Boron-Doped Environmental Barrier Coatings for TGO Stability
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Solution Overview
Problem
Ceramic or ceramic matrix composite materials used in high-temperature mechanical systems react with water vapor, leading to the formation of amorphous silicon dioxide thermally grown oxide (TGO) that crystallizes and cracks, causing spallation of the coating system, which reduces the component's useful lifetime.
Innovation Solution
A boron-doped environmental barrier coating (EBC) or borate layer is applied to inhibit or prevent the crystallization of TGO, controlling the TGO crystallization temperature regime to extend the component's usable life by maintaining the coating integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional environmental barrier coating is applied to protect ceramic or CMC materials from water vapor reaction, then the coating provides initial protection against environmental degradation, but the thermally grown oxide (TGO) layer crystallizes and cracks at high temperatures, causing spallation and reducing component lifetime
Solution Approach 1:
The patent applies boron doping to the EBC material, changing the chemical composition parameter of the coating. This parameter change modifies the crystallization behavior of the TGO layer, preventing crystal growth and maintaining coating integrity at high temperatures, thereby resolving the contradiction between initial protection and long-term durability
Solution Approach 2:
The patent creates a composite coating system by incorporating boron-doped EBC material with the base ceramic coating. This composite structure combines the protective properties of the EBC with the crystallization-inhibiting effects of boron, preventing TGO spallation and extending component lifetime while maintaining coating reliability
2Temperature
If the TGO layer is allowed to form naturally on the bond coat, then the coating system provides thermal protection, but the TGO crystallizes and cracks due to thermal cycling, causing spallation of the EBC
Solution Approach 1:
The boron-doped EBC acts as an intermediary layer between the bond coat and the external environment. It modifies the TGO formation process by incorporating boron into the oxide structure, which prevents crystallization and cracking while maintaining the thermal protection function of the coating system
Solution Approach 2:
By changing the chemical composition of the EBC through boron doping, the patent alters the physical and chemical properties of the TGO layer. This parameter change prevents the phase transformation that leads to cracking, thereby maintaining TGO structural stability under thermal cycling while preserving thermal protection
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 boron-doped EBC prevents TGO crystallization, thereby increasing the component's usable life by maintaining coating integrity and resisting spallation under high-temperature conditions.
Implementation Method 1
A boron-doped environmental barrier coating (EBC) or borate layer is applied to inhibit or prevent the crystallization of TGO, controlling the TGO crystallization temperature regime to extend the component's usable life by maintaining the coating integrity.
Data Source
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AI summary
The disclosure describes articles having coating systems configured to inhibit or prevent crystallization of TGO at the operating temperature of the article. An article includes a substrate defining a surface; a bond coat on the surface of the substrate; a coating layer that includes a boron dopant configured to inhibit crystallization of amorphous silicon dioxide thermally grown oxide on the bond coat at an operating temperature of the article. By inhibiting or preventing TGO crystallization, the described coating systems may increase a useable life of the component.