Slurry-Based Environmental Barrier Coatings Title - Arial 28pt
Transcript of Slurry-Based Environmental Barrier Coatings Title - Arial 28pt
Title - Arial 28pt
Slurry-Based Environmental Barrier Coatings
Kang N. Lee, Bryan J. Harder, Gustavo Costa*, and Bernadette J. Puleo
NASA Glenn Research Center, Cleveland OH
*Vantage Partners, Cleveland, OH
CIMTEC 2018, Perugia Italy
June 4-8, 2018
This work was supported by NASA Transformational Tools and Technology and Advanced Air Transport Technology programs
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Title - Arial 28pt
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Implementation of ceramic matrix composite (CMC) in Gas Turbines
Combustor
linersBladetrack
(Shroud)
Blades
Vanes
• CFM International LEAPx: HPT* Shroud in A320neo (2016) & B737max (2017)
• GE 9X: Combustor Liner, HPT* Shroud, HPT* Vanes in B777x (~2019)
* High Pressure Turbine
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L,--1 .__ ___________ .__ ________ __. '---~----,---Ar t Col'T'f)ressor 8chalst
Cold Section
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Evolution of Environmental Barrier Coatings (EBCs) at NASA
H2O(g) Si(OH)4(g) H2O(g) H2O(g)
• An external coating to protect CMCs from recession by H2O
• Enabling technology for CMCs
Gen 1 EBC (EPM: NASA-GE-PW-1997)
Gen 2 EBC(UEET: NASA-2003)
Silicon Bond Coat, mp = 1416oC(2580oF)
K. N. Lee, Surf. and Coat. Tech, 133-134 1-7 (2000).
Yb2Si2O7
SiCMC
CMC Recession
E. J. Opila et al., Am. Ceram. Soc., 80[1], 197-205 (1997)
: gas velocity
P(H2O) : water vapor pressure
PTOTAL : total pressure
SiO2 (s) + 2H2O (g) = Si(OH)4 (g)
EBC
Mullite Coating(NASA-1993)
K. N. Lee et al. ," J. Am. Ceram. Soc., 78(3) 705-710 (1995).
Next Gen EBC
(NASA Developmental)
CMC
EBC
2700oF (1482oC) Bond Coat
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Volatility oc v x P(H20) 2
(PTOTAL ) 112
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• Develop next Gen EBCs with 2700oF (1482oC) bond coat capability using slurry process
• Bond coat: Yb2Si2O7-Based, Mullite-Based
• Sintering aids: Oxide-based
• Validation: Steam cycling rig, Combustion rigs
Objective
Yb2Si2O7
Steam Cycle, 1350oC, 90% H2O, 100h
TGO ~10mm
Feasibility Demonstrate of
Slurry EBC (mid 2000’s)
Cleveland State Univ./NASA (J. Euro. Ceram. Soc., 1123-1130, 2011)
Planetary Mill (Submicron coating
powders)
Organic processing aids
(Coating powders+ Processin aids +Solvent
Processing (Dip, Spin-Dip, Spraying)
Drying (Burnout organic
Sintering (Consolidate coating)
Particle size analysis
Zeta otential
Dilatometer
Test & Characterization
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Lift
Cycle
Temp Up to "'2700F
Velocity "'10 cm/s
Water vapor Up to "'0.9 atm
Pressure latm
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5,366-h GE Shroud Rig Test 15,144-h Solar Combustor Liner Engine Test
GE Final Report – DOE AMAIGT Program, Dec. 2010J. Kimmel et al., ASME paper GT2003-38920, ASME TURBO EXPO, Atlanta, GA, USA, June 16-19, 2003.
Key EBC Failure Mode: Oxidation-Induced Spallation
• Water vapor (H2O) is the primary oxidant
• SiO2 TGO (thermally grown oxide) forms due to Si bond coat oxidation
• Growth stress (~2.2x volume expansion)
• Phase transformation stress (~5% volume expansion due to b to a cristobalite at ~200oC)
• CTE* mismatch stress (a cristobalite =10.3 x 10-6/C vs. Yb2Si2O7 = 4.7, Si = 4.4, SiC = ~5)
• Causes large residual stresses that provide the strain energy release rates required to drive EBC delamination cracks
*Coefficient of thermal expansion
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100h/100 cycles
500h
As-Sintered
CMC CMC
100h
TGO
TGO
Bond Coat
Top Coat
80 mm
80 mm
20 mm
As-Sintered
Bond Coat
Top Coat
Bond Coat
Top Coat
• Yb2Si2O7-based top coat for recession resistance• Sintered at T>2700oF (1482oC)• Excellent microstructural & chemical stability • EBC remained adherent after 500h
Slurry EBC w/ Yb2Si2O7-Based Bond Coat
[Steam Oxidation: 1 hr at 2600oF (1427oC) / 20 min at T<100oC, 90% H2O]
TGO
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100h
CMC
Chem Barrier
Top Coat
Bond Coat
As-Sintered Bond Coat
CMC
80 mm
20 mm
500h
80 mm
TGO
CMCTGO
Chem Barrier
Top Coat
Bond Coat
• Yb2Si2O7-based top coat for recession resistance•HfSiO4-based chemical barrier
• Yb2Si2O7-Mullite Eutectic = ~1500oC
• Sintered at T> 2700oF (1482oC)• Excellent microstructural & chemical stability• EBC remained adherent after 500h
