SiC/SiC Environmental Barrier Coating for High Temperature Oxidation
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Solution Overview
Problem
Current environmental barrier coatings for SiC/SiC ceramic matrix composites in gas turbines have limitations due to low temperature capability, mechanical fatigue, and oxidation resistance, particularly with silicon-based bond coats that melt below 1410°C, necessitating the development of high-temperature, non-silicon based bond coats for improved durability and thermal stability.
Innovation Solution
The development of advanced high-temperature environmental barrier coating systems featuring a bond coat system with silicon/silicide or oxide/silicate components, including rare earth doped silicon alloys and highly stable oxide/silicate materials, which provide enhanced adhesion, oxidation resistance, and self-healing capabilities, enabling operation up to 2700°F (1482°C) with reduced oxygen activity and thermal expansion matching Si-based ceramics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-based bond coats are used, then adhesion and oxidation resistance are improved, but temperature capability deteriorates due to melting below 1410°C
Solution Approach 1:
The patent employs composite bond coat systems combining silicon-based materials with rare earth silicates and other refractory compounds. This composite structure allows the coating to maintain the excellent adhesion and oxidation resistance of silicon-based materials while incorporating high-temperature stable phases that prevent melting and degradation above 1410°C, enabling operation at 2700°F (1482°C) and above.
2Ease of manufacture
If conventional EBC systems are used, then manufacturing simplicity is maintained, but durability under thermal cycling and mechanical fatigue deteriorates
Solution Approach 1:
The patent divides the environmental barrier coating into multiple functional layers including bond coat, intermediate layer, and top coat, each with specific compositions and functions. This segmented structure allows each layer to be optimized for particular properties (adhesion, thermal expansion matching, oxidation resistance) while collectively providing superior fatigue and thermal cycling resistance compared to conventional single-layer systems.
3Temperature
If high temperature oxide TBC and silicate EBC combined system is used, then temperature capability is improved, but coating complexity increases
Solution Approach 1:
The patent merges the thermal barrier function of oxide coatings with the environmental barrier function of silicate coatings into an integrated multi-layer system. By combining these functions in a structured sequence of layers with graded compositions, the system achieves high temperature capability (2700°F/1482°C and above) while managing complexity through functional integration rather than separate independent systems.
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 coating system significantly enhances the durability and thermal stability of SiC/SiC ceramic components, offering superior oxidation and fatigue resistance, self-healing properties, and improved environmental protection, enabling operation in extreme high-temperature conditions with reduced cooling requirements.
Implementation Method 1
an environmental barrier coating (EBC) system that can include a bond coat system
Implementation Method 2
thermal expansion matching Si-based ceramics
Implementation Method 3
coatings are frequently used to protect such components from those conditions... Environmental barrier coating (EBC) systems are thin ceramic layers, generally applied by plasma spraying and/or physical vapor deposition
Implementation Method 4
Environmental barrier coating (EBC) systems are thin ceramic layers, generally applied by plasma spraying and/or physical vapor deposition
Data Source
AI summary
Advanced environmental barrier coating bond coat systems with higher temperature capabilities and environmental resistance are disclosed. These bond coat systems can be applied to ceramic substrates such as SiC/SiC ceramic matrix composite substrates, and can provide protection from extreme temperature, mechanical loading and environmental conditions, such as in high temperature gas turbines. Example bond coat systems can include either an advanced silicon/silicide component, an oxide/silicate component, or a combination thereof.