Machinable Coating for Gas Turbine Seal Slot Surface Finish
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Solution Overview
Problem
Gas turbine engine seals, particularly those made of ceramic matrix composites, face challenges with surface roughness and sealing efficiency due to imperfections in slot formation and material properties, leading to reduced thermal compatibility and wear resistance.
Innovation Solution
A method involving the application of a machinable coating, such as rare earth silicates or alumina-stabilized zirconia, to seal slots in engine components, followed by machining to achieve a smooth surface roughness of less than 100 ra (2.54 µm) and an open width of at least 20 mils (0.51 mm), enhancing thermal resistance and wear characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a slot is formed in a component to receive a seal, then the seal can be installed, but the surface roughness is too high (greater than 100 ra) causing poor sealing efficiency
Solution Approach 1:
A coating is applied to the slot before the seal is installed. This preliminary coating action allows the slot to be formed with standard manufacturing methods while the coating subsequently provides the required smooth surface finish (less than 100 ra) that enables proper seal function.
Solution Approach 2:
A coating material serves as an intermediary between the rough slot surface and the seal. The coating fills in surface irregularities and provides a smooth intermediate surface that allows the seal to function properly even when the underlying slot has high roughness from standard manufacturing processes.
2Reliability
If the slot open width is made small to improve sealing, then sealing efficiency improves, but the seal cannot be properly installed or accommodated
Solution Approach 1:
The coating changes the effective parameters of the slot surface by providing a smooth finish (reducing surface roughness to less than 100 ra) while allowing the slot open width to be larger than previously possible. This parameter transformation enables both adequate width for seal installation and high sealing efficiency.
3Manufacturing precision
If a coating is applied to the slot and then machined to achieve smooth surface, then surface roughness is reduced (less than 100 ra), but additional manufacturing steps are required
Solution Approach 1:
Instead of using complex mechanical machining processes to achieve the required surface roughness of less than 100 ra, the patent applies a coating that inherently provides the smooth surface finish. This substitutes a chemical/coating process for what would otherwise require complex mechanical machining operations.
Data Source
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AI summary
A method of coating a seal slot (106a; 106b) according to an exemplary embodiment of this disclosure, among other possible things includes applying a coating (200) to a slot (106a; 106b) in a component (102; 104) and machining the coating (200) to provide an open width configured to receive a seal (100). after the applying, the slot (106a; 106b) has an initial open width (O) that is smaller than the open width after the machining. A method of forming a sealing assembly is also disclosed.