Ceramic Abradable Coating for Uniform Abradability
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Solution Overview
Problem
Existing abradable coatings in turbomachinery suffer from variability in deposition due to stochastic processes, leading to inconsistent abradability and increased frictional heating, which can damage blade tips and reduce engine efficiency.
Innovation Solution
A ceramic matrix layer with controlled micro-hardness and porosity, applied on a bond coat layer, is used to create an abradable coating with tailored hardness and abradability, manufactured through a controlled process involving a hydroxide solution treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If air plasma spray is used to deposit metallic and/or ceramic matrix with dislocators and porosity, then abradability is provided, but local variations of abradability and other properties occur throughout the coating due to stochastic deposition
Solution Approach 1:
The patent applies a post-deposition heat treatment process that transforms the coating properties by changing parameters such as temperature, time, and atmospheric conditions. This heat treatment modifies the microstructure, porosity distribution, and hardness of the coating, converting stochastic variations into controlled, uniform properties while preserving the desired abradability characteristics.
Solution Approach 2:
The patent creates a composite structure by combining the as-sprayed coating material with controlled porosity and dislocators, then transforming it through heat treatment into a composite material system where the treated matrix exhibits enhanced uniformity. The combination of metallic/ceramic matrix with controlled porosity creates a composite that achieves both abradability and uniformity.
2Loss of energy
If blade tip clearance is minimized to maximize engine efficiency, then leakage is reduced, but periodic contact between blade tips and seal occurs during operation
Solution Approach 1:
The patent applies an abradable coating to the seal surface that is designed to be sacrificial - it wears away preferentially during periodic blade tip contact, protecting the more valuable blade tips from damage. The coating acts as a disposable protective layer that can be replaced or reformed, while the blade tips remain intact for continued use.
Solution Approach 2:
The patent utilizes a porous coating structure with controlled porosity (5-50%) that provides abradability. The porous nature allows the coating to be easily removed by blade tip contact while maintaining seal functionality. The porosity enables the material to be cut and abraded preferentially, creating a protective mechanism for the blade tips.
3Object-affected harmful factors
If abradable coating is applied to seal to protect blade tips, then blade tip damage is prevented, but frictional heating increases during contact
Solution Approach 1:
The patent applies heat treatment to modify the coating's physical and chemical parameters, including hardness, porosity, and thermal properties. This treatment optimizes the balance between abradability and frictional heating by creating a microstructure that controls heat generation and dissipation during blade tip contact, reducing excessive temperature rise while maintaining protective functionality.
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 effectively reduces blade tip wear and frictional heating by ensuring consistent abradability, enhancing engine performance and safety.
Implementation Method 1
soaking the as-coated component in a hydroxide solution to convert the first coating into the abradable coating
Implementation Method 2
a ceramic matrix layer with controlled micro-hardness and porosity
Implementation Method 3
reduces blade tip wear and frictional heating by ensuring consistent abradability
Data Source
Figure 1
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AI summary
An abradable coating (60) comprising a ceramic matrix layer (64) disposed on a bond coat layer (62), wherein the abradable coating (60) has a micro-hardness of 35 to 60 as measured on the Rockwell HRC hardness scale in accordance with ASTM E18.