Nitride-Free Vapor Deposited Chromium Coating for Turbine Airfoils
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Solution Overview
Problem
Existing methods for applying chromium diffusion coatings to substrates, such as gas turbine engine components, often result in nitride deposition, which compromises corrosion protection and requires damaging removal processes.
Innovation Solution
A method involving a nitrogen-free chromium layer application using a mixture of chromium, chromium III or II chloride, and a carrier material, heated in an enclosed space to generate gaseous chromium, ensuring diffusion into nickel-based superalloys without nitride formation, with controlled ratios and temperatures to prevent nitride deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vapor deposition techniques are used to apply chromium coating, then chromium layer can be deposited on substrate, but nitrides are formed which compromise corrosion protection
Solution Approach 1:
The patent changes the chemical composition parameters of the vapor phase by using a chromium-containing compound (such as chromium acetylacetonate) instead of conventional chromium sources, and controls the partial pressure ratios of chromium to nitrogen to prevent nitride formation while maintaining effective chromium deposition for corrosion protection
Solution Approach 2:
The patent creates a nitrogen-free or low-nitrogen atmosphere during deposition by using organic carrier gases and controlling the vapor phase composition, thereby preventing nitride formation while still achieving effective chromium diffusion coating on the substrate
2Reliability
If nitride layer is removed from substrate, then corrosion protection is improved, but substrate is damaged by removal processes
Solution Approach 1:
The patent prevents nitride formation in the first place by controlling the deposition atmosphere and chemical composition, eliminating the need for subsequent nitride removal processes that would damage the substrate. This preliminary prevention avoids the harmful effects of mechanical or chemical removal methods
3Manufacturing precision
If chromium to activator ratio is increased, then chromium layer quality improves, but process complexity increases
Solution Approach 1:
The patent optimizes the chromium to activator ratio within a specific range (120:1 to 160:1) to achieve high-quality chromium diffusion coatings. This parameter optimization balances coating quality with process simplicity, avoiding the need for overly complex control systems while ensuring consistent, high-performance results
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 method effectively applies a chromium layer without nitrides, enhancing corrosion protection and minimizing substrate damage, thereby improving the durability and reliability of coated components.
Implementation Method 1
a vapor comprising a gaseous chromium wherein the gaseous chromium is generated from a mixture consisting essentially of chromium, an activator selected from the group consisting of chromium III chloride and chromium II chloride, and a carrier material, wherein the gaseous chromium is generated from a mixture consisting essentially of chromium, an activator selected from the group consisting of chromium III chloride and chromium II chloride, and a carrier material, wherein the ratio of chromium to activator is between 120:1 and 160:1
Implementation Method 2
the chromium diffuses into the portion of the substrate to define the chromium layer
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A process for applying a chromium layer on a substrate, specifically a turbine engine airfoil, by contacting at least a portion of the substrate with a gaseous chromium wherein the gaseous chromium is generated from a substantially nitrogen free source.