Successfully completed doctorate
On 19 December 2023, Daniel Metzner, M.Sc., received his doctorate in engineering from the Faculty of Mechanical Engineering at Chemnitz University of Technology. The examinations included the viva voce and a specialist presentation with defence. His dissertation is entitled „Laser microstructuring of high-alloy steel – Basic investigations into the use of high-frequency pulse sequences of ultra-short laser pulses“.
Dr Metzner wrote his thesis while working as a research assistant at the Laser Institute at Mittweida University of Applied Sciences. The dissertation was written in a co-operative process between Mittweida University of Applied Sciences and Chemnitz University of Technology. It was supervised by Professors Steffen Weißmantel and Thomas Lampke.
This thesis deals with the use of high-frequency pulse sequences of ultrashort laser pulses for laser micromachining of high-alloy steels. The influence of different laser parameters on the ablation efficiency, the generated surface structures and on physical processes during laser micromachining is analysed. For this purpose, X90CrV18 steel was irradiated with ultrashort laser pulses and extremely high pulse repetition frequencies within a pulse sequence of up to 2.5 GHz. The ablation volumes and structure diameters per laser pulse, the emitted secondary radiation within a pulse sequence and the resulting topography after irradiation were empirically analysed. Simulations of the interaction of individual ultrashort laser pulses and pulse sequences of ultrashort laser pulses with high-alloy steel were carried out in order to gain a fundamental understanding of the physical mechanisms at work during irradiation in the interaction zone. Findings on functional relationships between the laser parameters of ultrashort laser pulses and the resulting ablation depth and melt film formation were derived from the results of extensive simulations. In addition, the results of the volume ablated per laser pulse allow conclusions to be drawn about shielding processes within a pulse sequence by an existing ablation cloud or by a plasma. An iterative shielding of the laser radiation of subsequent laser pulses due to the interaction with an existing ablation cloud occurs primarily when using pulse sequences with pulse repetition frequencies in the MHz range. Based on the ablation volume per laser pulse at pulse repetition frequencies in the GHz range, the laser radiation of subsequent laser pulses of a pulse sequence is almost completely shielded by the plasma. Based on the new findings of this work, optimum process parameters for the generation of 3D microstructures were determined in order to achieve the highest possible efficiency and productivity with low surface roughness at the same time
The entire WOT team congratulates you on your promotion!
Photo: The photo shows the people involved in the process (from left): Prof Michael Groß, Dr Daniel Metzner, Prof Steffen Weißmantel, Prof Thomas Lampke. (Photo: private)
8.1.2024 – Personnel of the professorship ( thomas.lampke@mb… )
