Self-Sealing Alkaline-Earth Aluminosilicate Coating for Hermeticity
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Solution Overview
Problem
Current environmental barrier coatings (EBCs) for high-temperature materials suffer from open porosity due to microcracks, allowing rapid penetration of water vapor and other species, leading to accelerated deterioration, and existing methods to address this issue are either challenging to implement or provide incomplete hermeticity.
Innovation Solution
A self-sealing and substantially hermetic coating system using an alkaline-earth aluminosilicate layer with a specific compositional range, which forms a flowable phase at a sealing temperature to fill defects and enhance barrier properties, reducing gas permeability to below 2×10−14 cm2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If plasma spray process is used to deposit EBC coatings, then flexibility to deposit various materials and wide spectrum of thicknesses is achieved, but open porosity in the form of microcracks is formed providing rapid path for water vapor penetration
Solution Approach 1:
The patent changes the chemical composition parameters of the sealing layer by incorporating specific ratios of silica (40-70 wt%), alumina (20-40 wt%), and alkaline earth oxides (10-30 wt%). This compositional parameter change enables the material to form a glassy phase at service temperatures that seals microcracks, transforming the coating from porous to hermetic while maintaining plasma spray processability
Solution Approach 2:
The patent creates a composite sealing layer combining multiple oxide components (silica, alumina, and alkaline earth oxides like BaO and SrO) that work synergistically. The silica provides glass-forming capability, alumina contributes to structural stability, and alkaline earth oxides lower the softening temperature, together forming a composite material that seals cracks effectively at service temperatures
2Reliability
If post-deposition impregnation process is used to fill pores with precursors, then coating permeability is improved, but multiple cycles are required and hermeticity may still be incomplete
Solution Approach 1:
The patent incorporates pore-sealing capabilities directly into the sealing layer composition during the initial deposition process. The glass-forming composition is designed to self-seal microcracks and pores when exposed to service temperatures, eliminating the need for subsequent impregnation treatments. This preliminary incorporation of sealing functionality reduces processing complexity while achieving complete hermeticity
3Reliability
If sealing layer with flowable phase is heated to sealing temperature, then cracks and pores are filled improving hermeticity, but energy consumption increases
Solution Approach 1:
The patent modifies the thermal parameters of the sealing layer by incorporating alkaline earth oxides (BaO and SrO) that significantly lower the glass transition and softening temperatures of the glassy phase. This parameter change enables crack sealing to occur at reduced temperatures (around 900-1100°C) compared to conventional coatings, thereby reducing the energy input required for the sealing process while maintaining effective hermeticity
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 coating system effectively seals cracks and pores, significantly reducing water vapor penetration and degradation of underlying materials, achieving improved hermeticity and extended service life with economic and reproducible methods.
Implementation Method 1
heating the sealing layer to a sealing temperature at which at least a portion of the sealing layer will flow
Implementation Method 2
Current EBC technology generally uses plasma spray processes to deposit the coatings
Data Source
AI summary
An article for use in aggressive environments is presented. In one embodiment, the article comprises a substrate and a self-sealing and substantially hermetic sealing layer comprising an alkaline-earth aluminosilicate disposed over the bondcoat. The substrate may be any high-temperature material, including, for instance, silicon-bearing ceramics and ceramic matrix composites. A method for making such articles is also presented. The method comprises providing a substrate; disposing a self-sealing alkaline-earth aluminosilicate layer over the substrate; and heating the sealing layer to a sealing temperature at which at least a portion of the sealing layer will flow.