NASA Technical Reports Server (NTRS) 20170005264: Thermochemistry of CaO-MgO-Al2O3-SiO2 (CMAS) and Advanced Thermal and Environmental Barrier Coating Systems

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by  NASA Technical Reports Server (NTRS)

National Aeronautics and Space Administration
Thermochemistry of CaO-MgO-Al O -SiO (CMAS) and
2 3 2
Advanced Thermal
and Environmental Barrier Coating Systems
GUSTAVO COSTA AND DONGMING ZHU
Environmental Effects and Coatings Branch
Materials and Structures Division
NASA Glenn Research Center, Cleveland, OH 44135
[email protected]
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Outline of Presentation
• Thermal and Environmental Barrier Coating Systems
• Experimental
- Sample preparation and reaction with CMAS
• Results
-
Thermodynamic modeling of YSZ-CMAS system
- Characterization:
1 - Pristine NASA composition CMAS by XRD, ICP-OAS and DSC
2 - CMAS reacted with the hollow tube coating specimens by SEM-EDS and XRD
• Summary
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Thermal and Environment Barrier Coating Developments
Baseline ZrO -(7-8)wt%Y O and Rare Earth Doped-Low Conductivity Thermal Barrier
2 2 3
Coating Systems - Continued
Baseline ZrO -(7-8) wt%Y O :
2 2 3 Ceramic coating
- Relatively low intrinsic thermal conductivity ~2.5 W/m-K
NiCrAlYBond coat
- High thermal expansion to better match superalloy substrates
- Good high temperature stability and mechanical properties
-Additional conductivity reduction by micro-porosity
Low Conductivity Defect Cluster Thermal Barrier Coatings
— Multi-component oxide defect clustering approach
e.g.: ZrO /HfO -Y O -Nd O (Gd O ,Sm O )-Yb O (Sc O ) systems
2 2 2 3 2 3 2 3 2 3 2 3 2 3
Primary stabilizer
Oxide cluster dopants with distinctive ionic sizes
— Defect clusters associated with dopant segregation
— The 5 to 100 nm size defect clusters for significantly reduced thermal conductivity (0.5-1.2 W/m-K)
and improved stability
Plasma-sprayed ZrO -
— Advanced TEBC systems for Ceramic Matrix Composites use the low k based compositions 2
(Y, Nd,Yb) O
2 3
TEBCs-CMAS Degradation is of
Concern with Increasing
Operating Temperatures
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Experimental:sample preparation and heat treatment
• Air plasma sprayed coating (0.030” thickness) specimens on to 1/8” diameter graphite bar substrates
then 1500 C, 5 h sintering, resulting hollow tubes.
• NASA composition CMAS used for reaction at 1300  C for 5h.
Hollow Tube composition mole (%) r(%) * Average
pore vol.
3 mm -cut (mm3) **
Pt foil
ZrO -12Y O 90(3) 35(2)
2 2 3
ZrO - 18Y O 81(3) -
XRD and 2 2 3
cubic
SEM-EDS HfO -7Dy O 89(3) 21(3)
CMAS 2 2 3
ZrO - 9Y O - 4.5Gd O - 4.5Yb O 100 (3) 3(7)
powder
2 2 3 2 3 2 3
3 mm -cut ZrO - 9.6Y O - 2.2Gd O - 2.1Yb O 90(3) 23(4)
2 2 3 2 3 2 3
ZrO - 3Y O - 1.5Nd O - 1.5Yb O - 0.3Sc O 90(3) 20(3)
2 2 3 2 3 2 3 2 3
tetragonal
ZrO - 3Y O -1.5Sm O -1.5Yb O 98(3) 4(3)
2 2 3 2 3 2 3
*(rgeometric*100/rHe). **rgeometric-rHe.
(1:10 CMAS to sample mass ratio, concentration of 70-150 mg/cm2)
(A) (B) (C)
Hollow 12YSZ tube samples: (A) pristine; (B) before heat treatment in which it was half filled with CMAS
powder, wrapped and sealed with Pt foil; (C) after heat treatment at 1310 C for 30 min and unwrapped.
