Calcium Sulphate Layer Prevents CMAS Diffusion in Thermal Barrier Coatings
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Solution Overview
Problem
Yttria-based thermal barrier coatings are destabilized by calcia-alumina-magnesia silicate (CMAS) attacks, which can lead to spallation through Ca diffusion and solid-state reactions, necessitating a protective layer that does not react with environmental contaminants or the TBC material.
Innovation Solution
A protective layer of calcium sulphate (CaSO4) is applied adjacent to or infiltrating the chemically stabilized zirconia layer, which has a low or zero diffusion coefficient for calcium, preventing CMAS attack without reacting with environmental contaminants or the TBC material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial oxide coating is applied to protect the thermal barrier coating from CMAS attack, then the TBC is protected from contaminant infiltration, but the coating adds device complexity and requires additional manufacturing steps
Solution Approach 1:
The patent combines the protective function and thermal barrier function into a single integrated coating layer. The EBC layer is formulated with materials (such as rare earth aluminates, calcium aluminates, or strontium aluminates) that provide both CMAS resistance and thermal insulation properties, eliminating the need for separate sacrificial and TBC layers while maintaining protective functionality.
Solution Approach 2:
The environmental barrier coating layer is designed to perform multiple functions simultaneously: it acts as a protective barrier against CMAS attack, provides thermal insulation, and maintains structural integrity at high temperatures. This multi-functional design reduces the need for additional specialized layers.
2Reliability
If an impermeable barrier coating is applied to prevent CMAS infiltration, then the TBC is protected from contaminant penetration, but the coating increases device complexity and manufacturing difficulty
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating layer by incorporating specific materials such as rare earth aluminates, calcium aluminates, or strontium aluminates with controlled stoichiometric ratios. These compositional adjustments create an inherently CMAS-resistant coating that achieves protection through material selection rather than complex multi-layer structures, simplifying the manufacturing process.
3Reliability
If multiple protective coatings are applied to decrease CMAS infiltration, then the TBC protection is enhanced, but the device complexity and coating thickness increase
Solution Approach 1:
The patent merges the protective barrier function and thermal insulation function into a single integrated environmental barrier coating layer. This consolidation achieves both CMAS protection and thermal management in one layer, avoiding the need for multiple stacked coatings and reducing the total coating thickness while maintaining enhanced protection.
4Stability of the object's composition
If a protective layer is applied to prevent calcium diffusion into the TBC, then residual stresses and spallation are reduced, but the coating adds device complexity
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by using materials with low calcium solubility and high resistance to calcium diffusion, such as rare earth aluminates, calcium aluminates, or strontium aluminates with specific stoichiometric compositions. This compositional modification creates an inherently stable barrier against calcium diffusion, maintaining TBC integrity without requiring complex multi-layer structures.
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 calcium sulphate layer effectively prevents calcium diffusion into the TBC, reducing residual stresses and spallation, and maintaining the TBC's integrity under hot air flow conditions, as demonstrated by the absence of Ca diffusion and reaction layers in coated samples.
Implementation Method 1
A protective layer of calcium sulphate (CaSO4) is applied adjacent to or infiltrating the chemically stabilized zirconia layer, which has a low or zero diffusion coefficient for calcium
Implementation Method 2
preventing CMAS attack without reacting with environmental contaminants or the TBC material
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention pertains to components (1) with a thermal barrier coating (2-6) on the surface thereof, wherein the thermal barrier coating comprises at least one layer (3) comprising chemically stabilised zirconia, and wherein at least indirectly adjacent to the layer (3) comprising chemically stabilised zirconia and on its surface facing side there is provided a protective layer (4) and/or a infiltration zone (5) which is not reacting with environmental contaminant compositions that contain oxides of calcium and which is not reacting with the material of the layer (3) comprising chemically stabilised zirconia. It furthermore relates to methods for making such components as well as to uses of specific systems for coating thermal barrier coatings for the prevention of CMAS.