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Luminescence-Based Diagnostics of Thermal Barrier Coating Health and Performance

Jeffrey I. Eldridge NASA Glenn Research Center

Cleveland, OH

National Aeronautics and Space Administration

37th International Conference on Advanced Ceramics & Composites Daytona Beach, FL January 29, 2013

https://ntrs.nasa.gov/search.jsp?R=20130011545 2018-08-20T04:59:01+00:00Z

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Acknowledgments

NASA GRC Dongming Zhu (High heat flux testing) Tim Bencic (2D surface temperature mapping) Joy Buehler (Metallography)

Penn State Doug Wolfe (EB-PVD)

U. Connecticut Eric Jordan (SPPS)

Metrolaser Tom Jenkins (VAATE engine test team)

Emerging Measurements Steve Allison (VAATE engine test team)

Funding by NASA Fundamental Aero and Air Force Research Laboratory.

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Motivation Address need to test & monitor performance & health of TBCs.

Lab environment assessment tool Engine environment validation tool

Essential for safely increasing engine operating temperatures.

Approach: Luminescence-Based Monitoring of TBC Performance

Multifunctional TBCs with integrated diagnostic capabilities Erosion monitoring Delamination progression monitoring Temperature sensing

Above & below TBC Engine environment implementation 2D temperature mapping

TBC Translucency Provides Window for Optical Diagnostics

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1 mm thick 13.5 YSZ single crystal (transparent)

135 m thick Plasma-sprayed 8YSZ (translucent)

Backlit by overhead projector.

Light Transmission Through YSZ

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606 nm Eu3+ emission

Undoped YSZ YSZ:Eu YSZ:Tb

PtAl bond coat

Rene N5 superalloy substrate

UV illumination

543 nm Tb3+ emission

Erosion monitoring by luminescence detected from exposed YSZ:Eu and YSZ:Tb sublayers

Coating Design

Erosion Detection Using Erosion-Indicating TBCs

Erosion Depth Indication Using Eu- and Tb-Doped YSZ

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coating surface, white light illumination coating surface, UV illumination

erosion crater

Luminescence reveals location and depth of coating erosion.

1 cm 1 cm

165 m sublayer-doped 7YSZ/PtAl/Rene N5

*EB-PVD TBCs produced at Penn State, D.E. Wolfe.

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562 nm Er3+ emission (high intensity) 562 nm Er3+ emission

(low intensity)

980 nm illumination

Undoped YSZ

Er + Yb-doped YSZ

NiPtAl bond coat

Rene N5 superalloy substrate

delamination reflects excitation & emission

Detecting TBC Delamination by Reflectance-Enhanced Upconversion Luminescence

Two-photon excitation of Er3+ produces upconversion luminescence at 562 nm with near-zero background for strong delamination contrast.

Yb3+ absorbs 980 nm excitation and excites luminescence in Er3+ by energy transfer.

Delamination contrast achieved because of increased reflection of excitation & emission at TBC/crack interface.

upconversion

EB-PVD (Penn State)

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EB-PVD TBCs*

10 m 50 m

SEI BEI

YSZ YSZ:Er(1%),Yb(3%)

NiPtAl 6 m

130 m

Rene N5

YSZ:Er,Yb

Undoped YSZ

*EB-PVD TBCs produced at Penn State, D.E. Wolfe.

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Upconversion Luminescence Images During Interrupted Furnace Cycling for EB-PVD TBC with YSZ:Er(1%),Yb(3%) Base Layer

1cm

1 furnace cycle = 45min @1163C + 15 min cooling 7.5 sec acquisition 1 cycle 10 cycles 20 cycles 30 cycles 40 cycles 0 cycles 60 cycles 80 cycles 100 cycles 120 cycles

140 cycles 160 cycles 180 cycles 200 cycles 220 cycles 240 cycles 260 cycles 280 cycles 300 cycles 320 cycles

340 cycles 360 cycles 380 cycles 400 cycles 420 cycles 440 cycles 460 cycles 480 cycles 500 cycles 520 cycles

540 cycles 560 cycles 580 cycles 600 cycles 620 cycles

740 cycles

640 cycles 660 cycles 680 cycles 700 cycles 720 cycles

745 cycles YSZ YSZ:Er(1%),Yb(3%)

NiPtAl 6 m

130 m

Rene N5

Batch 1

10

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 100 200 300 400 500 600 700

Furnace Cycles

Lu

min

esce

nce

Inte

nsi

ty R

atio

#1 fails at 620 cycles#2 fails at 500 cycles#3 fails at 745 cycles

Change in Upconversion Luminescence Intensity with Furnace Cycling to TBC Failure

early indication of TBC life

Failure Progression EB-PVD TBC with YSZ:Er(1%),Yb(3%) Base Layer

400 cycles Bright spots produced by large-separation micro-delaminations between TBC & TGO produced by bond coat instabilities (rumpling).

