Conference Agenda

Program for LiM 2021
Location: Room 4
ICM 1st Floor 433
 
Date: Tuesday, 22/June/2021
10:00am - 11:00amMacro: Cutting 1
Location: Room 4
Session Chair: Jannik Lind, University of Stuttgart, Germany
Room 4 
 
10:00am - 10:30am

Invited Talk: Laser cutting - past and present

John Powell

Laser Expertise, United Kingdom

Laser Cutting is over 50 years old! It has passed though its childhood, difficult teenage years, and early adulthood, to become the mature technology we know today.

Dr John Powell has worked in the subject since the early 1980’s and will present a talk which describes some of the early difficulties of the process and how they were overcome.

The talk will combine a general history of laser cutting with personal anecdotes - including a few comments on laser cutting in the days before laser safety was invented (Luckily, the plastic pipes exploded before the flames reached the hydrogen bottle).



10:30am - 10:45am

Fundamental characteristics of fiber laser beam sawing of 10 mm thick stainless steel

Madlen Borkmann, Achim Mahrle, Patrick Herwig, Andreas Wetzig

Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS Dresden, Germany

AISI 304 stainless steel plates of 10 mm thickness were separated by fibre laser beam sawing trials. The applied sawing technique as a new variant of laser cutting with an oscillating beam relies on periodical changes of the focusing length of the optical setup by integrated mirrors with adjustable curvature radius. As a result, the focal plane position can be forced to oscillate with a frequency of up to 4800 Hz and amplitudes up to 6 mm. The resulting temporally averaged beam profile is characterized by a nearly constant beam diameter over the whole spatial oscillation range. Variations of oscillation frequency, amplitude and nominal focal layer position were performed to get first insights into the effect mechanisms of fibre laser beam sawing. It is found that the cut kerf geometry can be adjusted to improve cutting gas flow characteristics and melt removal.



10:45am - 11:00am

Monitoring of the melt pool for fiber laser cutting using a high-speed camera

Max Schleier1, Benedikt Adelmann1, Uwe Glatzel2, Ralf Hellmann1

1University of Applied Sciences Aschaffenburg; 2University Bayreuth

We demonstrate an in-situ and coaxial monitoring system based on a high-speed camera with a spectral response in the visible range, which is designed to be integrated into a cutting head between the collimator and processing lens. The thermal radiation from the melt pool is measured in the visible spectral range, without external illumination, spatially and temporally resolved from the top view. The dependencies of the laser power and feed rate on the spectral and geometric information captured from the images of the melt pool in the cut kerf are evaluated. In addition, we developed and show an algorithm to detect incomplete cuts caused by laser power and feed rate from the captured images.

 
11:15am - 12:30pmMacro: Cutting 2
Location: Room 4
Session Chair: Jannik Lind, University of Stuttgart, Germany
Room 4 
 
11:15am - 11:30am

3D simulation of spatial and temporal modulation in laser beam fusion cutting

Ulrich Halm1, Wolfgang Schulz1,2

1RWTH Aachen University, Germany; 2Fraunhofer Institute for Laser Technology ILT

Mean profile height and perpendicularity are, along with adherence of dross, the main quality features in laser fusion cutting of sheet metals. Research indicates that the dynamics of the thin melt film and the beam shape have a strong effect on these quality features. Recent measures to reduce the mean profile height include spatial and temporal modulation of the laser beam. A 3D simulation of the melt film dynamics is used to analyze the effect of these measures on the mean profile height and the perpendicularity of the cut surface. Insight into the temperature distribution inside the solid material allows a deeper understanding of how spatial and temporal modulation of the laser beam act on the cut surface. Furthermore, the effect of artificial additional beam sources can be analyzed. The most positive effect on the cut surface was created by a homogenous illumination of the side of the cutting front.



11:30am - 11:45am

Potential health risks due to emission of hazardous substances during outdoor laser cutting

Jürgen Walter, Christian Hennigs, Michael Hustedt, Jörg Hermsdorf, Stefan Kaierle

Laser Zentrum Hannover e.V., Germany

In contrast to well-defined industrial laser processes, there is limited knowledge regarding secondary hazards due to emission of gaseous and particulate hazardous substances during outdoor-laser applications, such as facades cleaning, pipelines repair and rescue from crashed vehicles, including hazardous-substances capturing and handling.

