Rare Earth Silicate EBCs for Hermetic Gas Turbine CMC Protection
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Solution Overview
Problem
Existing environmental barrier coatings (EBCs) for gas turbine engine components, particularly those made of ceramic matrix composites (CMCs), are porous and not hermetic, leading to volatilization of the ceramic matrix and degradation under harsh engine conditions, necessitating additional glassy layers that complicate the coating process.
Innovation Solution
A plasma spray process is used to apply a rare earth silicate-based hermetic layer adjacent to a silicon bondcoat, eliminating the need for glassy layers, with a sintering aid diffusing to form a high-density hermetic and non-hermetic silicate layer, providing protection against gaseous species while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional porous EBCs are applied to CMC components, then the coating process is simplified, but the hermeticity deteriorates leading to volatilization and degradation
Solution Approach 1:
The patent changes the chemical composition parameters of the EBC by incorporating rare earth silicates (such as yttrium silicate, ytterbium silicate) with specific molecular structures that inherently provide hermetic properties. This compositional parameter change enables the coating to achieve both hermeticity and durability without requiring complex multi-layer structures or additional glassy layers, thus resolving the contradiction between manufacturing simplicity and hermeticity.
2Reliability
If glassy layers are added to improve hermeticity, then the protection against gaseous species improves, but the device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for separate glassy layers by incorporating hermetic functionality directly into the rare earth silicate-based EBC composition. The rare earth silicate materials inherently provide both the barrier properties against gaseous species and the hermetic seal, allowing the removal of additional protective layers and simplifying the overall coating structure while maintaining superior protection.
3Strength
If high temperature superalloys are used for engine components, then the strength and temperature resistance improve, but the weight increases and service exposure requirements increase
Solution Approach 1:
The patent utilizes ceramic matrix composite (CMC) materials composed of refractory ceramic fibers reinforced with a ceramic matrix, coated with rare earth silicate-based EBC. This composite structure combines the lightweight advantages of ceramics with the protective benefits of the EBC, achieving superior strength and temperature resistance while maintaining lower weight compared to traditional high temperature superalloys. The composite nature of the CMC plus EBC system enables extended service exposure in harsh environments.
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 rare earth silicate-based EBC enhances the hermeticity and durability of CMC components, preventing volatilization and spallation, while maintaining lightweight properties and reducing complexity in the coating process.
Implementation Method 1
A plasma spray process is used to apply a rare earth silicate-based hermetic layer adjacent to a silicon bondcoat
Implementation Method 2
with a sintering aid diffusing to form a high-density hermetic and non-hermetic silicate layer
Data Source
AI summary
Environmental barrier coatings including a bondcoat layer including silicon and a rare earth silicate-based hermetic layer and rare earth silicate-based non-hermetic layer are provided. The rare earth silicate-based hermetic layer is deposited on the bondcoat via a thermal spray process and has an elastic modulus ranging from 100 GPa to 180 GPa. The at least one rare earth silicate-based non-hermetic layer is deposited on the rare earth silicate-based hermetic layer and has an elastic modulus ranging from 50 GPa to 100 GPa. Coated gas turbine engine components and methods for coating gas turbine engine components are also provided.