Chromium-Enriched Diffused Aluminide Coating for Gas Turbines
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Solution Overview
Problem
Existing chromium-enriched metallic coatings for gas turbine engine components do not effectively enhance corrosion resistance, particularly in severe environments, as they lack a stable and efficient method for replacing aluminum with chromium to form a protective layer.
Innovation Solution
A method involving chemical vapor deposition of aluminum followed by chromium deposition, using a halide activator to replace a portion of the aluminum with chromium, resulting in a chromium-enriched coating with specific compositional and structural characteristics, including a chromium layer with 20-40% chromium by weight and an aluminum diffusion zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium is deposited to enhance corrosion resistance, then corrosion protection is improved, but the coating structure becomes unstable and ineffective in severe environments
Solution Approach 1:
The patent applies local quality by creating a non-uniform chromium distribution within the aluminum coating. The chromium concentration varies through the coating thickness, with higher chromium content (20-40% by weight) in the outer 30-60% of the coating thickness and lower chromium content in the inner regions. This gradient structure provides optimal corrosion resistance at the surface while maintaining stability at the substrate interface, resolving the contradiction between corrosion protection and structural stability.
2Reliability
If aluminum is replaced with chromium using conventional methods, then chromium layer formation is attempted, but the replacement process is inefficient and produces unstable coatings
Solution Approach 1:
The patent employs parameter changes by utilizing a halide activator (such as ammonium fluoride, ammonium chloride, or chromium chloride) to modify the chemical reactivity parameters during chromium deposition. The activator facilitates the replacement of aluminum with chromium through chemical reactions, enabling efficient chromium incorporation at temperatures of 1900-2100°F. This chemical activation mechanism dramatically improves chromium replacement efficiency compared to conventional physical vapor deposition methods.
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 provides a robust and corrosion-resistant chromium-enriched coating that effectively replaces aluminum, enhancing the durability and protection of gas turbine engine components by forming a stable chromium layer with improved corrosion resistance.
Implementation Method 1
at least one of the aluminum and the chromium are deposited by chemical vapor deposition
Implementation Method 2
the chromium replaces at least a portion of the aluminum
Data Source
AI summary
A method of applying a protective coating to an article comprises the steps of a) depositing aluminum in a surface region of an article, and b) depositing chromium is the surface region of the article subsequent to step a), whereby at least a portion of the chromium replaces at least a portion of the aluminum. Another method and an article are also disclosed.