Segmented Ceramic Interlayer Coating for Turbine Spallation Resistance
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Solution Overview
Problem
Conventional protective coatings for high-temperature components in gas turbine engines suffer from erosion and spallation due to internal stresses, leading to the need for frequent replacement or refurbishment, and there is a lack of easy-to-use, thermally insulating coatings with improved erosion resistance.
Innovation Solution
A segmented ceramic topcoat with a ceramic interlayer and optional erosion-resistant thermal barrier coating is applied, featuring a toughened ceramic interlayer composed of yttria stabilized zirconia or other oxide ceramics, which is disposed between the topcoat and the substrate, enhancing erosion resistance and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional protective coating is applied to high-temperature components, then the component is protected from erosion and oxidation, but internal stresses develop in the coating making it vulnerable to erosion and spalling
Solution Approach 1:
The coating system is divided into multiple functional layers: a bond coat layer, a ceramic interlayer, and a topcoat layer. This segmentation allows each layer to perform its specific function - the bond coat provides oxidation resistance, the interlayer manages thermal stress, and the topcoat provides thermal insulation and erosion resistance, thereby resolving the spalling vulnerability of conventional single-layer coatings
Solution Approach 2:
The coating system uses composite material structure combining different ceramic materials and metal alloys in distinct layers. The interlayer uses materials with intermediate thermal expansion properties between the substrate and topcoat, creating a composite structure that reduces internal stresses while maintaining protective functions
2Temperature
If a thick ceramic topcoat is applied to provide thermal insulation, then thermal stability is improved, but the coating becomes more vulnerable to erosion and crack propagation
Solution Approach 1:
The thick ceramic topcoat is segmented into smaller sections by control cracks that extend from the substrate through the topcoat but are arrested at the interlayer. This segmentation prevents continuous crack propagation across the entire coating thickness, allowing the topcoat to maintain its thermal insulation function while improving erosion resistance
Solution Approach 2:
The ceramic interlayer acts as an intermediary between the substrate and the thick topcoat. It provides a transition zone that manages thermal stress and arrests crack propagation, enabling the topcoat to be thicker for better thermal insulation without proportionally increasing vulnerability to erosion and crack propagation
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 provides improved erosion resistance and thermal stability, delaying crack initiation and propagation, maintaining stable tip clearance, and enhancing the durability of components in gas turbine engines.
Implementation Method 1
delaying crack initiation and propagation
Implementation Method 2
thermally insulating coatings
Data Source
AI summary
A turbine article includes a substrate with a geometric surface feature having a plurality of recesses recessed into the substrate. A ceramic topcoat is disposed over the geometric surface feature. The topcoat includes portions that are separated by faults extending through the topcoat from the geometric surface feature so the topcoat is segmented. A ceramic interlayer is disposed between the topcoat and the geometric surface feature.