Airfoil Internal Coating via Electrolytic Deposition
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Solution Overview
Problem
The internal surface of airfoil components in gas turbine engines is susceptible to high-temperature oxidation and corrosion due to line-of-sight limitations of traditional coating techniques, leading to performance deterioration and material damage, especially in environments with high SO2 concentrations.
Innovation Solution
A method involving electrolytic deposition of a chromium or aluminum alloy layer on the internal surface of airfoils, followed by heat treatment to form a thermally grown oxide layer and aluminide diffusion layer, enhancing hot corrosion resistance and accessibility through conforming electrodes and electroless deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional coating techniques (plasma spray, cathodic arc, electron beam) are used on internal surfaces, then coating application is straightforward on accessible surfaces, but line of sight limitation prevents effective coating of internal passages
Solution Approach 1:
The patent replaces traditional mechanical coating methods (plasma spray, cathodic arc, electron beam) with an electrolytic deposition process. This chemical/electrochemical approach allows coating material to be deposited through the electrolyte solution that fills the internal passages, eliminating the line-of-sight limitations that constrain mechanical coating methods.
Solution Approach 2:
The patent uses an electrolyte solution (liquid medium) to deliver coating material to internal surfaces. The electrolyte flows through or fills the internal passages, enabling material deposition in geometries inaccessible to traditional spray or vapor-based methods that require direct line of sight.
2Device complexity
If internal surfaces are left uncoated, then manufacturing complexity is reduced, but high temperature oxidation and corrosion cause performance deterioration and material damage
Solution Approach 1:
The electrolytic deposition process automatically deposits coating material on all surfaces accessible to the electrolyte solution, including complex internal passages. The electrical current and electrolyte flow naturally follow the geometry of the internal surfaces, providing self-adapting coverage without requiring complex positioning or masking systems.
Solution Approach 2:
The patent applies controlled electrolytic deposition parameters (current density, electrolyte composition, deposition time) to achieve appropriate coating thickness and composition on internal surfaces. By adjusting these parameters, the process forms protective layers with specific properties tailored for high-temperature oxidation and corrosion resistance.
3Reliability
If thicker coating layers are applied to improve protection, then corrosion resistance increases, but coating material consumption and processing time increase
Solution Approach 1:
The electrolytic deposition process enables different coating thicknesses and compositions at different locations within the internal passages. Areas requiring higher protection can receive thicker or more corrosion-resistant coatings, while less critical areas receive thinner coatings, optimizing material usage based on local requirements.
Solution Approach 2:
The patent applies coating material through electrolytic deposition until the desired protective thickness is achieved, potentially using slightly more material than the minimum theoretical requirement to ensure complete coverage and adequate protection, particularly in complex geometries where uniform deposition is challenging.
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 effectively forms a protective alumina and chromium oxide layer that increases the life cycle of airfoil components by reducing substrate element diffusion and maintaining high-temperature resistance, thus reducing maintenance and repair needs.
Implementation Method 1
electrolytically applying a first layer that comprises chromium or a chromium alloy onto a surface of the internal passage; electrolytically applying a second layer comprising aluminum or an aluminum alloy onto the first layer
Implementation Method 2
heat treating the article to promote interdiffusion between the first layer and the second layer
Implementation Method 3
the heat treating results in the formation of a layer of thermally grown oxides that comprise alumina and chromium oxide
Data Source
AI summary
Disclosed herein is a method of coating, comprising providing an article having an internal passage therein to be coated; electrolytically applying a first layer that comprises chromium or a chromium alloy onto a surface of the internal passage; electrolytically applying a second layer comprising aluminum or an aluminum alloy onto the first layer; and heat treating the article to promote interdiffusion between the first layer and the second layer.