Improving surface properties by laser-based drying, gelation, and densification of printed sol–gel coatings
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In this article, an innovative laser-based inline-capable coating process for the production of highly wear resistant coatings is presented. A zirconia-based sol–gel material is applied onto hardened and tempered steel substrates by a PipeJet-based printing process and spin-coating. Green films with a thickness of 100–200 nm are produced. Drying, gelation, and transformation of the green films into mechanically resistant wear protection coatings is done by laser treatments. Due to the precise temporal and spatial controllability of the diode laser radiation it is possible to generate temperatures >1000°C, required for the crystallization of the films, as well as to minimize the thermal load of the substrate. The formation of a tetragonal ZrO2 phase within the films is achieved by the laser treatment. According to finite-element calculations the temperature penetration depth of temperatures >150°C (thermal stability of the substrate around 180°C) is reduced to 20–100 μm by using pulsed diode laser radiation. The evolution of the layer thickness as well as chemical and morphological coating properties is investigated by white light interferometry, Fourier transform infrared spectroscopy, and grazing-incidence XRD measurements.
KeywordsLaser materials processing Thin film Sol–gel Zirconia Printing Wear protection
The presented research is built on a project funded by the German Federal Ministry of Education and Research within the framework of the funding measure “Material Processing with Brilliant Laser Sources” (MABRILAS). The authors would also like to thank the Schaeffler Technologies AG & Co. KG, Merck KGaA Darmstadt, DILAS GmbH and Biofluidix GmbH for the excellent cooperation within the project consortium FunLas.
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