CMAS Mitigation Layer in Environmental Barrier Coatings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current environmental barrier coatings (EBCs) for ceramic components in gas turbine engines are susceptible to degradation due to the formation of calcium magnesium aluminosilicate (CMAS) deposits, which react with BSAS at high temperatures, leading to material loss and reduced component life.
Innovation Solution
Incorporating a CMAS mitigation composition, specifically Lna4Ga2O9, as a separate or integrated layer within the EBC, where Lna refers to rare earth elements like lanthanum, cerium, and gadolinium, to prevent degradation by CMAS deposits, either as a discrete refractory particle or grain boundary phase, within the coating structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional three-layer EBC system (bond coat, transition layer, outer layer) is used for ceramic components in high temperature sections, then the component achieves basic environmental protection and hermetic sealing, but the coating degrades over time due to reaction with CMAS deposits formed in the combustion environment
Solution Approach 1:
The EBC system is divided into multiple functional layers: a bond coat layer for adhesion, a transition layer (comprising at least one layer) for gradual property transition, and an outer layer for environmental protection. This segmentation allows each layer to address specific degradation mechanisms, with the transition layer specifically designed to resist CMAS penetration and reaction.
Solution Approach 2:
The transition layer is formulated as a composite material containing BSAS (barium strontium aluminosilicate) and rare earth disilicate particles. This composite composition provides both mechanical integrity and chemical resistance to CMAS, creating a barrier that prevents the harmful reaction between CMAS and the substrate while maintaining the hermetic seal.
2Loss of substance
If the EBC is designed to be hermetic to prevent gas penetration, then material loss is reduced, but mechanical stress from thermal expansion mismatch between coating and substrate increases
Solution Approach 1:
Different layers of the EBC are designed with different porosity characteristics. The transition layer is formulated with controlled porosity that provides both hermetic sealing properties and mechanical compliance. This local quality variation allows the coating to maintain its seal while accommodating thermal expansion differences between the ceramic substrate and metal bond coat through the gradual property transition in the intermediate layer.
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 CMAS mitigation composition effectively prevents the reaction of CMAS with the EBC, reducing material loss and maintaining the hermetic seal, thereby extending the life and performance of ceramic components in high-temperature environments.
Implementation Method 1
The CMAS mitigation composition effectively prevents the reaction of CMAS with the EBC, reducing material loss and maintaining the hermetic seal
Implementation Method 2
EBCs can provide a dense, hermetic seal against the corrosive gases in the hot combustion environment
Implementation Method 3
the silicon oxide reacts rapidly with high temperature steam, such as found in gas turbine engines, to form volatile silicon species. This oxidation/volatilization process can result in significant material loss, or recession
Implementation Method 4
aluminum oxide reacts with high temperature steam to form volatile aluminum species as well
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Calcium magnesium aluminosilcate (CMAS) mitigation compositions selected from zinc aluminate spinel, alkaline earth zirconates, alkaline earth hafnates, rare earth gallates, beryl, and combinations thereof wherein the CMAS mitigation composition is included as a separate CMAS mitigation layer in an environmental barrier coating for a high temperature substrate component.