Segmented Abradable Coatings for Gas Turbine Blade Protection
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Solution Overview
Problem
Current ceramic coatings in gas turbine engines suffer from excessive material loss due to erosion and spalling, leading to decreased turbine efficiency and blade damage, as they are not adequately resistant to abrasion and thermal stress.
Innovation Solution
A segmented ceramic coating process involving a bond coat layer, a 7 weight percent yttria-stabilized zirconia layer, and a 12 weight percent yttria-stabilized zirconia layer, where the 7YSZ layer promotes vertical crack propagation and the 12YSZ layer provides low thermal conductivity, enhancing toughness and spallation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If current ceramic coatings are used on duct segments, then wear resistance is improved, but material loss due to erosion and spalling increases
Solution Approach 1:
The ceramic coating is designed with controlled vertical cracks that segment the coating into distinct regions. This segmentation allows the coating to better accommodate thermal stresses and prevents large-scale spalling, thereby reducing material loss while maintaining wear resistance
Solution Approach 2:
The coating system uses a composite structure with multiple ceramic layers (7YSZ and 12YSZ) having different properties. The 7YSZ layer provides toughness and crack resistance, while the 12YSZ layer provides erosion resistance and low thermal conductivity, together resolving the contradiction between wear resistance and material loss
2Object-affected harmful factors
If ceramic coating thickness is increased to improve erosion resistance, then erosion resistance is improved, but thermal stress increases leading to more spalling
Solution Approach 1:
Different regions of the coating have different properties: the 7YSZ layer is designed to be tougher and more crack-resistant, while the 12YSZ layer is designed for erosion resistance and thermal insulation. This local differentiation allows the coating system to achieve both erosion resistance and spalling resistance simultaneously
Solution Approach 2:
The controlled vertical cracks segment the thick ceramic coating into manageable sections, allowing the coating to accommodate thermal expansion differences between layers and the substrate, thereby preventing delamination cracking and spalling even at increased thickness
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 offers improved abradability, erosion resistance, and reduced thermal conductivity, maintaining turbine efficiency and blade integrity by mitigating material loss and thermal stress effects.
Implementation Method 1
heating said article to expand the 7 weight percent yttria-stabilized zirconia layer and promote vertical crack propagation therein
Implementation Method 2
depositing an amount of bond coat material sufficient to form a bond coat layer upon at least one surface of an article
Implementation Method 3
a) depositing an amount of bond coat material sufficient to form a bond coat layer
Data Source
Figure 1
Figure 2A~2B
AI summary
A segmented abradable ceramic coating (20) comprises a bond coat layer (26), at least one segmented 7 weight percent yttria-stabilized zirconia layer (28) disposed upon said bond coat layer (26), and at least one 12 weight percent yttria-stabilized zirconia layer (30) disposed upon said at least one.segmented 7 weight percent yttria-stabilized zirconia layer (28).