Reaction of Lanthanide Zirconate Pyrochlore Environmental Barrier ......
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Reaction of Lanthanide Zirconate Pyrochlore Environmental Barrier Coating Materials in CMAS Jeffrey W. Fergus 2015 Crosscutting Research Review Pittsburgh, PA 28 April 2015
Transcript of Reaction of Lanthanide Zirconate Pyrochlore Environmental Barrier ......
Reaction of Lanthanide ZirconatePyrochlore Environmental Barrier
Coating Materials in CMAS
Jeffrey W. Fergus
2015 Crosscutting Research ReviewPittsburgh, PA28 April 2015
Participants
• Auburn University– Jeff Fergus – Honglong (Henry) Wang – Ph.D. Student– Xingxing Zhang – Ph.D. Student– Emily Tarwater – Undergraduate Student– Sudip Dasgupta – Visiting Scholar (Summer 2014)
• Plasma Processes LLC– Kyle Murphree– Tim McKechnie
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Bond coat system
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• Collaboration with Plasma Processes LLC
• Alternative bond coat layers• YSZ / zirconate coatings
http://www.plasmapros.com/
Thermal barrier coating system
TBC: YSZ and/or pyrochlore
Alloy: 738LC
Ir (50-100 μm)Re diffusion layer
Hf (25-50 μm)
Flash Ni coating
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Plasma spray for YSZ / pyrochlore
Molten salt electrochemical deposition (El-Form®) for Re/Hf/Ir
Approach
• Coating development– Evaluate need for Ni coating– Optimize Hf/Ir for YSZ – Feasibility Hf/Ir for pyrochlore– YSZ + pyrochlore
• Coating materials– Stability of pyrochlore in CMAS
• Gd2Zr2O7, Sm2Zr2O7, mixed
– Accelerate with high temperature exposures
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Need for nickel layer
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TBC: YSZ and/or pyrochlore
Alloy: 738LC
Ir (50-100 μm)Re diffusion layer
Hf (25-50 μm)
Flash Ni coatingEvaluate possible elimination of Ni coating
?
Rhenium coating with/without nickel
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With Ni LayerWithout Ni Layer
Nickel coating needed
Iridium coatings on round samples
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2 out of 20 iridium coatings good quality
Electrochemical deposition reveals non-
visible defects in Re coating
Iridium coatings on rectangular samples
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Rectangular coatings for mechanical testing
Revised approach
• Electrochemical deposition process sensitive to defects in substrate coating
• Focus coating efforts on environmental barrier coatings
• Plasma-sprayed materials to corroborate results from sintered ceramics
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Pyrochlore coating materials
• Reaction with CMAS• Thermal conductivity
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Reaction with CMAS
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La2Zr2O7
YSZ + La2Zr2O7
YSZ
C.S. Ramachandran et al., Ceram. Int. 39, 1413 (2013)
Thermal conductivity of zirconia with 7-8% yttria
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
200 400 600 800 1000 1200 1400 1600
[ 13 ] [ 13 ] [ 14 ] [ 14 ] [ 15 ] [ 16 ]
[ 17 ] [ 18 ] [ 19 ] [ 20 ] [ 21 ] [ 21 ]
[ 21 ] [ 22 ] [ 23 ] [ 23 ] [ 23 ] [ 24 ]
[ 25 ] [ 26 ] [ 27 ] [ 28 ] [ 29 ] [ 30 ]
Temperature (K)
Thermalcond
uctiv
ity (W
m‐1K‐
1 )
Range of thermal conductivities due to variations in morphology and microstructure
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J. Fergus. Met. Mater. Trans E 1, 118 (2014).
Thermal conductivity of Gd2Zr2O7
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
200 400 600 800 1000 1200 1400 1600
[ 16 ] [ 18 ] [ 55 ]
[ 56 ] [ 56 ] [ 58 ]
[ 59 ] [ 60 ] [ 61 ]
Temperature (K)
Thermalcond
uctiv
ity (W
m‐1K‐
1 )
7‐8 wt% YSZ from Figure 1 κ of Gd2Zr2O7
in lower range of YSZ
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J. Fergus. Met. Mater. Trans E 1, 118 (2014).
Thermal conductivity of Sm2Zr2O7
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
200 400 600 800 1000 1200 1400 1600
[ 16 ] [ 56 ]
[ 56 ] [ 61 ]
[ 62 ] [ 63 , 64 , 65 ]
[ 66 ] [ 67 ]
Temperature (K)
Thermalcond
uctiv
ity (W
m‐1K‐
1 )
7‐8 wt% YSZ from Figure 1 κ of Sm2Zr2O7
in lower range of YSZ
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J. Fergus. Met. Mater. Trans E 1, 118 (2014).
