Honeycomb Seal Diffusion Aluminide Coating Method
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Solution Overview
Problem
Honeycomb seals in gas turbines face oxidation and corrosion issues due to high temperatures, leading to a short lifespan, and existing slurry coating processes struggle with uniformity and complexity, especially when applied to internal and external surfaces with complicated geometries.
Innovation Solution
A method involving a gel aluminum-containing slurry with a halide activator and organic polymer binder is used to form a diffusion aluminide coating on honeycomb seals, which can be applied uniformly over a broad range of temperatures, followed by brazing to a substrate, ensuring a stable and durable aluminide coating with optional thermal barrier coating for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional slurry coating processes are used on honeycomb seals, then coating can be applied to internal and external surfaces, but the coating uniformity and process complexity deteriorate when applied to surfaces with complicated geometries
Solution Approach 1:
The invention changes the chemical parameters of the slurry composition by incorporating specific organic polymer binders and halide activators, which enable the coating material to flow uniformly into complex geometries and internal passages while maintaining consistent coating thickness through controlled chemical reactions during the diffusion process
Solution Approach 2:
The organic polymer binder acts as an intermediary carrier that transports the aluminum coating material uniformly across complex surfaces, allowing the slurry to penetrate internal passages and coat difficult-to-reach areas while maintaining coating uniformity through the binder's flow properties and adhesion characteristics
2Reliability
If higher processing temperatures are used to form outward-type diffusion coatings, then oxidation and low-cycle fatigue resistance improve, but the processing complexity and energy consumption increase
Solution Approach 1:
The invention utilizes phase transitions of the halide activator and organic binder during controlled heating, where the halide activator volatilizes at specific temperature ranges to promote aluminum diffusion, and the organic binder decomposes and burns off, enabling the formation of outward-type diffusion coatings with improved oxidation and fatigue resistance through controlled phase changes rather than continuous high-temperature processing
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 method produces a uniformly thick diffusion aluminide coating that extends the lifespan of honeycomb seals by preventing oxidation and corrosion, with the ability to handle complex geometries and internal surfaces effectively, and allows for the production of both inward and outward-type coatings, improving oxidation and low-cycle fatigue resistance.
Implementation Method 1
react the activator with the metallic aluminum to form the halide vapor, react the halide vapor at the substrate surfaces to deposit aluminum on the surfaces of the seal
Implementation Method 2
diffuse the deposited aluminum into the surfaces to form a diffusion aluminide coating
Implementation Method 3
heating the component to a temperature sufficient to remove or burn off the binder
Implementation Method 4
heating the braze material, seal substrate and coated cellular seal sufficiently to form a braze joint
Implementation Method 5
brazing the coated cellular seal to a seal substrate to form the cellular seal member
Implementation Method 6
aluminum-containing coatings form a protective aluminum oxide (alumina) scale or layer that inhibits corrosion and oxidation of the coating and the underlying substrate
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3
AI summary
A method (100) for making a cellular seal member for a turbine is disclosed. The method includes, in sequence, forming (110) a diffusion aluminide coating on a surface of a cellular seal to form a coated cellular seal. The method also includes brazing (120) the coated cellular seal (10) to a seal substrate (50).