Ceramic-Coated Substrate Edge Channels to Reduce TBC Spallation
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Solution Overview
Problem
Delamination or spalling of thermal barrier coatings from their underlying substrates in gas turbine engines due to differential thermal expansion and contamination, such as CMAS attack, which reduces the coating's ability to accommodate thermal deformations.
Innovation Solution
The implementation of a ceramic coating with a metallic substrate and a pattern of recesses and channels along the bevel surfaces, where the channels are of different sizes and registry, extending from the inner diameter surface to the circumferential ends, and a ceramic coating comprising a majority of YSZ or GSZ, applied using machining and grinding techniques to create faults that accommodate thermal stresses and reduce spallation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic coating is applied to a substrate in gas turbine engines, then thermal barrier protection is provided, but delamination or spalling occurs due to differential thermal expansion and CMAS attack
Solution Approach 1:
The coating system is segmented into multiple functional layers: a ceramic topcoat layer providing thermal barrier protection, a metallic intermediate layer (bond coat) providing oxidation resistance and thermal expansion accommodation, and a substrate layer. This segmentation allows each layer to perform its specific function while reducing overall delamination risk
Solution Approach 2:
The patent employs a composite material structure combining ceramic materials (for high-temperature resistance and thermal barrier properties) with metallic materials (for ductility and thermal expansion accommodation). The ceramic topcoat contains refractory aggregates and glass phase bonded with a metallic matrix, creating a composite that balances thermal performance with mechanical flexibility to accommodate differential thermal expansion
2Temperature
If the ceramic coating is made thicker to improve thermal barrier protection, then thermal resistance increases, but stress from differential thermal expansion increases leading to spallation
Solution Approach 1:
The composite ceramic-metallic structure allows the ceramic topcoat to be sufficiently thick for thermal protection while the metallic intermediate layer and substrate provide ductility to accommodate the resulting thermal stresses, preventing catastrophic spallation
Solution Approach 2:
The patent modifies the physical and chemical parameters of the coating system by controlling the glass phase composition, refractory aggregate content, and metallic matrix properties to optimize the balance between thermal resistance and stress accommodation capacity
3Object-affected harmful factors
If CMAS attack resistance is improved by modifying coating composition, then coating integrity against contamination increases, but ability to accommodate thermal expansion may be reduced
Solution Approach 1:
The composite structure with refractory aggregates and glass phase in a metallic matrix provides both CMAS resistance (through the refractory components that resist chemical attack) and thermal expansion accommodation (through the metallic matrix and intermediate layer that provide ductility)
Solution Approach 2:
The coating composition is optimized locally with refractory aggregates and glass phase concentrated in the ceramic topcoat where CMAS attack occurs, while the metallic intermediate layer maintains higher ductility content to accommodate thermal expansion stresses
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 effectively reduces spallation at high-temperature edges by accommodating thermal expansion and stress concentrations, enhancing the durability and thermal resistance of the ceramic coatings.
Implementation Method 1
Delamination or spalling of thermal barrier coatings from their underlying substrates is a significant problem. A principal driver of delamination is differential thermal expansion/contraction of the coating and the underlying substrate.
Implementation Method 2
With typical plasma spray coatings, the initiation may be the creation of boundaries/gaps between regions of the as-applied coating.
Data Source
AI summary
An article has a body having: a first face; and a first bevel surface extending from the first face. A plurality of first channels along the first bevel surface extending from the first face. A ceramic coating is along the inner diameter surface and the first bevel surface.