Multilayer CMAS-Resistant Barrier Coating for Gas Turbines
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Solution Overview
Problem
High-temperature gas turbine components face degradation due to calcia-magnesia-alumina-silicate (CMAS) deposits, which infiltrate porous thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs), increasing thermal conductivity and reducing their effectiveness, leading to substrate exposure and potential corrosion.
Innovation Solution
A multilayer coating structure comprising CMAS-resistant layers made of rare earth oxides and alumina, alternating with thermal or environmental barrier coating layers, which prevent CMAS infiltration and react with CMAS to form solid or viscous products, reducing thermal conductivity and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a porous thermal barrier coating (TBC) is used to reduce thermal conductivity, then thermal insulation is improved, but CMAS infiltration increases leading to degradation
Solution Approach 1:
The coating system is divided into multiple functional layers: a porous TBC layer for thermal insulation and a dense EBC layer for CMAS protection. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between porosity-based insulation and infiltration resistance.
Solution Approach 2:
The patent employs a composite coating structure combining TBC (yttria-stabilized zirconia) and EBC (mullite or rare earth silicate) materials. The composite architecture leverages the low thermal conductivity of TBC while utilizing the dense, CMAS-resistant properties of EBC materials to prevent infiltration, thus resolving the technical contradiction.
2Loss of energy
If the TBC is made strain-tolerant with porous structure, then thermal conductivity is reduced, but CMAS infiltration and subsequent strain damage increase
Solution Approach 1:
The coating is segmented into a porous TBC layer optimized for thermal insulation and a dense EBC layer that provides mechanical strength and strain tolerance. The dense EBC layer prevents CMAS infiltration that would cause strain damage, while the porous TBC maintains low thermal conductivity, resolving the contradiction between energy loss reduction and strength maintenance.
3Device complexity
If a single-layer TBC is used to simplify the coating structure, then manufacturing complexity is reduced, but CMAS protection capability is insufficient
Solution Approach 1:
The patent implements a composite TBC-EBC coating structure where the TBC provides thermal insulation and the EBC provides CMAS resistance. This composite approach enhances protection against CMAS attack while maintaining a relatively simple two-layer structure that can be applied using conventional coating techniques, thus resolving the contradiction between structural simplicity and harmful factor resistance.
4Productivity
If the operating temperature is increased to improve efficiency, then productivity is improved, but substrate temperature exposure increases requiring better barrier protection
Solution Approach 1:
The composite TBC-EBC coating system provides enhanced thermal insulation to maintain lower substrate temperatures while allowing higher gas path temperatures for improved efficiency. The dense EBC layer also prevents CMAS infiltration that would compromise substrate protection at elevated temperatures, resolving the contradiction between productivity improvement and temperature control.
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 multilayer coating significantly reduces CMAS infiltration, maintains thermal insulation, and prolongs the lifespan of barrier coatings by preventing CMAS-induced strain and corrosion, thus improving the operational efficiency and reliability of high-temperature mechanical systems.
Implementation Method 1
react with CMAS to form solid or viscous products
Implementation Method 2
maintains thermal insulation
Data Source
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AI summary
An article comprising a substrate, a calcia -magnesia - alumina - silicate - resistant (CMAS -resistant) layer or a plurality thereof, including a rare earth oxide and alumina formed over the substrate, and a barrier coating layer formed on the CMAS - resistant layer. The barrier coating layer or a plurality thereof, comprising a thermal barrier coating composition or an environmental barrier coating composition.