Ceramic Coating Bevel Channels for Thermal Spallation Resistance
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Solution Overview
Problem
Delamination and spalling of thermal barrier coatings in gas turbine engines due to differential thermal expansion and contamination, such as CMAS attack, which reduces the coating's ability to accommodate thermal expansion.
Innovation Solution
The substrate edges are modified with a bevel surface featuring an array of recesses and channels, with different-sized channels aligned in-phase and out-of-phase with the recesses, to create initiation sites for faults in the ceramic coating, accommodating thermal stresses and reducing spallation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a continuous ceramic coating is applied over a smooth substrate surface, then the coating provides complete coverage and uniform protection, but the coating is prone to delamination and spalling under thermal stress due to inability to accommodate differential thermal expansion
Solution Approach 1:
The substrate surface is segmented into recessed regions and unrecessed regions, creating an array of patterns that induce fault formation in the ceramic coating. This segmentation allows the coating to develop controlled boundaries that can accommodate thermal expansion differential, preventing large-scale delamination while maintaining overall coating integrity.
Solution Approach 2:
The substrate surface is pre-modified with recesses before ceramic coating application. This preliminary action creates predetermined initiation sites for faults in the coating, ensuring that when thermal stress occurs, the coating fails in a controlled manner through fault propagation rather than sudden delamination, thereby improving reliability.
2Reliability
If the substrate surface is modified with recesses and channels to induce fault formation, then the coating can accommodate thermal expansion and resist spallation, but the manufacturing process becomes more complex
Solution Approach 1:
The substrate surface is created with a porous-like structure consisting of recesses and channels. This structure is relatively simple to manufacture using conventional machining or additive manufacturing techniques, yet it effectively induces fault formation in the coating that accommodates thermal expansion, achieving spallation resistance without excessive manufacturing complexity.
Solution Approach 2:
The substrate surface geometry is modified by changing parameters such as recess depth, channel dimensions, and pattern spacing. These parameter changes create the necessary conditions for fault initiation while keeping the manufacturing process within reasonable complexity limits, balancing reliability improvement with ease of manufacture.
3Reliability
If larger recesses and channels are used to accommodate thermal stress, then the coating has more space for fault propagation and reduced spallation, but the structural strength and integrity of the substrate edge are reduced
Solution Approach 1:
The substrate surface features localized recesses and channels only in specific regions where ceramic coating is applied, while maintaining full structural integrity in load-bearing areas. This local modification provides fault accommodation space exactly where needed for thermal stress relief, without compromising the overall strength of the substrate edge.
Solution Approach 2:
The recesses and channels are designed with dimensions that are sufficient to induce fault formation and accommodate thermal expansion, but not so large as to significantly compromise substrate strength. The partial modification of the substrate surface provides just enough space for fault propagation while maintaining adequate structural integrity.
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 modified substrate edges enhance the ceramic coating's ability to withstand thermal stresses and reduce spallation, improving the durability and performance of the coating under harsh conditions.
Implementation Method 1
A principal driver of delamination is differential thermal expansion/contraction of the coating and the underlying substrate
Implementation Method 2
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
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.