Small microcracks between TBC & TGO increase intensity but may not be resolved individually

TGO growth during furnace cycling

Microdelamination + TGO growth

Delamination increases luminescence intensity. TGO growth decreases luminescence intensity.

Luminescence Image

10 m

200 cycles 10 m

700 cycles

10 m

30 cycles

10 m

0 cycles

10 m

1cm

200 cycles

10 m

Monitoring TBC Delamination Around Cooling Holes

TBC-coated specimen with 0.020 diam laser-drilled cooling holes at 20.

Problem: Cooling holes in turbine blades and vanes can act as

stress-concentrating failure initiation sites for surrounding TBC. Potential severity of these effects are unknown.

Objective: Determine the severity of the effect of cooling holes on the lifetime of surrounding TBC using upconversion luminescence imaging.

Approach: Performed luminescence imaging during interrupted furnace cycling of TBC-coated specimens with arrays of 0.020 diameter laser-drilled cooling holes.

20 hole pattern (typical angle for turbine blades)

Top view

Side view 20

Monitoring Delamination Around Laser-Drilled Cooling Holes by Upconversion Luminescence Imaging During Furnace Cycling

7.5 sec acquisition

280 cycles 300 cycles 360 cycle 340 cycles

1 furnace cycle = 45min @1163C + 15 min cooling

1 cm

YSZ YSZ:Er(1%),Yb(3%)

NiPtAl 12 m

130 m

Rene N5

320 cycles

400 cycles

380 cycle

420 cycles

White light image

460 cycles 480 cycles 500 cycles 520 cycles

Upconversion luminescence

image

440 cycles

Effect of Cooling Holes on TBC Life

Luminescence imaging easily detects delamination around cooling holes.

Local delamination does initiate around cooling holes but exhibits very limited, stable growth.

The unstable delamination propagation that leads to TBC failure actually AVOIDS vicinity of cooling holes.

Significance: Cooling holes in turbine blades and vanes do not shorten TBC life and their behavior as debond initiation sites can be tolerated safely.

Luminescence-Based Remote Temperature Monitoring Using Temperature-Indicating TBCs

Undoped YSZ

Eu-doped YSZ

PtAl bond coat

Rene N5 superalloy substrate

pulsed 532 nm illumination

Temperature (oC)

0 200 400 600 800 1000 1200

Asy

mp

toti

c D

ecay

Tim

e (

sec)

0.1

1

10

100

1000

10000

606 nm Eu3+ emission (with temperature-dependent decay)

-4

-3

-2

-1

0

1

2

0 1 2 3 4 5

Time (sec)

ln [

Em

issi

on

Inte

nsi

ty (

V)]

5 mil undoped YSZ/1 mil YSZ:Eu hitemp decay

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-5

-4

-3

-2

-1

0

0 1 2 3 4 5

Time (sec)

500 C550 C600 C620 C640 C660 C680 C700 C720 C740 C760 C780 C800 C820 C840 C860 C880 C900 C920 C940 C960 C980 C1000 C

Buried Eu-doped YSZ layer, Eu3+ luminescence decay

Surface Eu-doped YSZ layer, Eu3+ luminescence decay

Eu-doped YSZ

15

50 m

undoped YSZ (118 m)

YSZ:Eu (36 m)

Buried Eu-doped YSZ, Eu3+ luminescence image

PtAl

or

Decay Time vs. Temperature Calibration

NASA GRC High-Heat-Flux Laser Facility Proof-of-concept with easy optical access, no radiative background, no probe heating issues.

Williams International Combustor Burner Rig Address probe/TP survivability & ability to see through flame.

AEDC J85-GE-5 Probe/translate through afterburner flame. Opportunity to test excitation/collection integrated probe.

Demonstrated to 1360C.

Demonstrated to >1400C.

AFRL Versatile Affordable Advanced Turbine Engines (VAATE) Project Gas Turbine Engine Sensor and Instrumentation Development

Demonstrated to >1300C.

Goal: Demonstrate thermographic phosphor based temperature measurements to 1300C on TBC-coated HPT stator on Honeywell TECH7000 demonstrator engine.

Honeywell TECH7000

1E-05

0.0001

0.001

0.01

0 200 400 600 800 1000

PMT

Sign

al (V

)

Time (s)

2.5 mm6.9 mm11.2 mm15.7 mm20 mm24.4 mm28.8 mm33.1 mm

Distance from edge

Temperature Line Scan Across Hot Spot During Williams Combustor Burner Heating

Traversing High-Flame Hot-Spot Luminescence from YAG:Dy Coating

123

4

5

6

7

8

1

10

100

1000

0 200 400 600 800 1000 1200 1400 1600 1800

Deca

y Tim

e (

s)

Temperature (C)

range of confidence

High-Flame Temperature Line Scan

1

10

100

1000

1100

1150

1200

1250

1300

1350

1400

1450

1500

1550

1600

0 5 10 15 20 25 30 35

Deca

y Tim

e (u

sec)

Tem

pera

ture

C

distance from edge (mm)

substrate melting!

