Thermoplastic polymers such as polyamide 12 (PA12) are of great interest for functional coatings in industry due to their good material properties (e.g., chemical and wear resistance and biocompatibility). In order to provide a high local selectivity of polymer deposition and to shorten the process chain, a laser-based coating process represents a promising approach for generating functional coatings. In this work, a laser-based coating process for PA12 powder on stainless steel substrates is investigated experimentally by using a thulium-doped fiber laser with a wavelength of 1.94 μm. Due to the higher inherent absorption of the laser radiation in the powder material, a thulium-doped fiber laser is more appropriate for processing PA12 powder in comparison to more common near-infrared laser beam sources with wavelengths around 1 μm. The influence of the main process parameters (laser power, scanning speed, hatch distance, and substrate temperature) on the resulting coatings was evaluated. For this purpose, optical microscopic analyses were performed to characterize the coating surfaces and cross sections in terms of possible defects. In order to assess the adhesion between the coating and the substrate, cross-cutting values were determined. On the basis of the quality characteristics regarding the coating surface, a process window was determined to produce a closed melting film, which fully covers the metallic substrate. By an adjustment of the scanning speed (5 mm/s) and line overlap (50%/62.5%), a broadening of the process window could be achieved. An additional substrate heating (T ≥ 90°C) is an appropriate strategy, which enlarges the size of the process window significantly. Optical microscopy analyses and cross-cutting tests verified the suitability of a thulium-doped fiber laser for processing dense PA12 coatings with an adequate adhesion to the stainless steel substrate. The substrate temperature is a decisive process parameter to obtain a homogeneous morphology and to further improve the adhesion between the metallic substrate and PA12 layer.
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November 2021
Research Article|
October 20 2021
Consolidation of thermoplastic coatings by means of a thulium-doped fiber laser
Alexander Wittmann;
Alexander Wittmann
1
Institute of Photonic Technologies (LPT), Friedrich-Alexander-Universität Erlangen-Nürnberg
, Konrad-Zuse-Straße 3/5, Erlangen 91052, Germany
2
Erlangen Graduate School in Advanced Optical Technologies (SAOT)
, Paul-Gordan-Straße 6, Erlangen 91052, Germany
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Johannes Heberle;
Johannes Heberle
2
Erlangen Graduate School in Advanced Optical Technologies (SAOT)
, Paul-Gordan-Straße 6, Erlangen 91052, Germany
3
Bayerisches Laserzentrum GmbH (blz)
, Konrad-Zuse-Straße 2/6, Erlangen 91052, Germany
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Florian Huber;
Florian Huber
1
Institute of Photonic Technologies (LPT), Friedrich-Alexander-Universität Erlangen-Nürnberg
, Konrad-Zuse-Straße 3/5, Erlangen 91052, Germany
2
Erlangen Graduate School in Advanced Optical Technologies (SAOT)
, Paul-Gordan-Straße 6, Erlangen 91052, Germany
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Michael Schmidt
Michael Schmidt
1
Institute of Photonic Technologies (LPT), Friedrich-Alexander-Universität Erlangen-Nürnberg
, Konrad-Zuse-Straße 3/5, Erlangen 91052, Germany
2
Erlangen Graduate School in Advanced Optical Technologies (SAOT)
, Paul-Gordan-Straße 6, Erlangen 91052, Germany
3
Bayerisches Laserzentrum GmbH (blz)
, Konrad-Zuse-Straße 2/6, Erlangen 91052, Germany
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Note: Paper published as part of the special topic on Proceedings of the International Congress of Applications of Lasers & Electro-Optics 2021.
J. Laser Appl. 33, 042032 (2021)
Article history
Received:
July 02 2021
Accepted:
September 26 2021
Citation
Alexander Wittmann, Johannes Heberle, Florian Huber, Michael Schmidt; Consolidation of thermoplastic coatings by means of a thulium-doped fiber laser. J. Laser Appl. 1 November 2021; 33 (4): 042032. https://doi.org/10.2351/7.0000501
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