Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ...

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Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004
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Page 1: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Bradley AllisonAdvisor: Prof. Rodney Trice

Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings

REU Presentation

August 5, 2004

Page 2: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

What are TBCs?

• Ceramic Coating • Most commonly used in the gas turbine engines• Yttria Stabilized Zirconia (YSZ)

• ZrO2 - 7 wt% Y2O3

Page 3: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

What makes TBCs Useful?• Improves fuel efficiency

– Allows for higher continuous service temperature – Low Thermal conductivity ( ~ 1 W/mK )

• Improves engine reliability – Increases lifetime of parts– Prevent corrosion

Page 4: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Processing• Plasma spray• Lamella formation

Page 5: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Lamella Formation

http://www.gordonengland.co.uk/tsc.htm

Page 6: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Research Investigation

• Varying starting powder will affect lamella microstructure

• 3 powder sizes separated from a single YSZ batch– 18-26 µm– 37-52 µm– 74-105 µm

Page 7: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Experimental Procedure• Sample Preparation

– Sprayed onto cylindrical and flat Copper substrates• Archimedes Density

– Total porosity is calculated from suspended, saturated, and dry mass

– Measurements taken in as-sprayed condition and after heat treatments of 5 hours and 50 hours at 1400°C

• Dilatometer– Quantifies sintering of coatings as heat treated for 5 hours at

1400°C• SEM

– Use SEM micrographs to quantify lamella thickness• XRD

– Quantify phases present at each step during heat treatment– Based on intensity of t-ZrO2 and c-ZrO2 peaks

Page 8: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Archimedes Density• Uniform decrease in

porosity• Large particle

coatings displayed most porosity before and after heat treatment

Page 9: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Dilatometer

• Medium powder exhibited most shrinkage

• Driving force for densification

Page 10: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

SEM

Small

Medium Large

Page 11: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

SEM

Measured Lamella Thickness (µm)

195-8 Small 1.34 ± 0.39

195-7 Medium 2.01± 0.72

195-6 Large 2.95 ± 0.97

Page 12: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

X-ray Diffraction

•Super Saturated Solid Solution of Y2O3 in ZrO2

•As Y2O3 diffuses out of ZrO2 , c-ZrO2 is formed

Page 13: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

X-ray Diffraction

Page 14: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Future Research to be Explored

• Study phase transformation during heat treatment with respect to varying lamella size

• Study thermal conductivity of coatings throughout heat treatment with respect to varying lamella size

Page 15: Bradley Allison Advisor: Prof. Rodney Trice Effects of Starting Powder Size on Sintering of YSZ Thermal Barrier Coatings REU Presentation August 5, 2004.

Acknowledgments

• Prof. Trice and Prof. Kvam• Kei Yamamoto and Jan Eberle• Chris Petorak and Ben Iverson• REU and Surf Students