Diffusion-Coated Turbine Component Cleaning Without Diffusion Zone Loss
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Solution Overview
Problem
Current methods for removing diffusion aluminide coatings from gas turbine engine components often result in substrate alloy depletion and altered airflow characteristics, leading to component scrapping, as they involve complete removal of the coating, including the diffusion zone, using harsh chemicals and mechanical processes.
Innovation Solution
A method using laser beam pulses to selectively remove contaminants and portions of the additive layer without damaging the diffusion zone, allowing for rejuvenation and repair of the coating, including the application of a new aluminide coating and diffusion heat treatment to maintain the original chemistry and microstructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If complete removal of diffusion coating is performed using harsh chemicals and mechanical processes, then the coating is fully removed, but substrate alloy depletion and altered airflow characteristics occur leading to component scrapping
Solution Approach 1:
The patent extracts and removes only the contaminant layer from the diffusion coating surface using laser beam pulses, rather than removing the entire coating. This selective extraction preserves the intact diffusion zone and substrate, avoiding alloy depletion while eliminating contaminants to enable component repair and reuse
Solution Approach 2:
The laser beam pulses apply localized energy treatment only to the contaminant-containing outer layer of the coating. This local quality approach ensures that the diffusion zone and substrate remain unaffected, maintaining their original chemical composition and structural integrity while achieving contaminant removal
2Reliability
If laser beam pulses are used to selectively remove contaminants, then the diffusion zone is preserved, but additional processing steps are required
Solution Approach 1:
The patent combines the contaminant removal step with subsequent coating rejuvenation steps into an integrated repair process. The laser cleaning is immediately followed by re-aluminizing and heat treatment, merging multiple operations into a sequential workflow that preserves the substrate while restoring the protective coating functionality
Solution Approach 2:
The patent replaces traditional mechanical and chemical removal methods (grit blasting, acid stripping) with laser beam pulse technology. This substitution eliminates the need for harsh chemicals and mechanical abrasion that damage the substrate, using instead a controlled thermal field that selectively vaporizes contaminants while preserving the diffusion zone
3Ease of manufacture
If traditional removal methods are used, then the coating is completely removed, but time, labor, and cost increase
Solution Approach 1:
The patent applies partial action by removing only the necessary portion (contaminants) rather than the entire coating. The laser beam pulses are applied with controlled energy and duration to achieve just enough material removal to eliminate contaminants while preserving the diffusion zone, thereby reducing repair time and preserving valuable substrate material
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
This approach reduces time, labor, and cost for recoating, maintains dimensional and airflow requirements, and improves repair hardware yields by preserving the substrate and achieving a rejuvenated coating with the same chemistry and microstructure as the original, while consuming less wall thickness than full-stripping methods.
Implementation Method 1
subjecting the surface of the component containing contaminants to laser beam pulses to remove contaminants from the component
Implementation Method 2
During high temperature exposure in air, the MA1 intermetallic forms a protective aluminum oxide (alumina) scale or oxide layer that inhibits oxidation of the diffusion coating and the underlying substrate
Implementation Method 3
Diffusion processes generally entail reacting the surface of a component with an aluminum-containing gas composition to form two distinct zones
Data Source
AI summary
A method of removing contaminants from a surface of a gas turbine engine component protected by a diffusion coating that comprises an additive layer on the surface of the component and a diffusion zone in the surface of the component. The method includes subjecting the surface containing contaminants to laser beam pulses to remove contaminants from the component such that contaminants on the surface of the component are removed without damaging or removing the diffusion zone of the diffusion coating. Methods for controlled removal of at least a portion of a thickness of a diffusion coating from a coated superalloy component are also provided.