Multi-Layer Abradable Coating for Gas Turbine Outer Airseal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines face performance issues due to heat transfer and erosion problems in outer airseals, particularly in downstream compressor stages where abradable coatings on nickel-based superalloy substrates are prone to degradation, leading to gas leakage and efficiency reduction.
Innovation Solution
A multi-layered abradable coating system is applied to the inner diameter surface of the outer airseal, comprising a metallic matrix with a thin, erosion-resistant top layer and a more abradable bottom layer, optimized for thermal spray deposition with varying porosity and composition to accommodate both normal and abnormal operational conditions, including a bondcoat and specific filler materials like boron nitride and bentonite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer abradable coating is applied to the outer airseal, then the coating provides initial protection and erosion resistance, but it cannot simultaneously accommodate both blade tip penetration during normal operation and abnormal erosion conditions
Solution Approach 1:
The coating system is divided into multiple layers with distinct functions: a hard, erosion-resistant top layer for abnormal conditions and a soft, abradable bottom layer for normal operation. This segmentation allows each layer to specialize in different operational scenarios, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The invention uses composite material structure combining dissimilar materials - a ceramic-based hard coating layer over a metallic abradable layer. This composite approach enables the coating system to exhibit both erosion resistance and controlled abradability, accommodating different operational conditions simultaneously.
2Ease of operation
If the abradable coating is made softer to allow blade tip penetration, then clearance maintenance is improved, but erosion resistance deteriorates
Solution Approach 1:
The coating is segmented into functional layers where the bottom layer provides softness for blade tip penetration and clearance maintenance, while the top layer provides hardness for erosion resistance. This resolves the contradiction by distributing different mechanical properties to different layers.
Solution Approach 2:
Different regions of the coating system have different local properties - the bottom layer is locally optimized for abradability while the top layer is locally optimized for erosion resistance. This local quality differentiation allows the system to satisfy conflicting requirements in different zones.
3Strength
If the abradable coating is made harder to resist erosion, then erosion resistance is improved, but blade tip penetration and clearance adaptation deteriorate
Solution Approach 1:
The coating system segments erosion resistance and abradability functions into separate layers, allowing the top layer to be hard for erosion resistance while the bottom layer remains soft for blade tip penetration and clearance adaptation.
Solution Approach 2:
The composite structure combines a hard ceramic-based top layer for erosion resistance with a soft metallic bottom layer for abradability. This material combination resolves the contradiction by allowing each material to excel at its designated function.
4Reliability
If a multi-layer coating system is implemented, then both erosion resistance and abradability are achieved, but manufacturing complexity increases
Solution Approach 1:
While segmentation into multiple layers increases structural complexity, it enables the coating system to achieve reliable performance under both normal and abnormal conditions. The segmentation is necessary to resolve the fundamental contradiction between abradability and erosion resistance.
Solution Approach 2:
The composite material system, while structurally more complex than a single-layer coating, provides superior and reliable performance by combining materials with complementary properties. The complexity is justified by the significant improvement in reliability and adaptability.
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 effectively manages heat transfer and blade tip penetration, maintaining clearance and reducing erosion, thereby enhancing gas turbine engine performance and efficiency by allowing for controlled wear and adaptation to operational imbalances.
Implementation Method 1
The method comprises thermal spray of the first layer and the second layer
Implementation Method 2
The first layer has at most 10% porosity and the second layer has at least 40% porosity
Data Source
Figure 1
Figure 2
Figure 2A~2B
AI summary
A blade outer airseal has a body comprising: an inner diameter (ID) surface; an outer diameter (OD) surface; a leading end; and a trailing end. The airseal body has a metallic substrate and a coating system atop the substrate along at least a portion of the inner diameter surface. At least over a first area of the inner diameter surface, the coating system comprises an abradable layer system comprising a plurality of layers including a relatively erosion-resistant first layer atop a relatively abradable second layer.