Airfoil Coating System with Localized Platinum-Group Metal Layers
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Solution Overview
Problem
Current protective coatings for aircraft gas turbine components fail to adequately extend operating service temperatures and lives due to issues like low-cycle fatigue, particularly in high-temperature applications.
Innovation Solution
A method involving the formation of a platinum-group metal layer on the trailing edge and an aluminide coating on the leading, trailing, pressure, and suction sides of airfoil components, with an optional thermal barrier coating, to enhance durability and resistance to fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform platinum-group metal aluminide coating is applied to the entire airfoil surface, then corrosion and oxidation resistance is improved, but manufacturing cost increases due to excessive use of expensive platinum-group metals
Solution Approach 1:
The patent applies different coating compositions to different regions of the airfoil based on their specific service conditions. Platinum-group metal aluminide coating is applied only to the trailing edge where it provides the most benefit, while other regions receive alternative coatings or no coating, optimizing both performance and cost.
Solution Approach 2:
The airfoil surface is divided into distinct zones (trailing edge, leading edge, mid-section) that receive different coating treatments. This segmentation allows targeted application of expensive platinum-group metals only where most needed, rather than uniform coverage across the entire surface.
2Temperature
If protective coatings are applied to extend operating service temperatures, then temperature resistance is improved, but susceptibility to low-cycle fatigue increases due to coating brittleness
Solution Approach 1:
The patent uses composite coating systems combining multiple materials with complementary properties. The platinum-group metal aluminide is combined with other coating materials that provide flexibility and fatigue resistance, creating a composite structure that withstands both high temperatures and cyclic mechanical loading.
Solution Approach 2:
The coating composition and microstructure are optimized by controlling processing parameters to achieve a balance between temperature resistance and mechanical flexibility. Adjusting alloying elements and heat treatment parameters modifies the coating's physical properties to reduce brittleness while maintaining high-temperature protection.
3Use of energy by moving object
If the turbine operating temperature is increased to improve efficiency, then energy conversion efficiency is improved, but material durability deteriorates due to thermal stress and oxidation
Solution Approach 1:
The patent applies sacrificial protective coatings that can be readily replaced. These coatings protect the expensive turbine airfoil from direct exposure to harsh high-temperature environments, allowing the base material to operate at higher temperatures while the coating absorbs the environmental damage and can be renewed when worn.
Solution Approach 2:
Protective coatings serve as intermediary layers between the turbine airfoil material and the harsh combustion environment. These intermediate layers shield the base metal from direct thermal stress and oxidation, enabling higher operating temperatures without compromising material durability.
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 susceptibility to property degradation such as low-cycle fatigue failures while conserving expensive platinum-group metals and maintaining the benefits of existing protective coatings, allowing for optimized performance across the component surface.
Implementation Method 1
plating the unmasked area with a platinum-group metal
Implementation Method 2
Among the currently known diffusional protective layers are aluminide and platinum aluminide layers
Implementation Method 3
The ceramic thermal barrier coating layer insulates the component from the exhaust gas
Data Source
AI summary
A method for forming a coating on a surface of an airfoil is provided, where the airfoil has a leading edge, a trailing edge, a pressure side, and a suction side. The method can include forming a platinum-group metal layer on the surface of the airfoil along at least a portion of the trailing edge, and forming an aluminide coating over the surface of the airfoil of the leading edge, the trailing edge, the pressure side, and the suction side. The leading edge may be substantially free from any platinum-group metal. The method may further include, prior to forming the aluminide coating, forming a bond coating on the surface of the airfoil along the leading edge, and after forming the aluminide coating, forming a thermal barrier coating over the bond coating. A method is also generally provided for repairing a coating on a surface of an airfoil.