Bond Coat Summit Area Assessment for Ceramic Coating Adhesion
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Solution Overview
Problem
Current methods for forming bond coats for ceramic coatings on metallic substrates lack a comprehensive approach to quantify and optimize the surface topography, leading to inconsistent spallation lifetimes and thermal barrier performance in high-temperature applications like gas turbine engines.
Innovation Solution
A method to assess and optimize bond coat quality by determining the thresholded summit area (Ssth) using a novel surface topography parameter, which characterizes the thermo-mechanically dominant summits and their impact on ceramic coating adhesion and durability, employing thermal spraying processes like APS, HVOF, and VPS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional surface roughness parameters (Ra, Sa) are used to characterize bond coat topography, then measurement and assessment can be performed, but the parameters fail to accurately predict spallation lifetime and adhesion quality
Solution Approach 1:
The patent changes the surface topography parameters from conventional Ra/Sa to a novel set of parameters including thresholded summit area (Ssth), summit density (Sds), and curvature radius (Rc). These new parameters specifically characterize the thermo-mechanically dominant summits that control adhesion and spallation behavior, enabling accurate prediction of coating lifetime while maintaining measurement feasibility.
2Ease of manufacture
If thermal spraying processes are used to apply bond coats, then coating can be deposited on metallic substrates, but inconsistent surface topography results in variable adhesion quality and spallation resistance
Solution Approach 1:
The patent implements a feedback mechanism where the surface topography is measured after bond coat deposition, characterized using the novel parameters (Ssth, Sds, Rc), and this information is used to optimize subsequent coating processes. This closed-loop approach ensures consistent adhesion quality and spallation resistance while maintaining the ease of thermal spraying manufacturing.
3Productivity
If the bond coat surface topography is not optimized, then coating application can proceed without additional characterization, but adhesion between ceramic layer and substrate deteriorates under thermal cycling
Solution Approach 1:
The patent applies preliminary action by characterizing and optimizing the bond coat surface topography before applying the ceramic layer. The novel parameters (especially Ssth and Rc) guide the creation of an optimal surface morphology that enhances adhesion, ensuring the bond coat is properly prepared to withstand thermal cycling before the final coating is applied.
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 Ssth parameter effectively correlates with spallation lifetime and thermal barrier performance, enabling the production of consistently high-performing ceramic coating systems with improved adhesion and durability, even under varying thermal cycling conditions, thereby enhancing the temperature capability and durability of components like those in gas turbine engines.
Implementation Method 1
the bond coat is applied to the metallic substrate using one or more thermal spraying process, such as air plasma spraying (APS); high velocity oxygen fuel thermal spraying (HVOF); high velocity air fuel spraying (HVAF); low pressure plasma spraying (LPPS)/vacuum plasma spraying (VPS); or cold spraying
Data Source
AI summary
A method of assessing the quality of a bond coat for bonding a ceramic coating to a metallic substrate comprises determining a thresholded summit area for the bond coat.