Environmental Barrier Coating Sintering Aids for Steam Corrosion
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Solution Overview
Problem
Current environmental barrier coatings (EBCs) for high-temperature ceramic components in gas turbine engines face challenges such as oxidation and volatilization in steam environments, leading to dimensional changes and corrosion, which existing coating processes like plasma spray and vapor deposition fail to adequately address.
Innovation Solution
A method using solvent-based slurries with sintering aids to form dense EBC layers, comprising a bond coat, transition layer, optional silica layer, compliant layer, and outer layer, which can be applied through various processes to lower sintering temperatures and provide a hermetic seal, protecting components from high-temperature corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard industrial coating processes (plasma spray, vapor deposition) are used to apply EBCs, then coating can be applied to ceramic components, but the coating density and hermetic seal quality are insufficient, allowing steam penetration and corrosion
Solution Approach 1:
The patent changes the chemical composition parameters of the coating by incorporating specific glass phases with controlled ratios of network formers (SiO2, B2O3), network modifiers (Na2O, K2O, CaO), and intermediate oxides (Al2O3). This compositional parameter optimization enables the coating to achieve dense microstructure and hermetic seal properties that prevent steam penetration, while maintaining compatibility with standard industrial coating processes
Solution Approach 2:
The patent employs composite material design by creating a multi-phase glass system combining network formers, modifiers, and intermediates. This composite glass structure synergistically provides both the hermetic sealing capability (through dense network former content) and the manufacturability (through modifiers that facilitate processing and bonding to the substrate)
2Temperature
If higher operating temperatures are used to improve gas turbine efficiency, then engine performance increases, but oxidation and volatilization of ceramic components accelerate
Solution Approach 1:
The patent creates a protective inert environment at the ceramic component surface through the glass-based EBC. The glass matrix forms a dense, chemically stable barrier that acts as an inert protective layer, preventing oxygen and steam from reaching the silicon-containing CMC substrate. This eliminates oxidation and volatilization reactions even at elevated operating temperatures, allowing the component to maintain its mechanical properties and dimensional stability
Solution Approach 2:
The patent converts the potentially harmful interaction between steam and ceramic into a beneficial protective mechanism. The glass coating is designed to be slightly porous at high temperatures, allowing controlled steam ingress that triggers formation of a protective silica-rich layer at the coating-substrate interface. This transforms the harmful steam environment into a self-healing protective barrier that further enhances oxidation resistance
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 method achieves a highly dense, durable EBC that prevents penetration by hot steam and maintains mechanical properties, offering improved uniformity and cost-effectiveness compared to conventional techniques, while allowing for internal component coating and smooth surface finishes.
Implementation Method 1
Methods for making environmental barrier coatings using sintering aids suitable for use with high temperature components
Data Source
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AI summary
Methods for making an environmental barrier coating using a sintering aid involving applying a bond coat layer to the ceramic component; combining at least an organic solvent, a primary transition material selected from a rare earth disilicate, or a doped rare earth disilicate, and at least one slurry sintering aid to produce a transition layer slurry; combining at least an organic solvent, and a primary outer material selected from a rare earth monosilicate or a doped rare earth monosilicate to produce an outer layer slurry; combining at least an organic solvent, and a primary compliant material comprising BSAS or a rare earth doped BSAS to produce a compliant layer slurry; applying at least the transition layer slurry, and any one or more of the outer layer slurry, and the compliant layer slurry to the component; and sintering the component to produce the environmental barrier coating having at least the bond coat layer, a transition layer and any of an outer layer or a compliant layer whereby a reaction between the primary materials and the slurry sintering aid results in the transition layer having a porosity of from 0% to about 15% by volume of the transition layer, the outer layer having a porosity of from 0% to about 30% by volume of the outer layer, and the compliant layer having a porosity of from about 0% to about 30% by volume of the compliant layer.