Luminescence emission observed

through 456 nm bandpass filter

Implementation of Ultra-Bright High-Temperature Phosphor

Breakthrough discovery* of exceptional high temperature retention of ultra-bright luminescence by Cr-doped GdAlO3 with orthorhombic perovskite crystal structure: Cr-doped gadolinium aluminum perovskite (Cr:GAP). High crystal field in GAP suppresses thermal quenching of

luminescence. Novel utilization of broadband spin-allowed emission extends

luminescence to shorter wavelengths where thermal radiation background is reduced.

Enables luminescence-based temperature measurements in highly radiant environments to 1250C. Huge advance over state-of-the-art ultra-bright luminescence

upper limit of 600C.

*J.I. Eldridge & M.D. Chambers

Demonstrating Temperature Measurement Capability Time-Averaged Luminescence Emission from Cr(0.2%):GAP Puck

Temperature Dependence

550 600 650 700 750 800 850

Inte

nsi

ty (a

rb.u

nit

s)

Wavelength (nm)

20C

90C

284C

385C

484C

587C

686C

780C

880C

977C

bandpass

Coatings for 2D Temperature Mapping Luminescence Decay Curves from 25 m Thick EB-PVD Cr:GAP

Coating

1E-05

0.0001

0.001

0.01

0.1

0.00E+00 1.00E-04 2.00E-04 3.00E-04 4.00E-04 5.00E-04

Inte

nsity

(V)

Time (sec)

482C588C

682C

785C

879C977C

1076C

Superb signal-to-noise from thin 25 m thick coating confirms retention of ultra-bright luminescence at high temperatures.

21 /2

/1 Fit to

tt eIeII +=

Demonstrating Temperature Measurement Capability

Calibration of Decay Time vs. Temperature for GAP:Cr Coating

Temperature (C)

200 400 600 800 1000 1200

Dec

ay T

ime

(sec

)

1e-7

1e-6

1e-5

1e-4

1e-3

1e-2

1e-1

kTEEqkTE

kTERE ee

e/)(/

/

2 1

31 Fit to +

+++

=

Two distinct regions 200C

2D Temperature Mapping of Effect of Air Cooling Jets

Laser heat flux

Air Jet Fixture for Laser Heat Flux Testing

4 cooling jets

nozzle

970C980C990C1000C1010C1020C1030C1040C 1050C

Sequence of gated images (Tim Bencic, NASA GRC) 2D Temperature Map (B&W) 2D Temperature Map (color)

Temperature (C)

200 400 600 800 1000 1200

Dec

ay T

ime

(sec

)

1e-7

1e-6

1e-5

1e-4

1e-3

1e-2

1e-1

Temperature determined from decay time at each pixel.

GAP:Cr Decay Time vs. Temperature Calibration

Insensitive to surface emissivity & reflected radiation!

1 cm

1 cm

Courtesy of Dongming Zhu, NASA GRC

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Summary

Luminescence-based sensing successfully monitors TBC health & performance. Erosion indication by self-indicating TBCs Delamination progression monitoring by upconversion

luminescence imaging Predictive for remaining TBC life Cooling hole debond initiation sites safely tolerated.

Temperature sensing by luminescence decay time behavior Surface & depth-penetrating measurements Ultra-bright high-temperature GAP:Cr phosphor enables 2D

temperature mapping.

Nearing engine-test-ready status.

Luminescence-Based Diagnostics of Thermal Barrier Coating Health and PerformanceAcknowledgmentsMotivationTBC Translucency Provides Window for Optical DiagnosticsSlide Number 5Erosion Depth Indication Using Eu- and Tb-Doped YSZ Slide Number 7EB-PVD TBCs*Slide Number 9Slide Number 10Slide Number 11Monitoring TBC Delamination Around Cooling HolesSlide Number 13Effect of Cooling Holes on TBC LifeSlide Number 15Slide Number 16Temperature Line Scan Across Hot SpotDuring Williams Combustor Burner HeatingImplementation of Ultra-Bright High-Temperature PhosphorDemonstrating Temperature Measurement CapabilityTime-Averaged Luminescence Emission from Cr(0.2%):GAP PuckTemperature DependenceCoatings for 2D Temperature Mapping Luminescence Decay Curves from 25 m Thick EB-PVD Cr:GAP CoatingDemonstrating Temperature Measurement CapabilityCalibration of Decay Time vs. Temperature for GAP:Cr Coating2D Temperature Mapping of Effect of Air Cooling JetsSummary