Breathable Environmental Barrier Coating for Gas Turbines
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Solution Overview
Problem
Current environmental barrier coatings (EBCs) for ceramic components in high-temperature gas turbine engines cannot prevent oxygen penetration, leading to substrate oxidation and blistering due to the inability to escape carbonaceous or nitrogen-based gases, and the use of a silicon bond coat limits the operational temperature due to its low melting point.
Innovation Solution
A breathable silicon-containing glass phase is integrated into the barrier layer, allowing for the diffusion of carbonaceous and nitrogen-based gases while maintaining a hermetic seal against water vapor, eliminating the need for a silicon bond coat and enabling higher operational temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dense EBC is used to seal out water vapor, then recession is prevented, but oxygen penetration occurs causing substrate oxidation and blistering
Solution Approach 1:
The patent applies a porous or breathable barrier layer that allows controlled diffusion of oxygen and gaseous by-products while maintaining a dense enough structure to prevent water vapor penetration. This resolves the contradiction by enabling selective permeability - the layer is porous enough to allow gas diffusion but dense enough to block water vapor, preventing both recession and substrate oxidation simultaneously.
Solution Approach 2:
The patent uses composite barrier layer compositions combining multiple materials with complementary properties - such as rare earth silicates, mullite, and other ceramic materials - to achieve both water vapor impermeability and controlled oxygen/gas permeability. The composite structure allows each material to contribute its strengths, creating a barrier layer that prevents recession while allowing safe gas diffusion.
2Reliability
If a silicon bond coat is used to prevent blistering, then gas escape is enabled, but operational temperature is limited due to low melting point
Solution Approach 1:
The patent extracts or eliminates the silicon bond coat layer from the coating system. By removing this low-temperature-limiting layer, the system can operate at higher temperatures. The breathable barrier layer directly replaces the bond coat function, allowing gas diffusion without requiring a separate silicon-based intermediate layer, thus eliminating the melting point constraint.
Solution Approach 2:
The patent changes the material parameters of the barrier layer to achieve both gas permeability and high temperature stability. By selecting ceramic materials with appropriate pore structures and thermal properties, the barrier layer achieves the gas escape function previously requiring silicon bond coat, but with temperature stability exceeding 2500°F (1371°C).
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 breathable silicon-containing glass phase prevents blistering and delamination, allowing EBCs to operate at temperatures exceeding 2500°F (1371°C) without a bond coat, providing a stable and efficient thermal barrier.
Implementation Method 1
A breathable silicon-containing glass phase is integrated into the barrier layer, allowing for the diffusion of carbonaceous and nitrogen-based gases
Implementation Method 2
maintaining a hermetic seal against water vapor
Implementation Method 3
thermal barrier coatings (TBCs) can be utilized to insulate the components and can sustain an appreciable temperature difference between the load-bearing alloys and the coating surface
Data Source
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AI summary
A coated substrate is provided that includes an environmental barrier coating on (e.g., directly on) a surface of a substrate (e.g., a ceramic matrix composite). The environmental barrier coating can include a barrier layer having a refractory material phase and a silicon-containing glass phase. The silicon-containing glass phase may be a continuous phase within the barrier layer (e.g., a breathable grain boundary of the barrier layer), or may be a plurality of discontinuous layers dispersed throughout the refractory material phase. The refractory material phase can include a rare earth silicate material having a rare earth component at a first atomic percent, while the silicon-containing glass phase comprises the rare earth component at a second atomic percent that is less than the first atomic percent. Methods are also provided for forming a barrier layer on a substrate.