According to the German Clean-Air Act (TA-Luft), results of emission measurements in the exhaust air of a 2.5 kW laser-cutting process of typical automotive-multilayer structures were correlated with assessment criteria for the main hazardous components found, leading to requirements for exhaust-air cleaning. Complementary, air measurements at the operation site according to TRGS 402 were performed to evaluate whether the inhalation-exposure limits for hazardous substances released from the laser-process zone and not captured by the exhaust equipment were complied with, considering assessment criteria according to TRGS 900 and TRGS 910. The investigations showed that additional measures to reduce hazardous-substance concentrations are dispensable, if the exhaust unit is dimensioned correctly.



11:45am - 12:00pm

Striation formation at the cut edge of oxygen assisted fibre laser cutting

Handika Sandra Dewi

Luleå University of Technology, Sweden

Laser cut edges show parallel grooves features or striations. A high-quality cut edge is identified by fine striations at the cut edge. In order to gain a better understanding in striation formation at the cut edge and improve the cutting quality, striations at the cut edge and melt flow during laser cutting processes were investigated. Oxygen assisted fibre laser cutting processes were carried out on 1-mm-thick and 20-mm-thick steels at varied processing parameters and recorded using high speed imaging with borosilicate glass as replacement edge. The size of striations at the cut edge and frequency of the molten ripples were measured. The striation widths show a linear correlation with the gas pressure and cutting speed, but inverse correlation was found between striation widths and the nozzle diameter. Gas pressure is most likely the main influencing factor affecting the striation widths.



12:00pm - 12:15pm

Advanced beam shaping for high power cutting & welding

Natalia Trela-McDonald, Alex Griffiths, Gilles Diederich, Eoin Murphy

PowerPhotonic Ltd, United Kingdom

Beam shaping of light from high power fiber lasers to improve cutting or welding performance can be challenging, due to (i) high power density; (ii) short length optical train; (iii) uniformity of the shaped beam over the tolerance range of the application. We present novel approaches to the design and manufacture of high efficiency beam shaping elements for multi-mode and single-mode fiber lasers. Beam structures that are emerging as important for industrial processing – such as rings – are considered. Importantly, these designs can be manufactured with sufficient low loss and low scatter by a laser-writing freeform optical manufacturing technique.

 
1:30pm - 2:30pmMacro: System Technology and Process Control 1
Location: Room 4
Session Chair: Manuel Henn, Institut für Strahlwerkzeuge IFSW, Germany
Room 4 
 
1:30pm - 1:45pm

Open-loop control of complex pulse shapes for laser beam welding

Marc Seibold, Klaus Schricker, Jean Pierre Bergmann

Technische Universität Ilmenau, Germany

Pulsed laser beam welding is of high importance in micro-welding applications and used for materials susceptible to hot cracking, e.g. 6xxx aluminum alloys. Pulse shapes are adjusted to prevent hot cracks by reducing solidification rates which is accompanied by decreased welding speeds. Numerical simulations are now used for optimizing the tradeoff between crack-free welds and highest possible welding speeds. This procedure requires small deviations between the nominal value of the laser beam power calculated by numerical simulations and the actual value in the experiment. A methodology is developed and validated for fiber laser and Nd:YAG laser beam sources (IPG YLM-450/4500-QCW, LASAG SLS 200CL60HP) using different pulse shapes. The differences between nominal and actual values were identified by high-speed power measurements and reduced from 13% down to 2% for complex pulse shapes over time. This paper will show how to set up power compensation to emit an accurate complex pulse shape.



1:45pm - 2:00pm

Monitoring of laser welding and cladding processes with edge artificial intelligence combining thermal and visual cameras

Beñat Arejita1,2, Juan Fernando Isaza1, Aitzol Zuloaga2

1EXOM Engineering, Spain; 2UPV/EHU, Spain

Laser welding and cladding are well known for their complexity and high dynamics, therefore being challenging for in situ and real-time quality control and monitoring. To tackle this challenge, this work presents a dedicated hardware implementation performing real time image processing of a multi camera configuration with a visual and a NIR camera coaxially set up with the laser beam and an off-axis stereoscopic camera. The coaxial images are analysed by edge artificial intelligence technics allowing real-time closed loop temperature control and an adaptive scanner head positioning to perform a precise melt pool monitoring and process traceability. In parallel, the volumetric positioning of the scanner head and laser job interpretation are done using the stereoscopic information, linking it with the job definition of the part being processed. The presented system can be used during Nickel-strip welding of big battery packs or during identification of milled recesses in cladding applications.



