Ceramic Matrix Composite Endface Coating for Turbine Recession
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Solution Overview
Problem
Ceramic matrix composite components in gas turbines experience recession and off-gassing issues at high temperatures, leading to reduced turbine aerodynamics and efficiency due to purge flow.
Innovation Solution
A coated ceramic matrix composite component with an environmental barrier coating on the endface surface, comprising a substrate with a hot gas path surface and an endface surface at an angle, utilizing a bond coat, thermally grown oxide layer, and top coat to prevent recession.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If purge flow is used to cool the surface of components below the recession temperature, then the component temperature is controlled, but turbine aerodynamics and overall turbine efficiency are reduced
Solution Approach 1:
An environmental barrier coating is applied as an intermediary layer between the hot gas path and the ceramic matrix composite component. This coating acts as a protective mediator that prevents direct thermal and chemical interaction, allowing the component to operate at higher temperatures without requiring purge flow for cooling, thereby maintaining turbine efficiency while protecting the component from thermal degradation
Solution Approach 2:
The invention uses a multi-layer environmental barrier coating system comprising different material layers (bond coat, transition layer, top coat) with complementary properties. This composite coating structure provides both thermal barrier functionality and chemical resistance, enabling the CMC component to withstand high-temperature environments without purge flow, thus resolving the contradiction between temperature control and turbine efficiency
2Reliability
If environmental barrier coating is applied to the endface surface, then recession is prevented and component lifespan is prolonged, but manufacturing complexity increases
Solution Approach 1:
The environmental barrier coating is segmented into multiple functional layers: a bond coat layer for adhesion, a transition layer for thermal gradient management, and a top coat layer for environmental protection. This segmentation allows each layer to be optimized for its specific function and enables the coating to be applied using standard multi-step ceramic coating processes, managing complexity through functional decomposition
Solution Approach 2:
The environmental barrier coating is applied selectively to the endface surface where recession occurs, rather than uniformly across the entire component. This localized application targets the specific problem area (endface surface exposed to hot gases) while minimizing the overall complexity and material usage of the coating system
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 environmental barrier coating effectively prevents recession, prolonging the component's lifespan and maintaining turbine efficiency by protecting against high-temperature degradation.
Implementation Method 1
an environmental barrier coating on at least a portion of the endface surface... effectively prevents recession, prolonging the component's lifespan and maintaining turbine efficiency by protecting against high-temperature degradation
Data Source
AI summary
A coated ceramic matrix composite component and a gas turbine assembly are provided. The coated ceramic matrix composite component comprises a substrate comprising an endface surface and a hot gas path surface. The hot gas path surface is arranged and disposed to contact a hot gas path when the component is installed in the gas turbine assembly. The endface surface is disposed at an endface angle to the hot gas path surface and opposing at least one adjacent component when the component is installed in the gas turbine assembly. The coated ceramic matrix composite component further comprises an environmental barrier coating on at least a portion of the endface surface.