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Results: characterization of NASA composition CMAS (as processed) before reaction
Phase content (Wt. %) Chemical analysis of the as-received NASA CMAS by ICP-OAS
Amorphous – 66.4  0.9
Element Amount(wt. %) ±
SiO – 3.5  0.1
2
Ca 21 1
Ca Mg Al Si O – 23.5  0.7
2 0.46 0.99 1.52 7 Mg 3.1 0.2
CaSiO – 6.6  0.4
3 Al 6.1 0.3
Si 19 1
Fe 5.9 0.3
Ni 1.10 0.06
Trace elements found but not quantified are
Ba, Cr, Cu, K, Mn, Na, Sr, Ti, Zr
DSC /(mW/mg) Complex Peak: Flow /(ml/min)
Area: -48.79 J/g
exo Peak: 1319.3 °C
Onset:1258.2 °C
End: 1329.5 °C 250
X-ray diffraction patterns of theas-received CMASsample. 0.0
200
-0.2
-0.4
150
-0.6
100
-0.8
50
-1.0
-1.2 0
200 400 600 800 1000 1200 1400
Temperature /°C
Main
Instrument :NETZSCH DSC 404F1File :C:\NETZSCH\Proteus\data5\Costa\Samples\G64.dd8Remark :Third DSC run since Oct 2014. 1x evac/backfill
ProjDect :SC traces of CRefeMrenceA : SR emf Al2Oi3x,0 megd with 18YSZ (1:2 Mmode/atypse osf m erasa. :tDiSoC / )sa mdpleu witrh cionrrecgtion
Identity : G64 Material : Segments : 1/1
DSC traces of CMAS during heating and cooling up to Date/time : 6/30/2016 4:20:39 PM Corr./temp.cahl :ebaaselitnei 1n500gC 10Cu _mpin _0t6o-30- 116.bd58 / 0TCA0LZ EROC.TM Xat Crucible : DSC/TG pan Pt
Laboratory :Glenn Research Center Sens.file : sensitivity from sapphire_Pt crucible 1500C air 01-06-16.ed8 Atmosphere : N2/O2, 50.0ml/min
Operator : Costa Range : 20/10.0(K/min)/1500 Corr/m. range : 020/5000 µV
1500 C at 5 C/min. Sample : G64, 24.8 mg Sample car./TC :DSC Cp S / S 5 C/min.
Created with NETZSCH Proteus software
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Results: Thermochemical modeling of YSZ – CMAS system using
National Aeronautics and Space Administration
Thermocalc and TCOX6 database
Reaction T of the experiments
Calculated phase diagram
of CMS-YSZ system.
Input oxide amounts
Component Mole
CaO 35
MgO 8
AlO 7
2 3
SiO 45
2
FeO 3
2 3
NiO 1
ZrO 82
2
YO 18
2 3
8 mol% Y O
2 3
Fluoride ZrO2_tetragonal
2.3 mol% Y O Ionic_liq#2
2 3 Output: Component Mol
Baseline TBC T - 1316.85 C CaO 1.7e-2 Mol Apatite Mol
Component Component
MgO 2.5e-3
CaO 8.1e-3 Mol CaO 2.8e-1
FeO 1.7e-7
1.5 MgO 5.1e-5 Component MgO 9.3e-2
AlO 1e-3
1.5 FeO 8.6e-8 CaO 1.1e-1 SiO 3.8e-1
NiO 4.4e-3 1.5 2
NiO 3.8e-3 MgO 2e-4 FeO 9.3-1
SiO 3.0e-5 1.5
2 ZrO 9.7e-1 SiO 2.7e-1 NiO 2.2e-2
ZrO 8.9e-1 2 2
2 YO 1.8e-2 YO 6.2 e-1 ZrO 2.7e-2
YO 8.4e-2 1 1.5 1 1.5 2
1 1.5
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Results: SEM cross-section images at low magnification (lower cut section)
12YSZ 18YSZ 7DySH
ZrO -9.0Y O -4.5Gd O -4.5Yb O ZrO -9.6Y O -2.2Gd O -2.1Yb O ZrO -3.0Y O -1.5Sm O -1.5Yb O
2 2 3 2 3 2 3 2 2 3 2 3 2 3 2 2 3 2 3 2 3 ZrO -3.0Y O -1.5Nd O -1.5Yb O -
2 2 3 2 3 2 3
0.3Sc O
2 3
SEM cross – sectional electron images of the lower section of the ceramic hollow tube samples reacted
with CMAS at 1300 C for 5 h.
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Results: 12YSZ lower section of the hollow tube reacted with CMAS.
Spots 1-3.
SEM image of (reacted region) at high magnification.
Grains 1-3 ZrO Y O
2 2 3
Nominal mole (%) 88 12
EDS mole (%) 81 (1) 11.9(2)
cubic, YSZ
Spot 4.
XRD pattern of the ground hollow tube. Elemental content from EDS.
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Results: 18YSZ lower section of the hollow tube reacted with CMAS.
Spot 2.
Spot 1.
SEM image at high magnification.
Grain 1 ZrO Y O
2 2 3
Nominal mole (%) 81 18
EDS mole (%) 75(2) 19(1)
Spot 3.
cubic, YSZ + apatite phases
X-ray diffraction of the ground hollow tube. Elemental content from EDS.
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Results: 7DySH lower section of the hollow tube reacted with CMAS.
Spot 2.
SEM image at high magnification.
Grain 2 HfO Dy O
2 2 3
Nominal mole (%) 93 7
EDS mole (%) 85(5) 7(1)
Monoclinic and cubic, DySH
Spot 1.
XRD pattern of the ground hollow tube. Elemental content from EDS.
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