CMAS Mitigation Layer for Environmental Barrier Coatings

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Solution Overview

Problem

High-temperature gas turbine engine components face material loss and degradation due to CMAS deposits, which interact with existing environmental barrier coatings (EBCs) and react with steam, leading to volatilization and loss of protective layers, compromising component life and performance.

Innovation Solution

Incorporation of a calcium magnesium aluminosilicate (CMAS) mitigation composition, specifically cordierite, as a separate or integrated layer within the EBC system, including a bond coat, transition layers, and an optional outer layer, to prevent CMAS interaction and volatilization, enhancing the durability and longevity of ceramic components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If BSAS is used in the transition or outer layer to provide environmental protection, then the coating provides hermetic seal and mechanical integrity, but CMAS interacts with BSAS at high temperatures causing detrimental reaction byproducts and volatilization

Engineering Contradiction:

ImproveEBC protection performanceVSAvoidCMAS interaction and volatilization

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A CMAS mitigation layer comprising cordierite or cordierite-forming composition is introduced between the EBC layers (containing BSAS) and the CMAS deposits. This intermediary layer prevents direct interaction between CMAS and BSAS, blocking the harmful chemical reactions and volatilization processes while allowing the EBC to maintain its protective function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention utilizes the refractory nature of cordierite (high melting point, chemical stability) to convert the harmful effect of CMAS deposits into a beneficial protective function. The CMAS mitigation layer is designed to interact with CMAS in a controlled manner, forming stable compounds that prevent further degradation of the EBC system.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Use of energy by moving object

If operating temperature is increased to improve gas turbine efficiency, then energy efficiency improves, but high temperature durability of components deteriorates due to accelerated CMAS interaction and volatilization

Engineering Contradiction:

Improvegas turbine efficiencyVSAvoidcomponent life

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The CMAS mitigation layer is applied in advance to the EBC system before CMAS deposits can cause damage. This preliminary protective measure is designed to intercept and neutralize CMAS deposits before they can interact with and degrade the EBC layers, thereby extending component life at elevated operating temperatures.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If a hermetic seal layer is used to prevent hot gas penetration, then protection against corrosive gases is improved, but thermal expansion mismatch stress increases due to porosity requirements for stress mitigation

Engineering Contradiction:

Improveprotection against corrosive gasesVSAvoidthermal expansion mismatch stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The EBC system is segmented into multiple functional layers: a hermetic seal layer (transition or outer layer containing BSAS) for gas barrier protection, and a separate CMAS mitigation layer for chemical stability. This segmentation allows each layer to be optimized for its specific function without compromising the other, managing both hermeticity and stress requirements.

Inventive Principle:

Principle #1Segmentation

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 degradation of EBCs by CMAS, reducing material loss and maintaining the hermetic seal, thereby extending the life and functionality of high-temperature components in gas turbine engines.

Implementation Method 1

BSAS and CMAS chemically interact at high temperatures, i.e. above the melting point of CMAS (approximately 1150°C to 1650°C)... the reaction byproducts formed by the interaction of BSAS and CMAS can be detrimental to EBCs

Methodology Applied

Scientific EffectChemical interaction prevention:

Implementation Method 2

the silica layer may be applied to the bond coat layer, or alternately, may be formed naturally or intentionally on the bond coat layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentEP2202212B1Components Comprising CMAS mitigation compositions

Publication Date: 2020.08.05 GENERAL ELECTRIC CO

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AI summary

Calcium magnesium aluminosilicate (CMAS) mitigation compositions selected from rare earth elements, rare earth oxides, zirconia, hafnia partially or fully stabilized with alkaline earth or rare earth elements, zirconia partially or fully stabilized with alkaline earth or rare earth elements, magnesium oxide, cordierite, aluminum phosphate, magnesium silicate, and combinations thereof when the CMAS mitigation composition is included as a separate CMAS mitigation layer (20) in an environmental barrier coating (12) for a high temperature substrate component.