Laser-Structured Substrate Surfaces for Thermal Spray Adhesion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The adhesive strength of thermally sprayed layers on substrates, particularly fiber composite materials, is limited due to smooth surfaces, leading to inadequate clamping and increased stress peaks, which are difficult to address with existing methods that require additional adhesion promoters or generate homogeneous roughness.
Innovation Solution
A method using intense pulsed laser radiation to create multiscale surface structures on a sub-micrometer and micrometer scale, adjusting process parameters like power density, pulse length, and spatial overlap to generate irregular roughness, optimizing adhesion and crack propagation resistance by producing specific pot-like and cauliflower-like structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the substrate surface is left smooth (as in fiber composite materials), then the production process is simple and costs are low, but the adhesive strength of thermally sprayed layers is insufficient and clamping is inadequate
Solution Approach 1:
The surface structure is segmented into multiple scales: macroscopic roughness features (hundreds of micrometers) that provide clamping points, and microscopic features (micrometers) that increase surface area and mechanical interlocking. This multi-scale segmentation allows the surface to provide adequate adhesion without requiring additional adhesion promoter layers.
Solution Approach 2:
The laser treatment creates locally optimized surface structures with specific roughness characteristics in different areas. The process allows for spatially varying roughness patterns that are tailored to local adhesion requirements, with deeper structures in areas needing stronger mechanical interlocking and finer structures in areas requiring stress distribution.
2Strength
If adhesion promoter layers with increased irregular roughness are applied using suspension application and sintering technology, then adhesive strength is improved, but production costs increase and the roughness is mesoscopically homogeneous
Solution Approach 1:
The mechanical suspension application and sintering process is replaced by a laser-based ablation process. The laser directly removes material from the substrate surface to create the desired roughness profile, eliminating the need for additional adhesion promoter materials and the complex suspension application and sintering equipment required.
Solution Approach 2:
The laser processing parameters (pulse duration, power density, scanning speed, pulse overlap) are optimized to directly generate the required surface roughness characteristics. By adjusting these parameters, the process produces the desired mesoscopic and microscopic surface features in a single step, reducing production costs compared to multi-step adhesion promoter application.
3Strength
If pulsed laser radiation is used to generate fractal geometries on a sub-micrometer scale, then adhesion is improved, but the process requires precise control of process parameters to achieve the desired multiscale structure
Solution Approach 1:
The laser operates in pulsed mode with periodic action, where each pulse creates a controlled ablation event. The pulse frequency, duration, and overlap are precisely controlled to generate the desired fractal geometries and multiscale surface structures. This periodic pulsed action allows for cumulative building of complex surface features while maintaining precise control over the final surface morphology.
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 enhances the adhesion and cyclability of thermally sprayed layers by creating tailored surface structures that account for the inhomogeneous properties of substrates, reducing production costs and avoiding the need for additional heat treatments, while effectively limiting crack propagation.
Implementation Method 1
A method using intense pulsed laser radiation to create multiscale surface structures on a sub-micrometer and micrometer scale
Implementation Method 2
The laser beam is then directed over the entire surface of the substrate by means of masks or other optical aids, with a simple regular sine function being imaged on the surface of the substrate by ablation
Implementation Method 3
adjusting process parameters like power density, pulse length, and spatial overlap to generate irregular roughness
Implementation Method 4
producing specific pot-like and cauliflower-like structures
Data Source
Figure 1a~3b
Figure 4a~5b
Figure 5c~6b
AI summary
The invention relates to a method for generating a structured surface on a substrate, in which surface structures with dimensions in the sub-micrometre range are generated by means of treatment with an intensive pulsed laser beam, wherein by varying the method parameters of focus diameter, peak pulse power, pulse energy, point spacing, pulse length, pulse spacing and/or pulse sequence, a multiscale surface structure in the sub-micrometre and micrometre range is generated by means of, in part, material-removing treatment. The method makes it possible to adapt the microstructure to be generated to the substrate surface properties, which are intrinsically inhomogeneous in the sub-millimetre range, and to vary the method parameters accordingly. In an advantageous embodiment, the method parameters to be set locally are selected at a point in time very close to machining by means of a parallel evaluation of sensor data of the substrate surface.