2:00pm - 2:15pm

Real-time adaptation of the dross attachment level in the laser cutting process based on process emission images

Matteo Pacher1, Mara Tanelli2,4, Silvia C. Strada2, Davide Gandolfi1, Sergio M. Savaresi2, Barbara Previtali3

1Adige S.P.A., BLMGROUP, Via per Barco 11, 38056, Levico Terme (TN), Italy; 2Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, via G. Ponzio 34/5, 20133 Milano, Italy; 3Dipartimento di Meccanica, Politecnico di Milano, Via La Masa 1, 20156 Milano, Italy; 4Istituto di Elettronica e Ingegneria dell’Informazione e delle Telecomunicazioni - IEIIT CNR Corso Duca degli Abruzzi 24, 10129 Torino, Italy

In the field of melt and blow metal laser cutting, dross attachment is the most important quality indicator. Accordingly, process parameters are generally optimized to ensure high productivity while minimizing the level of dross attachment. The resulting set of parameters often penalizes the productivity to increase reliability. As a result, there exists a productivity margin that could be exploited by controlling the quality level in closed-loop, thus optimizing the process parameters in real-time. To closed-loop control the process, two steps must be performed: a real-time, reliable estimate of cutting quality must be available and, a closed-loop controller should adapt the process parameters according to the desired quality level. This work presents the design and experimental validation of a real-time estimation and control algorithm based on process emission images that adapts the cutting speed to fulfill a desired dross attachment level.

Project Name: LT4.0. Funding from LP6/99 Autonomous Province of Trento

 
2:45pm - 4:00pmMacro: System Technology and Process Control 2
Location: Room 4
Session Chair: Jonas Wagner, Universität Stuttgart, Germany
Room 4 
 
2:45pm - 3:00pm

Active mirrors for plan field correction in laser material processing

Paul Böttner1, Aoife Brady1, Claudia Reinlein3,2, Ramona Eberhardt1, Stefan Nolte1,2

1Fraunhofer IOF, Germany; 2FSU Jena, Germany; 3Robust AO GmbH, Germany

This paper reports on an approach to increase the scan field and the dynamic range of post objective scanners. An active mirror in combination with a fixed focusing lens is used to adjust the optimal focus length depending on the beam position in the scan field.

The active mirror has an adjustment range from infinity to 0.5 dpt with a step response time of 2 ms. The scan field is determined by the focal length of the focusing lens. When using a focal length of 250 mm, a scan field of (100 x 100) mm² is achieved. Doubling the focal length increases the scan field to (500 x 500) mm². Measurements with a raw beam diameter of 20 mm and a wavelength of 1064 nm provide a spot diameter of 34 µm with a focal length of 250 mm and 75 µm with a focal length of 500 mm.



3:00pm - 3:15pm

Fixture-free laser-beam-welding

Georgij Safronov1, Alexander Grimm1, Florian Schlather1, Markus Puschmann2, Philipp Ronald Engelhardt1, Markus Lachenmaier1

1BMW AG, Germany; 2Fraunhofer Institute for Machine Tools and Forming Technology, Germany

Today’s automotive Bodyshop is dominated by resistance-point-welding due to low cost and robustness, especially regarding part-quality-variations. In contrast laser-beam-welding is struggling to create a solid business case in big numbers even so it has technological advancements like the welding-speed. To economically resolve this competition, we need an approach to create a balanced synergy between both joining methods. BMW together with the Fraunhofer Society (IWU) and the Technical University Munich (iwb) approached this challenge by developing a method to combine both welding procedures through a lap-joint-flange integrated geometry, which can be brought in off-tool in the press-shop.

These functional geometries allow us to use the advantages of resistance-point-welding to fix the geometry and create a laser-suitable gap-situation without clamping-tools for the following laser-welding. We also proved the technological and the financial viability of this method and we believe this could be a game-changer for laser-welding in the automotive industry.



3:15pm - 3:30pm

Remote laser welding system with automatic 3D teaching, in-line 3D seam tracking, and adaptive power control

Matija Jezersek1, Matjaž Kos1, Erih Arko2, Hubert Kosler2

1University of Ljubljana, Faculty of Mechanical Engineering, Laboratory for Laser Techniques, Aškerčeva cesta 6, 1000 Ljubljana, Slovenia; 2Yaskawa Slovenija d.o.o., Lepovče 23, 1310, Ribnica, Slovenia

An adaptive remote laser welding system, based on triangulation feedback control is presented. It enables off-line measuring of a workpiece 3D shape, in-line 3D seam tracking, and in-line laser power control, which are extremely important features for producing sound welds on complex geometries. The 3D measuring is done by a triangulation camera and the laser’s pilot beam. The same camera is utilized to determine the 3D seam position and to monitor the key process features, including the weld penetration depth.

