Abradable Coating Repair via Selective Blasting and Thermal Spraying
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Solution Overview
Problem
Current methods for repairing abradable material coatings on steam turbine stationary components are time-consuming and expensive, as they require complete removal and reapplication of the coating, which can't effectively close gaps caused by wear, leading to steam leakage and performance degradation.
Innovation Solution
A method where a portion of the used abradable material coating is removed by particle blasting, leaving a substantial portion intact, and a new abradable material layer is thermally sprayed on top, creating a thicker combined coating that closes gaps between sealing surfaces without disassembling the turbine, using a bond layer and abradable material like nickel-chromium-iron-aluminum hexagonal boron nitride powder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the abradable material coating is completely removed and reformed using conventional methods, then the coating is restored to its initial state, but the process is time-consuming, expensive, and cannot effectively close gaps caused by wear
Solution Approach 1:
The patent extracts and removes only the worn or damaged portions of the abradable material coating using abrasive blasting, rather than completely removing the entire coating. This selective removal approach reduces repair time and cost while maintaining sealing effectiveness by preserving the majority of the intact coating.
Solution Approach 2:
Instead of removing the coating and starting over with a complete reapplication process, the invention inverts the approach by building up the coating selectively only where needed. The abradable material is applied only to areas where the coating has worn away, rather than reforming the entire coating surface.
2Manufacturing precision
If the abradable material coating is completely removed and reformed, then the coating is restored, but the underlying metal sealing surface is exposed and the new coating is applied only on the bond layer, not over previous abradable material, resulting in gaps that don't close with worn teeth
Solution Approach 1:
The patent applies different treatment to different areas of the coating surface. Intact portions of the abradable material coating are preserved, while only worn areas are removed and recoated. This localized approach maintains the original coating thickness in good areas while restoring thickness only where wear has occurred, ensuring proper sealing gap closure.
Solution Approach 2:
The invention applies partial action by removing only the necessary minimum amount of material to expose the bond layer in worn areas, rather than completely removing the entire coating. This partial removal and selective reapplication ensures the new abradable material is applied over both the bond layer and remaining intact abradable material, creating a seamless restored surface that properly closes sealing gaps.
3Ease of manufacture
If the component is removed from the steam turbine for complete coating removal and reformation, then the coating can be refurbished, but the process becomes expensive and requires disassembly and reassembly
Solution Approach 1:
The patent enables the coating refurbishment process to be performed in-situ on the steam turbine without requiring removal of the stationary component from the turbine assembly. The abrasive blasting and thermal spraying equipment can be positioned to treat the coating directly on the installed component, eliminating disassembly requirements and reducing complexity.
Solution Approach 2:
The refurbishment process is segmented into localized treatment zones rather than requiring complete disassembly. Only specific worn areas of the coating are treated, allowing the component to remain assembled in the turbine while targeting specific regions for repair, thus avoiding the need for full disassembly and reassembly operations.
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 restores the sealing surfaces to nominal dimensions, reduces steam leakage, and maintains performance without the need for complete refurbishment or disassembly, lowering costs and risks associated with reassembly.
Implementation Method 1
a bond layer and an abradable material layer over the bond layer
Implementation Method 2
a new abradable material layer is thermally sprayed on top
Implementation Method 3
a portion of the abradable material coating is removed by particle blasting
Data Source
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AI summary
The present invention is related to a method for repairing worn-out abradable coatings of gas turbine engine sealing components, wherein in a first step only a portion of the worn-out abradable material layer (164) is removed from a substrate (54,58) of a first component (22,40), which sealingly moves relative to another component in an operative state, e.g. blade tip and blade outer air seal. After having removed only parts of the worn-out abradable layer (164) a new abradable layer (180) is deposited by thermal spraying on the used abradable material layer (164), rather than completely removing the used abradable material and starting over on bare metal. Thus, a non-uniform worn-out abradable layer (164) is coated with a new abradable layer (180) such that a uniform layer thickness is achieved. Thereby sealing properties can be restored without excessive repairing costs.