Ytterbium-doping
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
200 400 600 800 1000 1200 1400 1600
0 Yb0.1 Yb0.3 Yb0.5 Yb
Temperature (K)
Thermalcond
uctiv
ity (W
m‐1K‐
1 )
(Gd1‐xYbx)Zr2O7
Increasing Yb
7‐8 wt% YSZ from Figure 1
Gd2Zr2O7from Figure 7
Sm2Zr2O7from Figure 8
Doping can reduce κ
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J. Fergus. Met. Mater. Trans E 1, 118 (2014).
Thermal conductivity of mixed pyrochlores
1.4
1.6
1.8
2.0
2.2
2.4
2.6
0.0 0.2 0.4 0.6 0.8 1.0
[ 55 ] [ 66 ]
Thermalcond
uctiv
ity (W
m‐1K‐
1 )
x
(La1‐xGdx)Zr2O7
(Sm1‐xYbx)Zr2O7
Pyrochloresolid solutions have lower κ
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J. Fergus. Met. Mater. Trans E 1, 118 (2014).
Pyrochlore coating materials
• Synthesis of pyrochlore– Co-precipitation
• CMAS exposure– Melt / solidify Ca-Mg-Al-Si oxide
mixtures– Crush glass, apply to pyrochlore pellet– Expose to 1200-1400°C
• Characterization– XRD, SEM, optical microscopy
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CMAS CompositionOxide PercentageCaO 33MgO 9AlO1.5 13SiO2 45
Microstructure of Gd2Zr2O7
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Co-precipitation
Phase content of Gd2Zr2O7
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30 40 50 60 70 80 90
(511
)
(531
)
(840
)(6
62)
(800
)
(444
)(6
22)
(440
)
(331
)(400
)
(222
)
1500C 5h
1400C 10h
1400C 5h
Inte
nsity
(A.U
.)
2
Pyrochlore
Gd2Zr2O7 after CMAS at 1400°C for 5 hours
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30 40 50 60 70 80 90
****
P(511)P(331)
P(511)P(331)
PPPP
PP
P
P
PPPP
PPP
PFFFF
FFF
2Before corrosion
Non-contacted surface
CMAS contacted surface
Inte
nsity
(A.U
.)
F
* Ca2Gd8(SiO4)6O2
# Gd2Si2O7P Pyrochlore Gd2Zr2O7F Fluorite structure
Pyrochlore
Fluorite
Gd2Zr2O7 after CMAS at 1300°C for 5 hours
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30 40 50 60 70 80 90
# ## *****
P(511)P(331) PPPP
PP
P
P
PPPP
PP
P(511)P(331)P
F
FFFFF
FF
* *****
2Before corrosion
Non-contacted surface
CMAS contacted surface
Inte
nsity
(A.U
.)
*
* Ca2Gd8(SiO4)6O2
P
# Gd2Si2O7
P Pyrochlore Gd2Zr2O7F Fluorite structure
Pyrochlore
Fluorite
Gd2Zr2O7 after CMAS at 1300°C for 5 hours
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Gd2Zr2O7 after CMAS at 1300°C for 5 hours
Ca2Gd8(SiO4)6O2
Gd2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 62 - - 14 5 - 15 42 60 2 4 12 5 - 13 4
Gd silicate
Gd2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 56 - - 14 6 1 17 52 63 - 3 12 5 1 13 43 67 - 1 12 4 1 12 34 64 - 1 1 5 - 13 4
Gd silicate
Gd2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 60 1 1 1 2 27 5 42 67 - 1 1 2 23 4 33 61 - 1 2 2 25 6 4
Cubic fluorite
Gd2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 59 - - - - 17 18 52 65 - - - - 18 17 -
Pyrochlore
Gd2Zr2O7 after CMAS at 1200°C
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Concentration# Mg Al Si Ca Zr Gd1 0 0 15 7 9 142 0 0 15 6 11 203 0 0 14 6 7 124 0 0 2 2 33 55 0 0 2 3 34 76 0 0 2 2 29 5
Concentration# Mg Al Si Ca Zr Gd1 0 0 2 3 32 42 0 0 2 3 38 63 0 0 2 3 35 64 0 0 15 6 6 135 0 0 13 11 10 286 0 0 5 4 18 7
40 hours 60 hours
Gd2Zr2O7 after CMAS at 1200°C – 60 hours
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Gd+Zr
CMAS
ZrO2-Gd2O3phase diagram
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T = tetragonalF = cubic fluoriteM – monoclinicP = pyrochloreC, B, H = Gd2O3 phases
Microstructure of Sm2Zr2O7
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1μm
Figure 2. Surface morphology of Sm2Zr2O7, sintered at 1500°C for 5h.