Results show high 3D measuring precision in the lateral (0.05 mm) and vertical (0.3 mm) direction. Additionally, laser power control significantly reduces penetration depth and plasma oscillations. Thus, adaptive laser welding can be used for small series and customized production of parts where a highly flexible, precise, and cost-effective joining technology is required.



3:30pm - 3:45pm

Image-based Real-Time Defect Detection during Laser Welding using Ensemble Deep Learning on Low Power Embedded Computing Boards

Christian Knaak, Jakob von Eßen, Peter Abels, Arnold Gillner

Fraunhofer ILT, Germany

Advanced and intelligent process monitoring strategies are required to enable an unambiguous diagnosis of the process situation and thus of the final component quality. Additionally, the ability to recognize the current process situation in terms of quality is also a key requirement for autonomous manufacturing systems. To address these needs, this study investigates a novel ensemble deep learning architecture based on convolutional neural networks (CNN), gated re-current units (GRU) combined with high performance classification algorithms such as k-nearest neighbors (kNN) and support vector machines (SVM). The architecture uses spatio-temporal features extracted from infrared image sequences to locate critical welding defects including lack of fusion (false friends), sagging and lack of penetration, and geometric deviations of the weld seam. In order to evaluate the proposed architecture, this study investigates a comprehensive scheme based on classical machine learning methods using manual feature extraction and state of the art deep learning algorithms. Optimal hyperparameters for each algorithm are determined by an extensive grid search.



3:45pm - 4:00pm

System design for reliable and robust laser-welding of copper in automotive series production

Stefan Mücke, Pravin Sievi, Steffen Walter, Florian Albert

Scansonic MI GmbH, Germany

The evolution of mobility away from ICEs towards electric or electrified drives also created some new challenges for the series production of drive train components. With copper, a new material moves into focus in the drive train which needs to be welded. No matter if e-motors, e-boxes or batteries, copper needs to be welded and the laser fits best for the requests in most cases. The presentation will focus on what has to be considered for welding copper and to face these issues with an intelligent system-design to fit series production needs. Beside the design of the welding system with high-speed scanners and arrangement of the necessary components, the presentation also will focus on the matter of detecting the welding areas correctly to create a robust process that reduces costs and can cope with series production conditions.

 

 
Date: Wednesday, 23/June/2021
10:00am - 11:00amMicro: Surface Functionalization 1
Location: Room 4
Session Chair: Dr. Thomas Stichel, Bayerisches Laserzentrum GmbH (blz), Germany
Room 4 
 
10:00am - 10:15am

Fabrication of complex periodic patterns on a metallic drum for high throughput roll-to-roll processing

Bogdan Voisiat1, Max Menzel1, Wei Wang1, Yangxi Fu1, Marcos Soldera1, Andrés Fabian Lasagni1,2

1Dresden University of Technology, Germany; 2Fraunhofer Institute for Material and Beam Technology, Germany

In this study, the development of complex periodic structures on massive metal drums by means of direct laser interference patterning (DLIP) is demonstrated. The DLIP technology allows the formation of high-resolution periodical structures (even with sub-micrometer resolution) at high fabrication speeds on large surface areas. These advantages drastically reduce the patterning costs of the drums that are broadly used in roll-to-roll processing. We demonstrate the ability to control individually each laser spot (e.g. period) to form complex periodical patterns to be used as decorative elements exhibiting structural colors. These patterns are then replicated on a polymer foil by an industrial hot-embossing roll-to-roll process at speeds up to 50 m/min. This process brings the industrial fabrication of such patterns to the next level in terms of throughput and is thus suitable for mass production.



10:15am - 10:30am

Improving the bond strength of metal-FRP-hybrids with thermal sprayed copper using pulsed laser-based processing approaches

Jana Gebauer1, Volker Franke1, Kevin Gustke2, Udo Klotzbach1, Thomas Lampke2, Andrés Fabian Lasagni1,3

1Fraunhofer IWS, Germany; 2Chemnitz University of Technology, Germany; 3Technische Universität Dresden, Germany

Ablation processes during laser treatment of carbon fiber-reinforced plastics with pulsed lasers of various wavelengths and pulse durations are investigated. Three general surface pretreatment strategies are used, including laser-roughening, selective matrix removal and laser micro-structuring. Various ablation mechanisms, including evaporation and matrix delamination are observed, depending on the employed laser source. Selected laser structured substrates were coated with copper by a wire arc spraying process. Bonding strengths up to 18.1 ± 2.6 MPa and 18.7 ± 2.0 MPa were achieved in pull-off tests and shear tensile tests, respectively, by the combination of the roughening process and the micro-structuring approach. Consequently, the bonding strength could be increased up to ~ 200 % compared to the common pre-treatment by grit-blasting.



