Multi-Phase Abradable Coating for Turbine Tip Clearance
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Solution Overview
Problem
Current abradable coatings for ceramic matrix composites (CMC) in turbine engines are prone to depletion during initial engine burn, leading to inefficient tip clearance and potential damage to the blade, necessitating an improved coating that balances wearability and durability.
Innovation Solution
A multi-phase abradable coating system comprising a ceramic matrix and a dislocator phase, where the dislocator phase transforms into micro-cracked ZrO2 upon exposure to a combustion gas atmosphere, allowing the coating to be abraded while maintaining durability, combined with a top coat and bond coat for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an abradable coating is deposited on top of the EBC to protect it from blade rub, then the EBC is protected from damage, but the coating is depleted by the initial engine burn, leading to inefficient tip clearance
Solution Approach 1:
The coating system is segmented into multiple functional layers: a bond coat for adhesion to the CMC substrate, an intermediate layer containing the abradable phase, and a top coat providing environmental barrier protection. This segmentation allows each layer to perform its specific function optimally while working together to resolve the contradiction between protection and wearability.
Solution Approach 2:
The invention uses a composite coating system combining different materials with complementary properties: the bond coat provides strong adhesion, the intermediate layer contains abradable phases (such as alumina or silica) that wear away to create tip clearance, and the top coat provides environmental barrier protection. This composite structure resolves the contradiction by integrating materials that simultaneously provide protection and controlled wear.
2Strength
If the abradable coating is made more wear-resistant to maintain durability, then the coating protects the substrate better, but the blade cannot wear away the coating to minimize the gap between blade and shroud
Solution Approach 1:
The coating system exhibits local quality differentiation where the intermediate layer is specifically designed with abradable phases that are softer and more wear-resistant than the top coat, allowing localized wear in the intermediate layer while the top coat maintains its protective function. This local differentiation enables the coating to wear where needed (intermediate layer) while maintaining durability where needed (top coat and bond coat).
Solution Approach 2:
The coating system utilizes parameter changes in material properties at different layers: the bond coat has high hardness and strength for substrate protection, the intermediate layer has controlled wear properties with abradable phases, and the top coat has optimized environmental barrier properties. These parameter changes across layers allow the system to simultaneously achieve durability and wearability.
3Ease of manufacture
If a single-phase coating is used for simplicity, then the manufacturing process is easier, but the coating cannot simultaneously provide abradability and environmental barrier protection
Solution Approach 1:
The coating system is segmented into multiple functional layers deposited in sequence: first the bond coat is applied to ensure adhesion to the CMC substrate, then the intermediate layer with abradable phases is deposited, and finally the top coat providing environmental barrier protection is applied. This segmented approach, while adding manufacturing steps, enables the simultaneous achievement of abradability and environmental barrier protection that a single-phase coating cannot provide.
Solution Approach 2:
The invention employs a composite coating system where each layer is composed of materials specifically selected for its function: the bond coat uses materials with high adhesion to CMC, the intermediate layer contains abradable phases such as alumina or silica particles, and the top coat uses environmental barrier materials. This composite material approach enables dual functionality that outweighs the increased manufacturing complexity.
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 multi-phase abradable coating effectively reduces tip clearance without damaging the blade, maintaining durability and protecting the underlying substrate, thereby enhancing turbine performance and efficiency.
Implementation Method 1
the dislocator phase transforms into micro-cracked ZrO2 upon exposure to a combustion gas atmosphere
Implementation Method 2
the dislocator phase transforms into micro-cracked ZrO2
Implementation Method 3
an abradable coating which can be worn away by the blade to minimize the gap between the blade and shroud
Implementation Method 4
a multi-phase abradable coating system comprising a ceramic matrix and a dislocator phase
Data Source
AI summary
Disclosed is a multi-phase abradable coating including a ceramic matrix and a dislocator phase.