Rare Earth Disilicate Environmental Barrier Coating for CMC Recession
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Solution Overview
Problem
Ceramic matrix composite (CMC) materials used in high-temperature gas turbines are prone to corrosion due to the oxidation of SiC to silica, leading to recession and reduced lifetime, and existing environmental barrier coatings are sensitive to recession and inadequate against oxidizing species.
Innovation Solution
A novel environmental barrier comprising a rare earth disilicate (REa2Si2O7) with a rare earth oxide (REb2O3) in specific molar proportions, along with a rare earth monosilicate (REc2SiO5) layer, is applied to the substrate to enhance barrier effectiveness against oxidizing species and recession, while maintaining compatibility and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rare earth silicate layer is used as environmental barrier coating, then adhesion and oxygen protection are improved, but the coating is sensitive to recession and evaporates in operation
Solution Approach 1:
The patent modifies the chemical composition parameters of the environmental barrier coating by incorporating rare earth oxides (REb2O3) at controlled concentrations (0.1-30 at%) into the rare earth disilicate matrix. This compositional parameter change reduces the coating's sensitivity to recession and evaporation while maintaining its protective functions, thereby extending the coating's operational lifetime without sacrificing its oxidation protection capability.
Solution Approach 2:
The patent creates a composite environmental barrier coating material by combining rare earth disilicate (REa2Si2O7) with rare earth oxide (REb2O3) phases. This composite structure leverages the complementary properties of both components: the disilicate provides structural integrity and adhesion, while the oxide phase reduces recession sensitivity and evaporation, resulting in a more durable coating system.
2Object-affected harmful factors
If existing environmental barrier coatings are applied to CMC substrates, then some protection is provided, but the barrier effect against oxidizing species is inadequate
Solution Approach 1:
The patent optimizes the chemical composition parameters of the environmental barrier coating by incorporating rare earth oxides (REb2O3) at controlled concentrations (0.1-30 at%) into the rare earth disilicate matrix. This compositional parameter change reduces the coating's sensitivity to recession and evaporation while maintaining its protective functions, thereby extending the coating's operational lifetime without sacrificing its oxidation protection capability.
Solution Approach 2:
The patent employs a sacrificial oxide phase (REb2O3) that preferentially reacts with harmful CMAS deposits and oxidizing species, protecting the underlying CMC substrate. This disposable-like mechanism allows the oxide phase to be consumed or degraded in place of the valuable CMC substrate, extending the overall system lifetime.
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 proposed solution significantly improves the barrier effect against oxidizing species and recession, extending the lifetime of CMC materials at high temperatures in oxidizing and wet environments, and effectively withstands calcium and magnesium aluminosilicates (CMASes).
Implementation Method 1
the rare earth oxide REb2O3 presents greater reactivity with CMASes in comparison with the rare earth silicate and therefore reacts preferentially therewith so as to form compounds that are thermochemically stable
Implementation Method 2
the presence of the rare earth oxide REb2O3 in the first layer in particular proportions serves advantageously to confer on the environmental barrier a better barrier effect against diffusion of oxidizing species
Implementation Method 3
The corrosion of the CMC is the result of SiC oxidizing to silica, which, in the presence of water vapor, evaporates in the form of silicon hydroxide Si(OH)4
Implementation Method 4
silica, which, in the presence of water vapor, evaporates in the form of silicon hydroxide Si(OH)4
Data Source
AI summary
A part includes a substrate, having, adjacent to a surface of the substrate, at least a portion that is made from a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier including at least a first layer including a rare earth disilicate of formula REa2Si2O7 present at a molar content lying in the range 70% to 99.9%, where REa is a rare earth element; and at least one rare earth oxide of formula REb2O3 present at a molar content lying in the range 0.1% to 30%, where REb is a rare earth element different from REa.