10:30am - 10:45am

Low temperature and high concentration laser doping system for fabrication of 4H-SiC power devices

Toshifumi Kikuchi1, Takuma Yasunami1, Akira Mizutani2, Daisuke Nakamura1, Hiroshi Ikenoue1

1Grad. Sch. ISEE. Kyushu Univ.,; 2Dept. of Gigaphoton Next GLP, Kyushu Univ.

We propose a high-concentration and low crystal damage doping method by irradiating KrF excimer laser to the deposited films contains of dopant atoms on the 4H-SiC surfaces. This laser doping method is a low-temperature process that reduces the thermal stress to the substrate, and can achieve doping concentration of ~1020 cm-3 or more, which exceeds the limit of the ion implantation method.

In this study, we investigated the peak energy dependence of the crystal damage and surface roughness by controlling the pulse width of the laser for doping. As a result, it is found that the crystal damage and surface roughness were reduced by suppressing the peak energy. In addition to this, we report on the construction of a laser doping system to improve compatibility with the manufacturing process of 4H-SiC power devices.



10:45am - 11:00am

Excimer laser annealing method with the controlled grain size of poly-Si films for large display panels

Akira Mizutani1, Fuminobu Hamano2, Daisuke Nakamura2, Tetsuya Goto3, Aid SitiRahmah4, Hiroshi Ikenoue1,2

1Department of Gigaphoton Next GLP, Kyushu University; 2Graduate School of Information Science and Electrical Engineering, Kyushu University; 3New Industry Creation Hatchery Center, Tohoku University; 4Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia

Low-temperature polycrystalline Si thin film transistors (TFTs) crystallized using the Excimer Laser Annealing (ELA) method have been used as backplanes for active matrix organic displays due to their high electron mobility. However, the current ELA method requires a long axis of the line beam which is equivalent to the short axis of the substrate's size, and there is a limitation in application to a large glass substrate. One of the methods to overcome this problem is to anneal the entire surface by folding back the beam. However, in the overlapping region of the laser, the crystal grain size becomes large, and the device characteristics become ununiform. In this study, we report on the results of evaluating the TFT characteristics by controlling the crystal grain position and size by laser annealing with a periodic intensity distribution induced by a dot array mask to form the same crystal grain size in the overlap regions.

 
11:15am - 12:30pmMicro: Surface Functionalization 2
Location: Room 4
Session Chair: Martin Hohmann, Institute of Photonic Technologies (LPT), Germany
Room 4 
 
11:15am - 11:30am

Molded parts with functional surfaces – how laser microstructuring can be used for low-cost mass products

Maik Steinbach, Jürgen Koch, Peter Jäschke, Stefan Kaierle, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

Microstructuring via ultrashort pulse laser enables the targeted generation of functional surface structures. With this technology, progress in material behavior has been shown in tribological, optical and haptical properties, liquid wettability and cell adhesion. In cases where the effect is mainly based on the laser-generated microstructures instead of laser-induced chemical changes of the surface material, injection molding offers a possibility to make the usually high-priced laser surface functionalization accessible to low-cost mass products. This technique leaves the chemistry of the molded parts unaffected, which makes it especially attractive for biomedical applications. Molding inverts the surface topography and can be associated with resolution, durability and demoldability restrictions. We present our current results and findings on basic as well as on application-oriented issues. Selected applications including a technique for piracy protection are discussed.



11:30am - 11:45am

Towards optimization of femtosecond laser pulse nano-structuring for high-intensity laser interactions

Ulrich Teubner1,3, Imgrunt Jürgen1, Andreev Alexander1,2

1Institut für Laser und Optik, Hochschule Emden/Leer – University of Applied Sciences, Constantiaplatz 4, 26723 Emden, Germany; 2Sankt Petersburg State University, Sankt Petersburg, Russia; 3Institut für Physik, Carl von Ossietzky Universität Oldenburg, Ammerländer Heerstr. 114-118, 26111 Oldenburg, Germany

The interaction of intense femtosecond laser pulses with solid targets is a topic that has attracted large interest in science and applications. For many of the related experiments a large energy deposition or absorption and an efficient coupling to XUV- and/or X-ray photons and/or high energy particles is important. Here, beside improvements in laser pulse properties also those of the target are relevant. The present work investigates the formation of laser-induced periodic surface structures on massive metal targets by femtosecond laser pulses in vacuum. The experimental results and the ripple formation mechanisms have been analysed and interpreted with newly developed theoretical models. The present results contribute to a simple optimization of targets by nano-structuring their surface in-situ which leads to a significantly enhanced absorption and conversion efficiency into XUV emission, X-rays and/or high energy electrons and protons after irradiation with a subsequent intense laser pulse.



