Thermal Barrier Coating Adhesion via Local Aluminium Enrichment
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Solution Overview
Problem
Existing methods for forming thermal barrier coatings, particularly those using low activity aluminizing processes, result in reduced surface roughness and adhesion between the bond coat and top coat, leading to decreased resistance to thermal fatigue and premature detachment of the top coat, which complicates the restoration process and increases production costs.
Innovation Solution
A method involving the application of fine aluminium powder with a specific size distribution (15-150 µm) on a temporary intermediate diffusion layer, followed by thermal treatment in a vacuum to enhance the surface roughness and adhesion between the bond coat and top coat, creating a stable and corrugated intermediate diffusion layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low activity aluminizing process is used to form intermediate diffusion layer, then oxidation resistance is improved, but surface roughness is reduced leading to poor adhesion
Solution Approach 1:
The invention applies different quality requirements to different regions of the intermediate diffusion layer. The bulk of the layer maintains low aluminium concentration for oxidation resistance, while the outer surface is selectively enriched with aluminium to create a rough, adherent morphology. This local differentiation resolves the contradiction between oxidation resistance and adhesion.
Solution Approach 2:
The invention changes the aluminium concentration parameter through a two-stage diffusion process. First, aluminium is diffused at lower concentration for oxidation resistance, then additional aluminium is applied and diffused to create surface enrichment. This parameter transformation enables both oxidation resistance and adhesion to be achieved.
2Use of energy by moving object
If high activity aluminizing process is used to increase surface roughness, then adhesion is improved, but oxidation resistance is reduced
Solution Approach 1:
The invention creates local quality differentiation within the intermediate diffusion layer. The inner region maintains properties for oxidation resistance while the outer region develops properties for adhesion. This spatial differentiation allows the coating to simultaneously achieve both protection modes without compromising either function.
Solution Approach 2:
The invention performs preliminary aluminium diffusion to establish oxidation resistance, then subsequently enriches the surface with additional aluminium to create adhesion. This sequential action ensures that oxidation resistance is established before adhesion enhancement, preventing compromise of either property.
3Use of energy by moving object
If aluminium diffusion is increased to improve adhesion, then surface roughness increases, but porosity increases leading to premature oxidation
Solution Approach 1:
The invention precisely controls the aluminium concentration parameter through staged diffusion processes. The first stage creates a diffusion layer with controlled aluminium content for oxidation resistance. The second stage adds aluminium selectively to the surface region, creating roughness for adhesion without excessive bulk porosity. This parameter control prevents premature oxidation while achieving adhesion.
Solution Approach 2:
The invention creates local quality differentiation between the bulk and surface of the intermediate diffusion layer. The bulk maintains low porosity for oxidation resistance, while the surface develops controlled roughness for adhesion. This local differentiation resolves the contradiction between adhesion enhancement and porosity control.
4Ease of manufacture
If top coat is deposited on smooth surface, then deposition is easier, but adhesion and thermal fatigue resistance are reduced
Solution Approach 1:
The invention performs preliminary surface treatment of the intermediate diffusion layer to create controlled roughness before top coat deposition. This preliminary action of surface enrichment with aluminium creates a morphologically active surface that enhances adhesion and thermal fatigue resistance, while still allowing subsequent top coat deposition to proceed effectively.
Solution Approach 2:
The invention changes the surface morphology parameter of the intermediate diffusion layer by controlling aluminium diffusion and surface enrichment. This parameter transformation creates optimal surface roughness that balances ease of deposition with enhanced adhesion and thermal fatigue resistance.
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 method improves the adhesion and stability of the thermal barrier coating, enhancing its resistance to thermal fatigue and maintaining mechanical properties, while simplifying the production process and reducing costs, and can be applied to repair existing coatings.
Implementation Method 1
thermal treatment in a vacuum to enhance the surface roughness and adhesion between the bond coat and top coat, creating a stable and corrugated intermediate diffusion layer
Implementation Method 2
thermal treatment in a vacuum to enhance the surface roughness and adhesion
Implementation Method 3
Said intermediate diffusion layer DL has the property of being able to develop, when exposed to high temperatures (for example above 900°C), a protective surface film, which substantially consists of Al 2 O 3
Data Source
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AI summary
The invention refers to a process for the formation of a thermal barrier coating (102) on a substrate (101), comprising the steps of: a) applying a bond coat (103) on the substrate (101); b) subjecting the bond coat (103) to a low activity aluminizing process, thus obtaining, above the bond coat (103), a temporary intermediate diffusion layer; c) applying, on the temporary intermediate diffusion layer, aluminium powder in suspension with a solvent or aqueous base, said aluminium powder having size distribution from 15 to 150 µm; d) performing a thermal treatment in a vacuum at a pressure from 10-3 to 10-5 bars, at a temperature from 800°C to 1050°C and with an active phase having duration in the range of 60 minutes to 4 hours, thus obtaining above the bond coat (103) an enriched intermediate diffusion layer (105); and e) applying a definitive barrier layer (104) on said enriched intermediate diffusion layer (105).