Cerium Oxide Layer in Environmental Barrier Coatings
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Solution Overview
Problem
Current environmental barrier coatings (EBCs) for silicon materials in gas turbine engines are susceptible to silicate glass formation when exposed to sulfate salt deposits at high temperatures, leading to corrosion and increased recession rates, which compromises their protective effectiveness.
Innovation Solution
A multi-layer EBC system comprising a bond layer of silicon, a first layer of mullite, a second layer of barium strontium aluminosilicate, and a third layer of cerium oxide is applied to the silicon substrate, where the cerium oxide layer reduces silicate glass formation upon exposure to corrosive sulfates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-layer EBCs are used to prevent water vapor recession of CMC substrates, then protection against environmental corrosion is improved, but susceptibility to silicate glass formation increases when exposed to sulfate salt deposits at high temperatures
Solution Approach 1:
The EBC is divided into multiple functional layers with distinct compositions and purposes. The bond layer (silicon material) provides substrate attachment and initial protection, the mullite layer (first layer) offers structural stability and intermediate protection, the BSAS layer (second layer) provides environmental barrier properties, and the cerium oxide layer (third layer) specifically prevents silicate glass formation by reacting with sulfates. This segmentation allows each layer to address specific degradation mechanisms without compromising the others.
Solution Approach 2:
The invention uses a composite multi-layer structure combining different materials (silicon, mullite, BSAS, cerium oxide) that work synergistically. The cerium oxide layer acts as a protective composite that specifically addresses the silicate glass formation issue while the underlying layers provide their respective protection functions, creating a comprehensive defense system against multiple degradation pathways.
2Use of energy by moving object
If operating temperatures are increased to improve gas turbine engine efficiency, then energy efficiency is improved, but high temperature durability of components must increase
Solution Approach 1:
The invention modifies the chemical composition parameters of the EBC by incorporating cerium oxide in the third layer. This compositional change enables the coating to maintain its protective functions at higher operating temperatures, specifically by preventing silicate glass formation that would otherwise occur at elevated temperatures in sulfate-containing environments, thus enabling the engine to operate at higher temperatures with improved efficiency.
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-layer EBC system effectively slows and prevents silicate glass formation, enhancing the durability and corrosion resistance of silicon-based components in high-temperature gas turbine engine environments by raising the melting point and decreasing the basicity of the corrosive solution.
Implementation Method 1
the cerium oxide reduces formation of silicate glass on the substrate upon exposure to corrodant sulfates
Implementation Method 2
raising the melting point and decreasing the basicity of the corrosive solution
Implementation Method 3
The EBCs inhibit formation of volatile silicon species, Si(OH)x and SiO, thereby reducing recession and mass loss
Data Source
Figure 1
AI summary
In accordance with an embodiment of the invention, an article is disclosed which comprises a gas turbine engine component substrate comprising a silicon material; and an environmental barrier coating overlying the substrate, wherein the environmental barrier coating comprises cerium oxide, and the cerium oxide reduces formation of silicate glass on the substrate upon exposure to corrodant sulfates.