11:45am - 12:00pm

Targeting mass production of nano/micro textured surfaces by USP laser: the New Skin project

Girolamo Mincuzzi, Alexandra Bourtereau, Marc Faucon, Laura Gemini, Simon Nourry, Aurélien Sikora, Rainer Kling

Alphanov, Aquitaine Institute of Optic - Rue F. Mitterand 33400 Talence (France)

Ultra-Short Pulse laser texturing (USP-LT) is a key technology for functionalisation of materials surface. Although the texturing of ≈1m2 surfaces have been successfully shown, extend USP-LT over several m2 surfaces represents an issue due to the need of high P, and a difficult process control. The “New Skin” project could represent a turning point pushing the readiness of USP-LT with a significant up-scale of the production volume.
Here we show the preliminary results obtained with the implementation of a demonstrative pilot line based on a 350 W, fs laser and a polygon scanner. We report the optimisation of the structures morphology on steel when P exceeds few hundreds of watts as well as the impact of the repetition rate (up to 10 MHz) and the hatch. A roll-to-roll approach is proposed jointly with an in-line monitoring system based on scatterometry. Finally, possible applications and values propositions are introduced and discussed.



12:00pm - 12:15pm

In-line monitoring of submicron laser texturing: a test bench for scatterometry

Aurélien Sikora, Girolamo Mincuzzi, Rainer Kling

ALPhANOV, France

Laser Induced Periodic Surface Structures (LIPSSs) with a submicronic periodicity induce a variety of surface properties (iridescence, hydrophobicity, antibacterial, etc.). In-line monitoring of LIPSS dimensions is challenging since the resolution of optical based microscopy techniques is insufficient or unable to withstand with harsh, industrial environment. These issues can be overcome using indirect measurement techniques such as scatterometry. It makes possible an indirect measurement of LIPSS morphology by analysing the reflection and/or diffraction pattern of an incoming light having a known spectrum and polarisation. We show that by using a proper configuration, scatterometry is barely sensitive to vibrations and fast enough for in-line monitoring fitting industrial requirements. In the frame of the NewSkin H2020 project, a scatterometer has been integrated and tested in a roll-to-roll machine including a fast polygon scanner (up to 200 m/s) and a 350 W femtosecond laser targeting mass production of LIPSS for antibacterial stainless steel.



12:15pm - 12:30pm

Effects of various misalignments and beam impurities on creation of optical needle using Pancharatnam-Berry phase elements

Pavel Gotovski1,2, Paulius Slevas1,3, Sergej Orlov1, Orestas Ulsinas1,3, Antanas Urbas1,3

1Center for Physical Sciences and Technology, Vilnius University, Lithuania; 2Vilnius Gediminas Technical University, Faculty of Electronics, Lithuania; 3Workshop of Photonics

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1:30pm - 2:30pmMicro: Surface Functionalization 3
Location: Room 4
Session Chair: Dr. Stephan Roth, Bayerisches Laserzentrum GmbH (blz), Germany
Room 4 
 
1:30pm - 1:45pm

Enhanced forming behavior of conditioning lines by inserted microstructures for the production of 3D waveguides

Alexander Wienke1, Mohd Khairulamzari Hamjah2, Gerd-Albert Hoffmann1, Jürgen Koch1, Peter Jäschke1, Jörg Franke2, Ludger Overmeyer1, Stefan Kaierle1

1Laser Zentrum Hannover e.V., Germany; 2Institute for Factory Automation and Production Systems, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany

In today's increasingly connected world, more and more data is being produced and processed. To meet these challenges, the OPTAVER research group is conducting research on an innovative manufacturing process for 3D waveguides. In this process, so-called conditioning lines are first applied to a PMMA substrate by means of flexographic printing. Between those the waveguide is applied by aerosol-jet in a subsequent process. If the degree of forming is too high, the conditioning lines crack and become unusable, since material accumulation of the waveguide material leads to strong scattering and high attenuation of the waveguides. By inserting microstructures in the flexographic printing form at points where a high degree of forming is to be expected, material voids occur in the printing. These act as a predetermined breaking point, leaving the critical areas of the conditioning line untouched. This can significantly increase the 3D capability, as demonstrated in forming tests.



