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