Rare Earth Silicate Abradable Coating for Gas Turbine Seals
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Solution Overview
Problem
High-temperature mechanical systems, such as gas-turbine engines, face challenges in maintaining efficiency and reducing leakage due to the gap between turbine blades and surrounding components, which existing coatings fail to address effectively.
Innovation Solution
An abradable coating composed of rare earth silicate, potentially with alternating layers of stabilized zirconia or hafnia, is applied over a substrate or existing coatings to create a seal by wearing down to fit the blade path, reducing gas leakage and enhancing engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermal barrier coating (TBC) is applied to reduce surface temperatures, then the substrate temperature is reduced, but the coating does not address gas leakage between blade and track
Solution Approach 1:
The coating system is segmented into multiple functional layers: a thermal barrier coating (TBC) layer for temperature reduction and an abradable coating layer for sealing. This segmentation allows each layer to independently perform its specific function without interfering with the other, thereby simultaneously addressing both temperature control and gas leakage prevention
Solution Approach 2:
The abradable coating serves multiple functions: it provides a sealing interface to prevent gas leakage, maintains thermal barrier properties, and allows for controlled wear to accommodate blade thermal expansion. By integrating these functions into a single coating system, the invention eliminates gas leakage while preserving temperature protection
2Reliability
If an environmental barrier coating (EBC) is applied to protect from water vapor attack, then substrate protection is improved, but gas leakage between blade and track remains unaddressed
Solution Approach 1:
The coating system is segmented into distinct functional layers: an environmental barrier coating (EBC) layer for substrate protection against water vapor and corrosion, and an abradable coating layer for sealing. This segmentation enables each layer to independently perform its specific function, simultaneously achieving substrate protection and gas leakage prevention
Solution Approach 2:
The abradable coating acts as an intermediary layer between the protected substrate and the blade, providing a compliant sealing surface that accommodates thermal expansion while preventing gas leakage. This intermediary layer resolves the conflict between maintaining substrate protection and eliminating gas paths
3Loss of energy
If the gap between blade and track is reduced to eliminate leakage, then efficiency is improved, but thermal expansion accommodation becomes difficult
Solution Approach 1:
The abradable coating introduces dynamic adaptability to the sealing interface. As the blade undergoes thermal expansion, the coating dynamically adjusts by allowing controlled blade contact and wear, maintaining the seal without constraining thermal movement. This dynamic behavior accommodates thermal expansion while preventing gas leakage
Solution Approach 2:
The abradable coating provides self-adjusting sealing through controlled wear. When the blade expands thermally, the coating automatically accommodates the movement through material removal, maintaining intimate contact and sealing without requiring external adjustment mechanisms. The coating serves itself by using wear as a compliance mechanism
4Loss of energy
If a rigid seal is used to eliminate gas leakage, then sealing effectiveness is improved, but damage to blade or track occurs due to lack of compliance
Solution Approach 1:
The abradable coating functions as a flexible, compliant layer that can deform and wear without transmitting damaging forces to the blade or track. This flexible film provides effective sealing while accommodating thermal expansion through controlled material removal, preventing damage to critical components
Solution Approach 2:
The abradable coating is designed as a sacrificial, consumable layer that gradually wears away to accommodate blade expansion. This disposable coating layer protects the expensive blade and track from damage by absorbing wear through controlled material loss, maintaining sealing effectiveness throughout the component lifecycle
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 abradable coating effectively reduces gas leakage by forming a precise fit between the blade and the coating, potentially increasing gas turbine engine efficiency by up to 5% and maintaining performance across varying temperatures.
Implementation Method 1
the tip of the turbine blade intentionally contacts the abradable coating and wears away a portion of the coating to form a groove in the abradable coating
Implementation Method 2
The thermal barrier coating may include a thermally insulative ceramic topcoat
Data Source
AI summary
An abradable coating may include a rare earth silicate. The abradable coating may be deposited over a substrate, an environmental barrier coating, or a thermal barrier coating. The abradable coating may be deposited on a gas turbine blade track or a gas turbine blade shroud to form a seal between the gas turbine blade track or gas turbine blade shroud and a gas turbine blade. The abradable coating may also include a plurality of layers, such as alternating first and second layers including, respectively, a rare earth silicate and stabilized zirconia or stabilized hafnia.