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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
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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
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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
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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
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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
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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
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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
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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.
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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)
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-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
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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
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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
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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
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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
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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 +=
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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
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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