Airfoil Tip Stress Mitigation via Surface Feature Arrays
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Solution Overview
Problem
High-temperature mechanical systems, such as gas-turbine engines, experience thermal stress due to temperature variations, leading to crack formation and delamination of thermal barrier coatings (TBCs) from substrates, primarily due to differing coefficients of thermal expansion and temperature gradients.
Innovation Solution
Forming arrays of features on the substrate surface, aligned with cooling holes, to disrupt the planarity and impede crack growth, segregating the substrate and TBC into smaller domains, thereby mitigating thermal stress and enhancing thermal protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arrays of features are formed on the substrate surface to disrupt planarity and impede crack growth, then thermal stress resistance and TBC lifespan are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The substrate surface is segmented into multiple domains by forming arrays of features (such as grooves, ridges, or protrusions) that divide the continuous surface into discrete regions. This segmentation prevents crack propagation across the entire surface by confining cracks within individual domains, thereby improving thermal stress resistance and extending TBC lifespan while adding controlled structural complexity.
2Reliability
If arrays of features are formed on the substrate surface to disrupt planarity and impede crack growth, then TBC delamination is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The arrays of features are formed on the substrate surface before applying the thermal barrier coating. This preliminary action ensures that the features are already in place to guide and constrain crack growth paths before the TBC is deposited, thereby improving bonding integrity while allowing for controlled manufacturing tolerances in the feature geometry that can be addressed in subsequent coating processes.
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 features effectively reduce crack propagation and delamination, improving the thermal stress resistance and lifespan of the TBC, while providing thermal protection to the exposed substrate areas.
Implementation Method 1
The stress may be due to, for example, the substrate/bond coat and TBC having different coefficients of thermal expansion, or the substrate/bond coat and TBC experiencing different temperatures due to thermal gradients
Implementation Method 2
The substrate can be coated with a thermal barrier coating (TBC) to reduce surface temperatures. The thermal barrier coating may include a thermally insulative ceramic topcoat
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 3A~3D
AI summary
An article may include an array of features formed in a substrate and may be coated with a coating layer. The array of features may mitigate stress experienced by the coated article. In particular, the array of features may reduce or limit crack propagation at the interface between the substrate and the coating layer. In some examples, the article is an airfoil that includes a tip that defines an edge. An array of features is formed on the surface of the tip, where the array of features is proximate to the edge, and the array of features does not intersect the edge. The airfoil includes a coating layer formed on the surface of the tip and the array of features.