PhotonicsViewsVolume 18, Issue S1 p. 18-19 Surface ModificationFree Access Laser Chemical Machining with High Process Pressure Increase of the removal rate in laser chemical machining by increasing the process pressure Marcel Simons, Corresponding Author simons@bias.de www.bias.de +49 421 218-58036 BIAS – Bremer Institut für angewandte Strahltechnik, Klagenfurter Str. 5, 28259 BremenSearch for more papers by this authorTim Radel, BIAS – Bremer Institut für angewandte Strahltechnik, Klagenfurter Str. 5, 28259 BremenSearch for more papers by this author Marcel Simons, Corresponding Author simons@bias.de www.bias.de +49 421 218-58036 BIAS – Bremer Institut für angewandte Strahltechnik, Klagenfurter Str. 5, 28259 BremenSearch for more papers by this authorTim Radel, BIAS – Bremer Institut für angewandte Strahltechnik, Klagenfurter Str. 5, 28259 BremenSearch for more papers by this author First published: 17 February 2021 https://doi.org/10.1002/phvs.202100003AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, IssueS1February 2021Pages 18-19 ReferencesRelatedInformation

The laser chemical process is a material-removing machining process in the micro range. The process is based on a laser-assisted etching process between an electrolyte and a metallic workpiece. Local overheating causes a laser-induced electrolyte boiling process, which limits the laser chemical process window. In order to reduce the laser-induced electrolyte boiling process and thus expand the process window, the laser chemical process is carried out at different electrolyte start temperatures and thus different electrolyte viscosities and surface tensions. The experimental investigations were carried out on Titanium Grade 1 with the electrolytes phosphoric acid and sulfuric acid at different electrolyte temperatures and laser powers to determine the limits of the process window by evaluating the properties of the removal cavities. As a result, the process window is extended at lower electrolyte viscosities. Thereby, the electrolyte viscosities have no influence on the geometric shape of the removal. The extension of the process window is attributed to the fact that a reduction in electrolyte viscosity results in a less pronounced formation of the boiling process, the bubble diameters decrease, and the shielding effect of the bubbles is reduced.

Laser chemical machining (LCM), a non-conventional removal process, is based on the thermal activation of heterogeneous chemical reactions between an electrolyte and a metallic surface. When machining metallic surfaces with LCM, large fluctuations in removal quality can occur due to rising boiling bubbles. To delay electrolyte boiling the approach was to increase the process pressure.

Die Ultrakurzpuls (UKP)-laserbasierte Bearbeitung erlaubt die Herstellung von Netzstrukturen mit verschiedenen Transmissionsgraden. Vorteile der UKP-laserbasierten Herstellung der Netze liegen vor allem in der hohen Präzision und Bearbeitungsgeschwindigkeit. Die UKP-Laserbearbeitung ermöglicht die Herstellung von Netzen aus Aluminium in hoher Qualität, bezogen auf die Stegbreitenabweichung von < 8 µm, mit variablen Transmissionsgraden. Ultra-short pulse (USP) laser based processing enables the production of mesh structures with different degrees of transmission. The advantages of USP-based production of mesh structures are mainly the high precision and processing speed. USP laser processing enables the production of meshes of aluminum in high quality, with respect to the mesh width deviation of < 8 µm with variable transmission degrees.

Laser Chemical Machining (LCM) is a non-conventional removal process, based on a precise thermal activation of heterogeneous chemical reactions between an electrolyte and a metallic surface. Due to local overheating during the process, boiling bubbles occur, which can impair the removal quality. In order to reduce the amount of bubbles, the laser chemical process is performed at different process pressures. Removal experiments were performed on Titanium Grade 1 using the electrolyte phosphoric acid at various process pressures, machining speeds and laser powers in order to determine the limit of the process window by evaluating the characteristics of the removal cavities. As a result, the process window for non-disturbed laser chemical machining is widened at higher process pressures. The process pressures have no influence on the geometric shape of the removal. The expansion of the process window is attributed to the fact that at higher process pressures the saturation temperature of the electrolyte rises, so that bubble boiling starts at a higher surface temperature on the workpiece induced by the laser power. The removal rate could be increased by a factor of 2.48 by increasing the process pressures from ambient pressure to 6 bar, thus taking an important step towards the economic efficiency of the laser chemical machining.

Laser Chemical Machining (LCM) is a non-conventional processing method, which enables very accurate and precise ablation of metallic surfaces. Material ablation results from laser-induced thermal activation of heterogeneous chemical reactions between electrolytes and a metallic surface. However, when processing metallic surfaces with LCM, large fluctuations in ablation quality can occur due to rising bubbles. The for-mation of bubbles during laser chemical machining and their influence on the ablation quality has not been investigated. For a more detailed investigation of the bubbles, ablation experiments on Titanium and Ce-ramic under different thermal process conditions were performed. The experiments were recorded by a high-speed camera. The evaluation of the video sequences was performed using Matlab. The resulting bubbles were analyzed regarding their size and frequency. The results show that boil-ing bubbles formed on both materials during processing. Titanium also produces smaller bubbles, which can be identified as process bubbles ac-cording to their size. Furthermore, it was found that undisturbed laser chemical ablation can be achieved in the presence of a boiling process, since both boiling bubbles and process bubbles were detected during machining within the process window.