Dual-Layer Environmental Barrier Coating for Crack-Resistant Turbines
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Solution Overview
Problem
Gas turbine engine components face challenges due to high temperatures, corrosive and oxidative conditions, and elevated stress levels, leading to degradation and reduced performance.
Innovation Solution
A composite barrier coating system comprising a bond coat with gettering and diffusive particles, and a dual-layer top coat with varying porosity and compliance, applied via thermal spray processes, to protect components from environmental and thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer top coat is applied to protect the bond coat, then the component gains thermal and oxidative stability, but segmentation cracking occurs due to thermal stress and compliance mismatch
Solution Approach 1:
The top coat is divided into two distinct layers: a first top coat layer with higher porosity and compliance adjacent to the bond coat, and a second top coat layer with lower porosity on the exterior. This segmentation allows each layer to perform its specific function - the first layer absorbs thermal stress and compliance mismatch, while the second layer provides oxidation protection, thereby preventing segmentation cracking while maintaining thermal and oxidative stability.
2Reliability
If a dense, low-porosity top coat is applied to improve oxidation resistance, then oxidative stability improves, but thermal stress and segmentation cracking increase due to rigidity
Solution Approach 1:
Different porosity levels are assigned to different locations within the top coat structure. The first top coat layer adjacent to the bond coat has higher porosity (10-20%) to provide compliance and absorb thermal stress, while the second exterior layer has lower porosity (5-15%) to provide oxidation resistance. This local quality differentiation allows the coating system to simultaneously achieve oxidation protection and stress tolerance.
3Strength
If the top coat is applied in multiple layers with different properties, then cracking is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The invention controls porosity as a key parameter to differentiate the two top coat layers. By specifying porosity ranges (first layer: 10-20%, second layer: 5-15%) and thickness ratios (first layer: 1.5-2.5 times the second layer thickness), the patent provides clear manufacturing guidelines that simplify the multi-layer coating process while achieving the desired crack resistance performance.
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 coating system enhances thermal and oxidative stability, reduces segmentation cracking, and improves mechanical protection and aerodynamic efficiency of gas turbine engine components.
Implementation Method 1
applying a first feedstock comprising particles of oxide-based material having diameters between about 1 and about 80 microns via a thermal spray process to form a first top coat layer
Implementation Method 2
applying a second feedstock comprising particles of oxide-based material having diameters between about 15 and about 60 microns via the thermal spray process to form a second top coat layer
Implementation Method 3
the method also includes curing or sintering the first and second top coat layers
Data Source
AI summary
A method of applying a top coat to an article according to an exemplary embodiment of this disclosure, among other possible things includes applying a first feedstock comprising particles of oxide-based material having diameters between about 1 and about 80 microns via a thermal spray process to form a first top coat layer on an article having a bond coat and applying a second feedstock comprising particles of oxide-based material having diameters between about 15 and about 60 microns via the thermal spray process to form a second top coat layer on the first top coat layer. An article and a barrier layer for an article are also disclosed.