Electrophoretic Deposition Barrier Coating for Gas Turbine EBC
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Solution Overview
Problem
Current environmental barrier coatings (EBCs) for ceramic components in gas turbine engines are susceptible to damage from molten dust and subsequent gas erosion, particle erosion, and particle impact, leading to coating delamination and spalling.
Innovation Solution
An electrophoretic deposition (ED) process is used to form a coating on a substrate using a slurry containing EBC material particles, a cationic polyelectrolyte, polymeric binder particles, and a solvent, which inhibits cracking and ensures the coating is hermetic to high temperature steam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EBC materials (BSAS, rare earth silicates) are used, then the coating provides steam resistance and protects the CMC substrate, but the coating is susceptible to molten dust attack, infiltration, and subsequent erosion leading to delamination and spalling
Solution Approach 1:
The patent uses a composite coating system consisting of multiple layers with different materials: a first layer of BSAS or rare earth silicate for steam resistance, and a second layer of alumina or silica for molten dust resistance. This composite structure allows each material to perform its specialized function, resolving the contradiction between steam protection and molten dust resistance.
Solution Approach 2:
The coating is divided into multiple functional layers: a base layer for steam barrier protection and an outer layer for molten dust resistance. This segmentation allows each layer to be optimized for its specific function, preventing molten dust infiltration while maintaining steam barrier integrity.
2Reliability
If the coating is made dense to prevent steam penetration, then the hermetic seal is improved, but the coating becomes more susceptible to crack propagation and delamination under thermal and mechanical stress
Solution Approach 1:
The coating system provides different local properties: the inner layer is dense and hermetic for steam protection, while the outer layer has enhanced mechanical strength and crack resistance. Each region of the coating system has optimized properties suited to its specific functional requirements.
Solution Approach 2:
The composite structure combines materials with complementary properties: BSAS or rare earth silicates provide hermetic sealing, while alumina or silica layers provide mechanical strength and crack resistance. The interface between layers is designed to accommodate thermal expansion differences while maintaining overall integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The ED process results in a coating that is less susceptible to molten dust attack and subsequent erosion, providing improved resistance to gas erosion, particle erosion, and particle impact, thus enhancing the durability and integrity of the coating.
Implementation Method 1
electrophoretic deposition of a slurry
Data Source
AI summary
Methods are provided for forming a coating on a surface of a substrate. The method may include: applying a negative charge to the surface of the substrate; electrophoretically depositing a slurry layer onto the surface of the substrate; and densifying the slurry layer on the surface of the substrate at a sintering temperature to form a sintered layer of the coating. The slurry layer may include a plurality of EBC material particles, a cationic polyelectrolyte, a plurality of polymeric binder particles, and a solvent. The plurality of EBC material particles may comprise barium strontium aluminosilicate (BSAS), mullite, silicon, rare earth compounds, or combinations thereof.