Thermal Barrier Coating Adhesion via Vertical Cracks
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Solution Overview
Problem
Current thermal barrier coatings for gas turbines lack high strain tolerance and adhesion, particularly when applied using plasma spray processes, which are also expensive and limited in scalability, and require extensive surface preparation.
Innovation Solution
A coating with a unique microstructure comprising elongate material growth domains of high intra-domain density and equiaxed grain morphology, or a matrix with vertically oriented cracks, achieved through air plasma spray techniques, providing enhanced adhesion and strain tolerance without the need for extensive surface preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma spray processes are used to deposit thermal barrier coatings, then the coating can be applied to large components at lower cost with greater scalability, but the coating exhibits lower strain tolerance and substrate adhesion compared to PVD processes
Solution Approach 1:
The coating incorporates vertically oriented cracks distributed throughout the coating structure, creating localized compliant regions that accommodate thermal expansion strain while maintaining overall coating integrity and adhesion to the substrate
Solution Approach 2:
The coating combines ceramic material with a controlled network of vertical cracks to create a composite microstructure that provides both thermal barrier functionality and strain tolerance, achieving PVD-level performance through plasma spray deposition
2Ease of manufacture
If traditional thermal spray processes are used to deposit thermal barrier coatings, then the coating can be applied with simplified equipment, but the coating requires ancillary surface preparation processes such as grit blasting and deposition of rough bond coats to achieve adequate adhesion
Solution Approach 1:
The plasma spray process inherently creates a coating microstructure with vertical cracks and appropriate surface characteristics that provide self-adhesion to the substrate, eliminating the need for separate surface preparation steps like grit blasting or bond coat deposition
3Reliability
If PVD processes are used to deposit thermal barrier coatings, then the coating achieves high strain tolerance and adhesion, but the process is relatively expensive and applicable to relatively small components due to vacuum chamber requirements
Solution Approach 1:
The patent replaces the vacuum-based PVD deposition mechanism with atmospheric plasma spray deposition, using a different physical mechanism (melted particle impact and bonding) to achieve similar coating microstructures and performance characteristics without requiring vacuum equipment
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 solution achieves adhesion and strain tolerance comparable to PVD-deposited coatings but at a lower cost and with greater scalability, using air plasma spray processes, resulting in durable thermal barrier coatings suitable for high-temperature applications.
Implementation Method 1
air plasma spray techniques
Implementation Method 2
comprise a plurality of at least partially melted and solidified particles
Data Source
AI summary
Coatings and articles suitable for use in high temperature environments, for example, are presented. One embodiment is a coating that comprises a plurality of elongate material growth domains defined between domain boundaries. The domains have an intra-domain density of at least about 75% of theoretical density, have a substantially equiaxed grain morphology, and comprise a plurality of at least partially melted and solidified particles. Another embodiment is a coating that comprises a matrix comprising a substantially equiaxed grain morphology and a plurality of vertically oriented cracks disposed in the matrix. Further embodiments include articles comprising one or more of the coatings described above.