1:45pm - 2:00pm

Femtosecond laser structuring of nodular cast iron for anti-corrosion and thermally stable superhydrophobic surface

Dhiraj Kumar, Gerhard Liedl

Institute of Production Engineering and Photonics Technologies, TU Wien, Austria

The superhydrophobic surface has many applications, such as anti-corrosion, anti-icing, and self-cleaning. In this paper, we describe superhydrophobic surfaces on nodular cast iron produced by femtosecond laser pulses. A rapid transformation of surface characteristics from hydrophilic to superhydrophobic has been achieved after placing the samples in a high vacuum chamber for 10 hours, indicating a significant reduction in the storage time required to develop hydrophobic properties. Thermal stability has been assessed after heating the samples at different temperatures for an hour in a furnace. Consequently, the static contact angle has been measured after cooling at room temperature. Samples irradiated at 0.63 J/cm2 and 3.18 J/cm2 with hatch distance of 20 µm show stable superhydrophobic characteristics up to 180°C. Corrosion tests have also been carried out on untreated and lasertreated samples at room condition in a 3.5% NaCl solution. Results indicate that a superhydrophobic surface has better resistance toward corrosion.



2:00pm - 2:15pm

Structural coloration and wettability control of stainless steel by a DLIP process

Tamara Delgado, Clovis Alleaume, Sara M. Vidal, Francisco J. Gontad, Félix Ares, Pablo Romero, Nerea Otero

AIMEN - Laser Centre, Spain

We present the use of a Direct Laser Interference Patterning (DLIP) process to modify both optical and wettability properties of stainless steel. A picosecond (30 ps) pulsed Ytterbium fiber laser operating at its fundamental wavelength (1030 nm) was combined with a DLIP setup based on the use of a Michelson interferometer. A line-like pattern with a 6 µm spatial period and a good intensity contrast was produced by the interference of two beams. Thus, line-like periodic microstructures were engraved on the surface of stainless steel samples by a laser surface texturing process. Through the modification of the surface topography, both structural coloration and wettability control were achieved.



2:15pm - 2:30pm

Superhydrophobic surfaces using ultra-short pulse structuring of thin metal layers

Fabian Schäfer, Simon Ruck, Max-Jonathan Kleefoot, Wadim Schulz, Florian Köhn, Joachim Albrecht, Harald Riegel

Aalen University, Germany

Fabrication of superhydrophobic surfaces induced by ultra short pulse lasers is a hotspot of surface studies. We report a way of generating superhydrophobic surfaces on stainles steel (304S15). The method for fabricating this water-repellant surfaces is to microstructure by irridating with ultra short pulses. Contact angle measurements were used to investigate the wettability of the surface in relation to the laser parameters (laser fluence and scan line separation). The steady conctact angle was investigated in the range of 140°.

Investigations with optical measuring methods (white light interferometer, light microscope) could be confirmed by scanning electron images. The generated surface shows hierarchical structures with nano and micro roughness similar to a lotus leaf. In further experiments, different materials shall be sputtered to obtain a thin stainless steel surface. Subsequent laser structuring should produce a functional surface with water repellent properties

 
2:45pm - 4:00pmMicro: Surface Functionalization 4
Location: Room 4
Session Chair: Clemens Roider, Institute of Photonic Technologies (LPT), Germany
Room 4 
 
2:45pm - 3:00pm

High-rate laser machining for large-area and high-throughput surface profiling and functionalization

Joerg Schille, Stefan Mauersberger, Andreas Gruner, Lutz Schneider, Kristian Kujawa, Udo Loeschner

University of Applied Sciences Mittweida, Germany

High-rate laser machining will be introduced as key technology for large-area surface texturing and bio-inspired functionalization. In fact, the polygon-mirror based scan technique allowing high-precision laser beam raster-scanning at hundreds meters per second is the core feature to bring high optical powers from kilowatt class lasers to industrial production. This is favourable for power scaling in micro machining as processing rate and throughput scale-up with higher pulse repetition frequency and laser powers. The great advantage of ultrafast beam movements is that unfavourable effects can easily be avoided, such as high thermal loads to the substrates and subsequent material melting as well as laser beam shielding by interactions with the previously induced plasma/particle plume. Inspired by sharks´ skin, this will be demonstrated by the example of riblet-like surface profiles and their replications in plastic materials thus providing a high potential for drag reduction in turbulent flows in technical applications.



