Tape Casting Coating for Ceramic Matrix Composites
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Solution Overview
Problem
Current thermal spray processes for coating ceramic matrix composites, such as air plasma spray, face challenges including preferential volatilization of elements, amorphous microstructure, and limited ability to coat complex geometries, leading to changes in coating chemistry and microstructure that affect mechanical and chemical integrity.
Innovation Solution
The use of tape cast coatings with multiple layers or segments, each with controlled microstructure and chemistry, applied using techniques like slurry casting, tape casting, or gel casting, which allows for precise control over phase distribution, grain size, and sintering conditions, enabling coatings on complex geometries and repairing damaged areas without altering the coating chemistry during processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal spray processes (e.g., air plasma spray) are used to coat ceramic matrix composites, then coating application is achieved, but preferential volatilization of elements and amorphous microstructure occur, changing coating chemistry and microstructure
Solution Approach 1:
The patent replaces thermal spray processes (air plasma spray) with tape casting technology to apply coatings on ceramic matrix composites. This substitution eliminates the preferential volatilization and amorphous microstructure problems inherent in thermal spray, while maintaining coating application capability. The tape casting process allows precise control over coating chemistry and microstructure through controlled slurry deposition and sintering.
Solution Approach 2:
The patent employs controlled sintering parameters (temperature, time, atmosphere) during tape casting to achieve desired coating microstructure and chemistry. By adjusting these parameters, the coating can be densified while preserving chemical composition and creating controlled pore structures, thereby resolving the volatility and microstructure issues of thermal spray methods.
2Ease of manufacture
If thermal spray processes are used for coating, then coating can be applied to substrates, but the ability to coat complex geometries is limited
Solution Approach 1:
The patent divides the coating system into multiple tape layers, each capable of being independently designed and applied to specific regions of complex geometries. This segmentation allows different coating materials and properties to be applied to different areas, enabling comprehensive coverage of complex shapes that would be difficult to achieve with conventional thermal spray.
Solution Approach 2:
The tape casting approach introduces a dimensional advantage by allowing coatings to be applied in planar segments that can conform to complex three-dimensional geometries. The ability to create multi-layered, multi-segmented tape structures enables coating of shadowed regions and complex contours that are inaccessible to thermal spray processes.
3Ease of manufacture
If conventional coating methods are used, then coating can be applied to substrates, but cracking occurs and mechanical integrity is compromised
Solution Approach 1:
The patent utilizes controlled porosity in the coating structure, achieved through tape casting and sintering parameters, to reduce cracking and improve mechanical integrity. The controlled pore structures allow for stress relief while maintaining coating integrity, preventing the cracking that occurs with conventional coating methods.
Solution Approach 2:
The patent employs composite coating structures with multiple layers and segments, each with tailored properties, to enhance mechanical integrity. The composite structure includes different coating materials and pore configurations that work together to reduce cracking and improve overall mechanical strength while maintaining coating application capability.
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
This approach results in coatings with reduced cracking, improved chemical resistance, and enhanced mechanical integrity, capable of being applied to complex geometries and damaged regions, maintaining the desired chemistry and microstructure, and providing effective thermal and environmental protection.
Implementation Method 1
heating the braze tape to melt a constituent of at least one of the first coating material and the second coating material to form a densified coating on the surface of the substrate
Implementation Method 2
forming a braze tape defining at least one layer extending in a plane. The at least one layer includes a first segment including a first coating material and a second segment including a second coating material
Data Source
AI summary
The disclosure describes braze tape coatings and technique to form articles with differing physical properties in different layers or regions of the article. An example method includes forming a braze tape defining at least one layer that includes a first segment and a second segment. A portion of the second segment in the plane is adjacent to a portion of the first segment in a plane of the layer. The method also includes positioning the braze tape on a surface of a substrate, the plane of the layer of the braze tape being parallel to the surface of the substrate. The method also includes heating the braze tape to melt a constituent of at least one of the first coating material and the second coating material to form a densified coating on the surface of the substrate.