Coating Removal Sequence for Complete Stripping Without Component Damage
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Solution Overview
Problem
Existing methods for removing coating systems from components, such as gas turbine engine parts, often result in partial removal or damage, necessitating costly repairs or scrapping, and there is a need for a more effective and efficient method to restore components to meet strict conformance standards.
Innovation Solution
A method involving immersion in caustic solutions, water jet blasting, acid stripping, aluminising, and ultra-high pressure water jetting to entirely remove the coating system, including bond and ceramic layers, while minimizing damage to the component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coating removal methods are used, then coating system can be removed, but the component is damaged in the process
Solution Approach 1:
The coating removal process is divided into multiple sequential stages: initial chemical etching to loosen coating bonds, followed by controlled mechanical removal, and final precision finishing. This segmentation allows each stage to address specific aspects of coating removal without applying excessive force that could damage the component
Solution Approach 2:
Chemical agents are used as intermediaries to facilitate coating removal. The chemical etchants selectively break down the coating material and its bonding to the substrate, enabling mechanical removal processes to proceed with minimal force and reduced risk of component damage
2Manufacturing precision
If partial coating removal is performed, then some coating remains on the component, but further treatment with more potent agents increases damage risk
Solution Approach 1:
Milder chemical etching and mechanical processes are applied first to remove the majority of the coating system. This preliminary action reduces the coating thickness to a manageable level, allowing subsequent precision steps to achieve complete removal without requiring aggressive treatments that could damage the component
3Manufacturing precision
If component is damaged during coating removal, then component must be repaired or scrapped, but repair costs significant effort and may require scrapping
Solution Approach 1:
The multi-stage controlled removal process incorporates buffer zones and monitoring points where process parameters can be adjusted to prevent damage before it occurs. Protective measures are built into each stage to cushion against potential harm to the component, ensuring it remains repairable or reusable
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 allows for complete removal of the coating system without damaging the component, facilitating subsequent repair and adherence to strict standards, reducing scrap rates and resource consumption.
Implementation Method 1
immersing the component in a caustic solution of 46 to 54% potassium hydroxide or 46 to 54% sodium hydroxide; maintaining the component in the caustic solution at atmospheric pressure for a time equal to or less than one and a half hours at a temperature equal to or greater than 150° C. and equal to or less than 250° C.
Implementation Method 2
immersing the component in a caustic solution of 46 to 54% potassium hydroxide or 46 to 54% sodium hydroxide; maintaining the component in the caustic solution at atmospheric pressure for a time equal to or less than one and a half hours at a temperature equal to or greater than 150° C. and equal to or less than 250° C.
Implementation Method 3
water jet blasting the component by directing water at the ceramic top coat layer from a nozzle at a pressure of 275 to 296 MPa (40,000 to 43,000 psi), arranging the nozzle at a stand-off distance from the ceramic coating of 25 to 40 mm and traversing the nozzle over the ceramic top coat layer at a speed of 4 to 8 mm per second to remove the ceramic top coat layer and any thermally-grown oxide
Implementation Method 4
immersing the component in an acid solution; immersing the component in a solution of nitric acid and/or sulphamic acid
Implementation Method 5
ultra-high pressure water jetting the component to remove any Pt—Al formed in step (h)
Implementation Method 6
aluminising the component to convert any diffused Pt within the bond coat layer to Pt—Al
Implementation Method 7
aluminising the component to convert any diffused Pt within the bond coat layer to Pt—Al
Data Source
AI summary
A method of removing a coating system from a component that is coated with the coating system. The method involves: (a) immersing the component in a caustic solution; (b) maintaining the component in the caustic solution at atmospheric pressure for a time ≤1.5 hours at a temperature ≥150° C. and ≤250° C.; (c) removing the component; (d) rinsing the component in water; (e) water jet blasting the component to remove the ceramic top coat layer and any thermally-grown oxide; (f) immersing the component in an acid solution; (g) ultra-high pressure water jetting the component; (h) aluminising the component to convert any diffused Pt within the bond coat layer to Pt—Al; (i) acid stripping and grit blasting the component; (j) immersing the component in a solution of nitric acid and/or sulphamic acid; and (k) ultra-high pressure water jetting the component to remove any Pt—Al.