Multilayer Thermal Spray Coating Without Surface Preparation
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Solution Overview
Problem
Conventional thermal spraying methods face challenges in achieving excellent adhesion of coatings to substrates without surface preparation, particularly for mechanically fragile or complex-shaped parts, due to issues like wettability, adhesion, and differential expansion, and require costly or stress-inducing surface activation techniques.
Innovation Solution
A method involving a multilayer coating process where a nanostructured or finely structured layer is deposited by liquid thermal spraying followed by a microstructured layer using conventional thermal spraying, without prior surface preparation, to achieve strong adhesion and thick coatings exceeding 100 μm thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal spraying methods are used to deposit coatings on substrates, then coating deposition can be achieved, but adhesion quality deteriorates without surface preparation
Solution Approach 1:
The patent applies preliminary action by depositing a nanostructured layer first as a preparatory step before depositing the functional microstructured layer. This preliminary nanostructured layer creates an optimized surface structure that enhances adhesion without requiring mechanical surface preparation of the substrate. The nanostructured layer acts as an intermediate layer that prepares the surface for subsequent coating deposition.
Solution Approach 2:
The patent utilizes parameter changes by transitioning from microstructured particles to nanostructured particles in the coating composition. This change in particle size parameter enables the formation of a finely structured layer with superior adhesion properties. The nanostructured particles (1-100 nm) create a different microstructure compared to conventional micrometric particles, allowing for enhanced bonding at the substrate-coating interface.
2Reliability
If surface preparation techniques are used to improve adhesion, then adhesion quality improves, but production cost and process complexity increase
Solution Approach 1:
The patent extracts the surface preparation function from external mechanical processes and incorporates it into the coating deposition process itself. By using nanostructured particles, the coating material itself performs the surface preparation function through its unique microstructure, eliminating the need for separate mechanical surface preparation equipment and processes.
Solution Approach 2:
The nanostructured layer acts as an intermediary between the substrate and the functional coating layer. This intermediate layer provides the adhesion enhancement function that would otherwise require complex surface preparation of the substrate. The nanostructured layer mediates the interface between different materials, creating a transition zone that improves bonding.
3Reliability
If liquid thermal spraying is used to deposit nanostructured layers, then adhesion improves, but coating thickness is limited
Solution Approach 1:
The patent segments the coating into two distinct functional layers: a nanostructured layer (1-100 nm particles) providing adhesion, and a microstructured layer (micrometric particles) providing the required thickness and functional properties. This segmentation allows each layer to be optimized for its specific function, with the nanostructured layer ensuring adhesion and the microstructured layer providing the necessary coating thickness without the limitations of single-phase liquid spraying.
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 enables the preparation of thick, adherent coatings with excellent adhesion to substrates without surface preparation, overcoming the limitations of conventional dry processes and liquid-based methods, allowing for coatings on complex shapes and reducing production costs.
Implementation Method 1
The projection gas, brought to a high temperature, is thus an enthalpy and kinetic source which makes it possible to heat the particles up to their melting point or beyond, and to impart a certain speed to them.
Implementation Method 2
These particles are injected into the projection gas using a vector gas, called carrier gas. The user must match the momentum of the carrier gas and the particles with that of the blasting gas to allow the particles to penetrate well into the blasting gas.
Implementation Method 3
The accumulation of the particles on the substrate makes it possible to carry out the coating by stacking these particles.
Data Source
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Figure 3~4
AI summary
The invention relates to a method for creating a multilayer coating on a substrate surface by means of at least one thermal spraying method, wherein according to said method the following consecutive steps are carried out: a) a nanostructured or finely structured first layer of a first material is deposited by means of a liquid thermal spraying method, the substrate surface not undergoing any preparation or activation treatment other than an optional cleaning treatment prior to depositing the nanostructured or finely structured first layer; and b) a microstructured second layer of a second material is deposited onto the nanostructured or finely structured first layer by means of a thermal spraying method. The first layer from step a) is a coupling layer for optimizing the adhesion of the layer from step b) without surface preparation or activation.