Slurry EBC w/ Mullite-Based Bond Coat
[Steam Oxidation: 1 hr at 2600oF (1427oC) / 20 min at T<100oC, 90% H2O]
TGOTGO
~ J .., . :; ~ ... ",.) ..... • ..,,.., • • -., ;- • I (iJ •, ~ ~;,• •·._ .,, ...... ~ ' .,
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Time, Hrs
CMC
Yb2Si2O7-Based EBCMullite-Based EBCInternal Surface
Si (10% O2)*
* Extrapolated from Deal and Grove, J. Appl. Phys., 36[12] 3770-78 (1965)
Steam Oxidation Rates of Slurry EBCs in Steam Cycling[2700oF (1482oC) in 90% H2O+10% O2, 1h cycles]
• Both slurry coatings provide substantial mitigation of steam oxidation• Mullite-based bond coat shows slightly lower TGO growth rates
• TGO is thicker on the internal surface (~25%) than under the EBC• Oxidation mechanism studies in progress
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30
Ill C 25 e
.!::! ~ 20 .. Ill Ill a, C
,.:=.:: 15 .!::! .c l-o 10
~ 5
0 • ~
, , , ,
, , , ,
, , , , ,
, , , , , --
I
------__ ... -------* --o+ 10% O_i~----------. 10.0°lo \-\1. ------
S\ ''? ------------------
0 ~ •
-----------------------------0 n-........ -,.,,-:..::-:..::-___________________________ _ 0 100 200 300 400 500
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Parabolic Oxidation Plot of Slurry EBCs[1 hr at 2600oF (1427oC) / 20 min at T<100oC, 90% H2O]
Substrate CVI* CMC CVI* CMC CVI* CMC
Coating Yb2Si2O7-Based Mullite-Based Uncoated(Internal Surface)
k (mm2/h) 0.70 0.47 2.11
• Parabolic rate constant is ~50% higher with Yb2Si2O7-Based bond coat• Uncoated CMC (Internal surface) shows ~2x – 3.5x higher parabolic rate
constant than coated CMC
YbDS-Based EBC
Mullite-Based EBC
*Chemical vapor infiltration
450 r-J
E 400 :::i.
350 r-J - 300 Vl
C
~ 250 u
£ 200
I- 150 0
~ 100
- so 0
.. . ... .... \~~-_. ............... a·· 0 100
k =0.7043 O
.... •·~
ij ....................... •····: .... -o -··Q ······· ········
W•·········· ··•' .... k = 0.4705 .... •· ········· ····· ····· ......
200 300
Time, Hrs
400 500
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Spin-Dip CoaterSlurry EBC-coated
3”x3” CMC Airfoil
• Durability testing in a combustion rig at 2500oF-2700oF (1371-1482C) is in progress• Steam cycling test of witness coupons at 2600oF (1427C) in progress
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EBC on Monolithic SiC (3”x 3”) – 1st Airfoil Spin-Dip Trial
As-Coated
100h-100 cycles at 2700oF in Air
Leading
Edge
Trailing
Edge
20 mm
• Demonstrated 2700oF (1482C) temperature capability in air cycling• SiC substrate broke due to thermal shock
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Slurry EBC Fabrication on Mini-composite (via Air Brush)
As-Deposited and Dried(Fractured Surface)
As-Sintered(Polished Surface)
Top Coat
Bond Coat
Top Coat
Bond Coat
• Steam oxidation and mechanical testing in progress
100 mm
200 mm
30 mm
30 mm
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Time, hr
Uncoated, Air
Coated, Steam
Coated, Air
Cyclic Oxidation of Slurry EBC on SiC Heating Element(1 hr at 2600oF (1427oC) / 20 min at T<100oC, 90% H2O)
• High oxidation rate of uncoated SiC due to additives and high porosity • EBC is effective in reducing oxidation rate in air and steam
SiC
EBC
EBC
We
igh
t g
ain
. m
g/c
m2
100 mm
30 mm
SiC
5
4
3
2
1
0 0 20 40
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60 80 100
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Conclusion
Two slurry-based EBCs capable of 2700oF have been developed
Low-cost, non-line-of-sight EBC technology
Coating can be readily applied on components of various complexities
and shapes
Coated coupons demonstrated 500h-500 cycle steam oxidation
durability at 2600oF (1427C)
Parabolic oxidation rate is ~1/3 of the rate on uncoated internal CMC surface
Coated SiC airfoil demonstrated 100h-100 cycle cyclic durability in
air at 2700oF (1482C)
A spin-dip coating process developed for airfoils
Coated CMC airfoil combustion rig test at 2500oF-2700oF (1371-
1482C) in progress
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Title - Arial 28pt
Deborah Waters for the initial development work of slurry
EBCs (NASA GRC)
John Setlock for air brush spraying of slurry EBC on mini-
composites (University of Toledo)
Dagny Sacksteder for testing of EBC-coated SiC heating
elements (Summer Intern, The Ohio State University)
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Acknowledgement •