CMAS Resistant Coating for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engine components face significant challenges due to the infiltration and dissolution of Calcium Magnesium Alumino-Silicate (CMAS) deposits, which lead to coating recession and spallation, especially at high operating temperatures and in environments with high CMAS concentrations.
Innovation Solution
A multi-cation rare-earth monosilicate composition is integrated into the environmental barrier coating (EBC) system, forming a CMAS-resistant layer that reacts with CMAS to produce stable apatite phases, acting as a barrier to reduce infiltration and dissolution, and is tailored to match the coefficient of thermal expansion of the underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional EBC layer is used to protect the substrate from environmental species, then the substrate is protected from oxygen and water vapor, but the EBC layer is vulnerable to CMAS infiltration and dissolution at high temperatures
Solution Approach 1:
The patent applies composite materials by creating a CMAS resistant layer composed of multiple rare-earth metal cations (at least two different RE metals) in a monosilicate structure. This composite composition provides enhanced CMAS resistance compared to single-metal EBC layers, while maintaining the environmental barrier protection function. The multi-cation composition forms a more stable reaction product with CMAS, reducing infiltration and dissolution.
Solution Approach 2:
The patent changes the compositional parameters of the EBC layer by incorporating multiple rare-earth metal cations with specific atomic ratios. The composition is defined as RE1(1-x)RE2xSiO5 where x ranges from 0.1 to 0.9, allowing optimization of CMAS resistance while maintaining thermal expansion compatibility. This parameter adjustment transforms the conventional single-metal EBC into a multi-metal composite with superior high-temperature stability.
2Object-affected harmful factors
If the EBC layer composition is modified to improve CMAS resistance, then CMAS infiltration is reduced, but the coefficient of thermal expansion may no longer match the underlying substrate and EBC layers
Solution Approach 1:
The patent applies local quality by selectively choosing rare-earth metal cations and their ratios to achieve specific local properties in the CMAS resistant layer. The composition RE1(1-x)RE2xSiO5 allows tailoring of both CMAS resistance and thermal expansion coefficient at this specific location (the outer EBC layer), while maintaining compatibility with underlying layers. Different RE metal combinations can be used to optimize for specific operating conditions.
3Reliability
If a multi-cation RE monosilicate composition is used to form stable apatite phases, then CMAS resistance is enhanced, but the coating system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the EBC system into distinct functional layers: a conventional EBC layer for environmental protection and a separate CMAS resistant layer with multi-cation composition for CMAS protection. This segmentation allows each layer to be optimized for its specific function without compromising the other, managing complexity through functional decomposition.
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 CMAS-resistant layer effectively prevents coating degradation by forming stable apatite phases over a wide temperature range, enhancing the durability and thermal protection of the EBC system, thereby improving the operational life of gas turbine engine components.
Implementation Method 1
the RE monosilicate composition is configured to react with CMAS to form a reaction product including a RE apatite phase
Implementation Method 2
the CMAS resistant layer may serve as a barrier that reduces infiltration of the CMAS and/or reduces dissolution of the CMAS resistant layer
Implementation Method 3
the RE apatite phase formed from the reaction with CMAS may be stable over the operating temperature range of the article (e.g., from room temperature to about 1500 degrees Celsius)
Implementation Method 4
the RE metal cations may be selected such that the CMAS resistant layer exhibits other beneficial properties such as a coefficient of thermal expansion (CTE) that is similar to that of the CTE of the underlying EBC layer
Data Source
AI summary
An article may include a substrate and a coating system on the substrate. The coating system may include an environmental barrier coating (EBC) layer and a CMAS resistant layer on the EBC layer (e.g., as the top coat of the system). The CMAS layer includes a rare-earth (RE) monosilicate composition including a plurality of RE metal cations, wherein RE monosilicate composition is configured to react with CMAS to form a reaction product including a RE apatite phase with a RE2O3·SiO2 composition, wherein the RE of the RE2O3·SiO2 composition includes at least one of the plurality of RE metal cations of the RE monosilicate.