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Department of Materials
Reacting CMAS with Yttrium Disilicate Environmental Barrier Coating
Mentor: William Summers
w Professor Frank Zok
Melissa Morales w
Chemical Engineering w
UC Santa Barbara
Silicon carbide ceramic matrix composites (SiC CMCs) likely to replace nickel alloys
Boeing 727-100 aircraft
http://www.pw.utc.com/JT8D_EnginePratt & Whitney JT8D Engine
http://www.pw.utc.com/JT8D_Engine
2
1973-1982
1986-1996
2000
Firing Temperature (oC)
900 1000 1100 1200 1300 1400 1500 160040
45
50
55
60
65
Combined CycleEfficiency (%)
3.2% / 100oC
Raising firing temperature improves engine efficiency
Adapted from GE Power Systems GER-41943
Images courtesy GE Aviation
Silicon carbide ceramic matrix composites (SiC CMCs) likely to replace nickel alloys
4
1975 1985 1995 2005 2015 2025
Super alloys
SiC/SiCCMC
Year
Temperature (oC)
Adapted from Richards, Wadley 2014
Silicon carbide ceramic matrix composites (SiC CMCs) likely to replace nickel alloys
1965
700
900
1100
1300
1500
1700
1900
5
Without Environmental Barrier Coating
SiC CMC
O2
6
Without Environmental Barrier Coating
SiC CMCSiO2
O2
7
Without Environmental Barrier Coating
SiC CMCSiO2
H2O
8
Without Environmental Barrier Coating
SiC CMCSiO2
H2O Si(OH)4
9
Without Environmental Barrier Coating
SiC CMC
10
Without Environmental Barrier Coating
SiC CMCSiO2
H2O Si(OH)4
11
Without Environmental Barrier Coating
SiC CMCSiO2
H2O Si(OH)4
12
Without Environmental Barrier Coating
SiC CMCSiO2
H2O Si(OH)4
13
EBC
With Environmental Barrier Coating
SiC CMC14
EBC
With Environmental Barrier Coating
H2O
SiC CMC15
O2
EBC
CMAS
With Environmental Barrier Coating
SiO2
• CMAS: Calcium-Magnesium-Alumina-Silicate• Siliceous materials, desert sand to volcanic ash
SiC CMC16
EBC
CMAS
With Environmental Barrier Coating
apatite
SiC CMCSiO2
17
CMAS
(CaO)31%(MgO)9%(FeO1.5)5%(AlO1.5)12%(SiO2)43% at 1400oC – 4 hours
YDS EBC
Apatite
100 μm
Apatite byproduct causes cracks to form in environmental barrier coating layer
18
CMAS
YDS EBC
Apatite
100 μm
Apatite byproduct causes cracks to form in environmental barrier coating layer
How can we prevent or mitigate the reaction between the EBC and CMAS?
19
0.5 1.0 1.5 2.0
Predicted Equilibria
Mol of Yttrium Disilicate EBC Consumed
0.8
0.6
0.4
0.2
0.0
Calcia to Silica Mol Ratio
(CaO)31%(MgO)9%(FeO1.5)5%(AlO1.5)12%(SiO2)43%
(CaO)20%(MgO)5%(FeO1.5)5% (AlO1.5)10%(SiO2)60%
(CaO)10%(MgO)5%(FeO1.5)5% (AlO1.5)5%(SiO2)70%
20
David Poerschke
Prepare and Grind Powders
21
Prepare and Grind Powders
22
Prepare and Grind Powders
23
Press Powders Into Pellets
24
React Powders in Furnace (1300oC)
25
Prepare for Microscope
26
3000X Test 1 C31%S43% & 0.333 mol YDS
Pore
CMAS
Apatite
27
3000X Test 5 C31%S43% & 2.0 mol YDS
Anorthite
Apatite
CMAS
28
Residual Yttrium Disilicate
3000X Test 5 C31%S43% & 2.0 mol YDS
29
3000X Test 3 C10%S70% & 0.333 mol YDS
CMAS
Anorthite
30
3000X Test 4 C31%S43% & 1.0 mol YDS
CMAS
Anorthite
Apatite
31
CaO MgO FeO1.5 AlO1.5 SiO2 YO1.5
Expected 8% 4% 4% 8% 65% 12%
Measured 5% 2% 3% 37% 45% 9%
Expected- Al
8% 4% 4% 70% 14%
Measured- Al
8% 3% 4% 71% 14%
Test 3: Overall vs. Expected
32
CaO MgO FeO1.5 AlO1.5 SiO2 YO1.5
Expected 8% 4% 4% 8% 65% 12%
Measured 5% 2% 3% 37% 45% 9%
Expected- Al
8% 4% 4% 70% 14%
Measured- Al
8% 3% 4% 71% 14%
Test 3: Overall vs. Expected
33
CaO MgO FeO1.5 AlO1.5 SiO2 YO1.5
Expected 8% 4% 4% 8% 65% 12%
Measured 5% 2% 3% 37% 45% 9%
Expected- Al
8% 4% 4% 70% 14%
Measured- Al
8% 3% 4% 71% 14%
Test 3: Overall vs. Expected
34
Anorthite
Future Recession Experiments
35
Future Recession Experiments
36
Future Recession Experiments
200 μm
200 μm
200 μm
(CaO)31%[…](SiO2)43% at 1400oC - 4 hours
(CaO)20%[…](SiO2)60% at 1400oC - 4 hours
(CaO)10%[…](SiO2)70% at 1400oC - 4 hours 37
AcknowledgementsWilliam Summers
David Poerschke
Frank W. Zok
Stephanie Mendes
Kelly Ibsen
Chris Siefe
Megan Wakefield