F, cyclic;

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CMC temperature modeling

@ , y ;Failed at 5x105 cycles

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Long-Term High Heat Flux Thermal Gradient Cyclic Testing of an Advanced TEBC Coating on SiC/SiC

Ceramic Matrix Composite- Coating successfully tested at Tsurface 2700°F and Tinterface 2400°F 250 hrs (1 hr hot hour cycles in air)

5.0

6.0

1600

y, W

/m-K

3 0

4.0

5.0

1200

Tsurfacecond

uctiv

ity

atur

e, °C

Tback=~1316°CTsurface=~1482°C

2.0

3.0

400

800

kcera

TsurfaceTinterfaceTback

zed

ther

mal

c

Tem

pera

Thin coating turbine CMC demonstrated high-heat-flux

0.0

1.0

0

400

0 50 100 150 200 250 300

Nor

mal

iz

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gcyclic durability at 2700˚F

0 50 100 150 200 250 300Time, hours

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High Pressure Burner Rig Durability Evaluations

- High Pressure Burner Rig Stability being evaluated for TEBCs on SiC/SiC- High stability coatings being down-selected

1AS800SN2822 -h

1300Temperature, °C

14001500 12001600

SiC/SiC under high velocity

0.1

SiC/SIC CMCLa

2Hf

2O

7

HfO2 (doped)

RE-Hf-luminosilicatesBSASan

ge, m

g/cm

2

0.01

c w

eigh

t cha Rare earth silicates

BSAS Baseline

0.0010 0005 0 00055 0 0006 0 00065 0 0007 0 00075 0 0008

Spec

ific

Future EBC stability development goal

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0.0005 0.00055 0.0006 0.00065 0.0007 0.00075 0.00081/T, K-1

National Aeronautics and Space Administration

Summary• Advanced ceramic turbine component testing capabilities established

• Advanced thermal and environmental barrier coatings developed and• Advanced thermal and environmental barrier coatings developed and processed on complex-shaped components

• Coating stability demonstrated in high velocity-high pressure burner rigCoating stability demonstrated in high velocity high pressure burner rig simulated engine environments

• Coated CMC system low cycle fatigue durability demonstrated at 2700˚Fy y g y

• Coated CMC system TMF evaluated at 2200°F

• Heat transfer, fracture mechanics and stochastic approaches being established to develop coated CMC life prediction models

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AcknowledgementThe work was supported by NASA Fundamental Aeronautics

Program, Supersonics Project.

The authors are grateful to Bob Pastel for performing the high pressure burner rig tests.

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