Rare Earth Disilicate Monosilicate Gradient Coatings
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Solution Overview
Problem
High-temperature ceramic components in gas turbine engines face erosion due to reactive water vapor in combustion environments, and existing environmental barrier coatings (EBCs) often spall at temperatures exceeding their capabilities, necessitating a coating system that provides both environmental and thermal protection at temperatures of 2850° F (1565° C) or greater without using sintering aids.
Innovation Solution
A sintering-aid free coating system with a composition gradient, comprising a substrate coated with layers of rare earth disilicate and monosilicate, where the surface layer is predominantly rare earth disilicate, transitioning to predominantly rare earth monosilicate deeper in the coating, without the use of sintering aids, to provide thermal and environmental protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If environmental barrier coatings are applied to protect ceramic materials from erosion, then erosion resistance is improved, but the coating system spalls at high temperatures exceeding EBC capabilities
Solution Approach 1:
The coating system is divided into multiple layers with distinct functions: an environmental barrier coating layer for erosion protection and a thermal barrier coating layer for thermal protection. This segmentation allows each layer to specialize in protecting against specific harmful factors without compromising the other.
Solution Approach 2:
The patent employs a composite coating system combining rare earth disilicate and rare earth monosilicate materials with different properties. The disilicate provides erosion resistance while the monosilicate provides thermal protection, creating a composite system that delivers both benefits simultaneously.
2Ease of manufacture
If sintering aids are used in coating formation, then coating manufacturing is facilitated, but remelting occurs at high temperatures causing coating failure
Solution Approach 1:
The patent removes sintering aids from the coating formulation entirely, replacing them with alternative sintering mechanisms that do not involve low-melting-point additives. This extraction eliminates the source of remelting problems while maintaining coating formation capability through solid-state sintering processes.
Solution Approach 2:
The patent changes the sintering parameters by using elevated sintering temperatures (above 1700°C) and extended sintering times to achieve complete densification without sintering aids. This parameter change allows the coating to reach sufficient density and strength through solid-state diffusion mechanisms alone.
3Reliability
If a composition gradient is implemented in the coating system, then thermal and environmental protection are optimized, but manufacturing complexity increases
Solution Approach 1:
The coating system implements local quality by creating a composition gradient where the ratio of disilicate to monosilicate varies through the thickness of the coating. The disilicate-rich region near the substrate provides erosion protection, while the monosilicate-rich region at the surface provides thermal protection, with intermediate regions providing smooth transitions.
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 coating system effectively prevents erosion and spallation, offering improved thermal and environmental protection at high temperatures by avoiding the remelting issues associated with sintering aids and maintaining a solid state phase during sintering, resulting in enhanced durability and performance.
Implementation Method 1
The coating system is formed without using a sintering aid, maintaining a solid state phase during sintering
Data Source
AI summary
Components and methods for producing such components are provided. The component comprises a substrate having a ceramic material, and a coating system on a surface of the substrate. The coating system includes one or more layers defining a composition gradient. A first portion of the coating system closest to the surface of the substrate has a composition comprising at least 95 wt. % of a rare earth disilicate, a second portion of the coating system furthest from the surface of the substrate has a composition comprising at least 50 wt. % of a rare earth monosilicate, and a third portion between the first portion and the second portion has a composition comprising both the rare earth disilicate and the rare earth monosilicate.