Phase content of Sm2Zr2O7
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30 40 50 60 70 80 90
1500C 5h
1400C 15h
1400C 10h
(511
)
(311
)
(840
)(6
62)
(800
)
(444
)(6
22)
(440
)
(331
)(440
)
Inte
nsity
(A.U
.)
2
(222
)
1400C 5h
Sm2Zr2O7 after CMAS at 1400°C for 5 hours
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30 40 50 60 70 80 90
****
P(511)P(331)
P(511)P(331)
PPPP
PP
P
P
PPP P
PPP
P
FFFFFFF
2
Before Corrosion
Non-contactedsurface
CMAS contacted surface
* Ca2Sm8(SiO4)6O2
P Pyrochlore Sm2Zr2O7F Fluorite Sm2Zr2O7
Inte
nsity
(A.U
.)
F
*
Sm2Zr2O7 after CMAS at 1300°C for 5 hours
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30 40 50 60 70 80 90
*****
P(331)
P(511)
P(511)
PPPP
PP
P
P
PPPP
PP
P(331)
P
P
FFFFFF
F
F
Inte
nsity
(A.U
.)
2
Before corrosion
Non-contacted surface
CMAS contacted surface
* Ca2Sm8(SiO4)6O2
P Pyrochlore Sm2Zr2O7F Fluorite Sm2Zr2O7
*
Sm2Zr2O7 after CMAS at 1300°C for 5 hours
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10μm
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Sm2Zr2O7 after CMAS at 1300°C for 5 hours
Sm2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 47 1 8 20 11 2 8 32 60 3 10 18 7 1 1 23 58 1 5 16 9 1 7 34 53 6 5 17 18 - - 25 54 4 7 17 13 - 1 26 55 3 10 19 10 1 1 2
1,3: Bright spotsSm silicate
Sm2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 62 - 1 1 2 27 4 32 66 - - 1 2 25 3 33 58 2 5 7 10 13 3 34 65 1 2 3 5 18 4 2
Cubic fluorite
Sm2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 47 - - 10 6 6 23 92 44 - - 2 4 38 7 53 51 - - 7 7 15 15 54 54 - - 2 3 31 6 45 40 - - 8 7 12 26 96 53 - 1 4 4 26 7 5
1,3,5: Sm silicate2,4,6: Cubic fluorite
Sm2Zr2O7 after CMAS at 1300°C for 15 minutes + 1200°C for 30 hours
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Concentration
# O Mg Al Si Ca Zr Gd Au1 67 - 1 - - 18 12 22 72 - - 1 - 17 7 33 68 - - - - 19 13 -4 65 - - - - 18 15 35 66 - - 1 - 18 12 3
Pyrochlore
Sm2Zr2O7 after CMAS at 1200°C – 60 hours
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Concentration# Mg Al Si Ca Zr Gd1 0 0 15 6 7 132 0 0 16 6 5 143 0 0 15 6 6 124 0 0 0 3 33 35 0 0 1 2 33 36 0 0 1 3 37 4
Sm2Zr2O7 after CMAS at 1200°C – 60 hours
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CMAS
Sm + Zr
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T = tetragonalF = cubic fluoriteM – monoclinicPyr = pyrochloreC, B, H = Sm2O3 phases
ZrO2-Sm2O3phase diagram
(Gd,Sm)2Zr2O7 after CMAS at 1200°C for 60 hours
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(Gd0.8Sm0.2)2Zr2O7 (Gd0.6Sm0.4)2Zr2O7
Concentration# Mg Al Si Ca Zr Sm Gd1 0 0 14 5 5 10 02 0 0 19 7 6 17 03 0 0 17 6 8 14 04 0 0 17 6 8 14 15 0 0 1 3 41 5 06 0 0 3 3 46 6 07 0 0 2 3 45 6 0
Concentration# Mg Al Si Ca Zr Sm Gd1 0 0 17 7 6 6 92 0 0 15 10 9 10 143 0 0 13 5 4 4 64 0 0 1 3 35 1 35 0 0 1 2 36 2 36 0 0 1 3 39 2 4
Conclusions• Coatings
– Ni flash coating needed to obtain quality Re coating– Only 2 out of 20 Ir coatings on Re-coatings round
samples were successful– No Ir coatings on rectangular samples were
successful• EBC materials
– Reaction of Gd2Zr2O7, Sm2Zr2O7 and (Gd,Sm)2Zr2O7with CMAS evaluated
• Pyrochlore dissolves in CMAS• Reprecipitates as lanthanide silicate and cubic fluorite phase
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