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Derek D. Hass
"Directed Vapor Deposition of Thermal Barrier Coatings"
Ph.D. Dissertation, University of Virginia, 2000.
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Abstract
Acknowledgements
List of Symbols
List of Figures
List of Tables
I. Introduction
- Turbine Engine Development
- TBC Thermal Protection
- Goals of the Dissertation
II. Thermal Barrier Coatings
- Overview
- TBC Systems
- Materials Selection
- Property Profiles
- TBC Pore Morphology
- Advanced Processing Approaches for TBCS
- Summary
III. Electron Beam Directed Vapor Deposition
- Overview
- EB-DVD Concept
- Carrier Gas Speed
- Mean Free Path
- Process Condition Window
- Summary
IV. DVD Modifications for YSZ Deposition
- Oxygen Introduction into the Carrier Gas Jet
- Evaporation
- Substrate Manipulation
- Substrate Heating Approaches
- Available Processing Regime
V. Experimental Methodology
- Substrate Material
- Nickel superalloy base
- Nickel aluminide bond coat
- Surface roughness on the substrate
- Source Material
- Carrier Gas
- YSZ Deposition
- Coating Characterization
- Scanning electron microscope
- X-ray diffraction
- Characterization of the Pore Morphology
- Thermal Conductivity Measurement
- Density Measurement
VI. Morphology of YSZ Deposited Using DVD
- Overview
- Experimental Setup
- Pore Morphology
- Coating Morphologies
- Phases and Texture
- Discussion
- Summary
VII. Simulation of Vapor Transport
- Overview
- Vapor Transport Modeling
- Nozzle Expansion
- Model Set-Up
- Helium Expansion
- Gas jet interactions with flat substrate
- Helium-oxygen gas jet/substrate interactions
- Summary of carrier gas nozzle expansion simulations
- Chamber Geometry Effects
- Model Set-up
- Crucible/carrier gas interactions
- Angle of Incidence Determination
- Zirconia VHS parameters
- Simulation approach
VIII. Chamber Pressure Effects
- Overview
- Experimental Setup
- Constant pressure ratio
- Constant gas flow rate
- Coating Morphology
- Constant pressure ratio experiments
- Constant gas flow rate experiments
- Texture
- Density
- Thermal Conductivity
- DSMC Results
- Constant pressure ratio
- Constant gas flow rate
- Summary
- Constant pressure ratio
- Constant gas flow rate
- Coating property effects
- DSMC results
IX. Pressure Ratio Effects
- Overview
- Experimental Setup
- Coating Morphology
- Texture
- Density
- DSMC Results
- Gas Jet Flow
- Angle of Incidence
- Summary
X. Substrate Temperature Effects
- Overview
- Experimental Setup
- Coating Morphology
- Texture
- Density
- Summary
XI. Evaporation and Deposition Rate Effects
- Overview
- Experimental Setup
- Coating Morphology
- Texture
- Density
- DSMC Simulation
- Gas jet flow
- Angle of Incidence
- Summary
XII. Pore Engineering
- Experimental Conditions
- Coating Morphology
- Thermal Conductivity
- Discussion
- Effect of processing induced porosity on thermal conductivity of TBC layers
- Tailoring approaches
- Optimization for use at elevated temperature
- Summary
XIII. Coating Growth Simulations
- Kinetic Monte Carlo (KMC)
- The Model
- KMC Simulations - Type I Pore Formation
- Angle of Incidence Distribution Effects
- Effect of distribution width
- Effect of peak position
- Roughness Geometry Effects
- Asperity height
- Asperity spacing
- Single asperitites
- Flux Shadowing Mechanisms
- Substrate Temperature Effects
- Deposition Rate Effects
- Summary
XIV. Discussion
- Overview
- Factors Effecting Coating Morphology
- Surface roughness
- Angle of incidence distribution
- Surface Diffusion
- Cluster formation in the vapor phase
- Effects of process conditions on coating morphology
- Pore morphology
- Type I pore inclination angle
- Type I pore spacing
- Type I pore width
- Coating Properties
- Implications for Thermal Barrier Coatings
- DVD TBC processing regime
Conclusions
References
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