3:00pm - 3:15pm

Laser polishing of laser micro weld seams on Cu-ETP and CuSn6 with green laser radiation

Moritz Küpper1, Marc Hummel1, Rakesh Kumar Pandey2, Constantin Häfner1

1RWTH Aachen University, Germany; 2Politecnico di Milano, Italy

Copper and copper alloys used for example in electrical applications can be contacted by laser micro welding. The achievable roughness of these micro weld seams can be too large for some applications (like sealing surfaces or to minimize surface oxidation). Up to now laser polishing, which smoothens the surface due to surface tension in the molten state, of copper could not be demonstrated successfully with industry common infrared high power laser systems typically used for laser polishing. This study investigates the use of green 515 nm wavelength high power laser sources for laser polishing of pure copper (Cu-ETP) and a widely used copper alloy (CuSn6). A suitable process window is identified by variation of process parameters (laser beam diameter, scanning speed, laser power) for single and overlapping remelting tracks. The best parameters are tested on laser micro weld seams created with the same setup to smoothen their rough surface.



3:15pm - 3:30pm

Laser texturing of heat exchanger tubes for nucleate boiling regime promotion

Félix Ares1, Ivette Coto1, Tamara Delgado1, Francisco Gontad1, Roberto Eiró2, Sara Vidal1, Nerea Otero1, Pablo Romero1

1AIMEN, Spain; 2INTEGASA, Spain

Titanium tubes of 16 mm diameter and 0.8 mm thickness, were textured using a CW, single mode, 1070 nm fibre laser. The laser beam was guided by a galvanometer scanner. Textures of homogeneous, parallel grooves of 60-80 µm width and 70-110 µm depth were generated on the exterior tubular surface. A wide range of parameters: laser power, laser speed, tube rotating speed or focal distance was studied to improve the homogeneity of the generated textures. These tubes were later tested in both controlled and industrial environments, along with non textured tubes, and their heat transfer behaviour was analysed under an ammonia nucleate boiling regime. Results indicate that laser textured tubes show a consistent increase of 60% of their heat transfer coefficient, when compared to original smooth tubes. These results prove that laser texturing is a suitable technique to significantly increase performance of heat exchangers that work under nucleate boiling regime



3:30pm - 3:45pm

Ultrashort laser coloration on titanium coatings

Eva Rodríguez Vidal1, Goretti Alberdi1, Borja Coto1, Oihane Hernandez1, Beatriz Diaz1, Aleix Ribera2

1TEKNIKER, Polo Tecnológico de Eibar, Calle Iñaki Goenaga 5, 20600, Gipuzcoa, Spain; 2INVESTPLASMA, Polígono Industrial Riu Sec, 105, 1, 12190 Borriol, Castellón, Spain

This study reports on the fabrication of structural and intrinsic colors from the oxide layers via ultrashort laser pulses on titanium coatings deposited on glass substrate. Surface modifications are tuned by adjusting laser parameters of wavelength, pulse length, scanning speed and energy per pulse. Two thickness (up to 1µm) of titanium coatings were deposited on glass substrates by physical vapor deposition. A comprehensive study of the physical and chemical measurements leading to the different appearances is presented. Different physical modifications, at micro and nanoscale levels, were identified depending on laser processing conditions. Quantitative analysis regarding chromaticity coordinates of the generated colors as well as phase composition of oxide layers were characterized by spectrophotometer and x-ray diffraction, respectively. Uniform and repetitive color palette on titanium coatings was developed by ultrashort laser processing.



3:45pm - 4:00pm

Direct laser-writing of metal nanostructures from the gas phase by two-photon absorption process

Nicolai Schwarz1,2, Michael Bassler1, Thomas Walther2, Thomas Klotzbuecher1

1Fraunhofer-Institut für Mikrotechnik und Mikrosysteme IMM, Mainz, Germany; 2Institut für Angewandte Physik, Technische Universität Darmstadt, Darmstadt, Germany

The fabrication of metallic 3D-nanostructures has received a lot of attention through new applications in plasmonics, e.g. metamaterials with a negative refractive index for optical cloaking and non-diffraction-limited optics. A new approach for the generation of three-dimensional metal nanostructures is introduced, based on two-photon-absorption of fs-laser radiation on silver-precursor molecules in the gas phase. A process chamber has been set up, allowing for evaporating a liquid organometallic silver-precursor under controlled temperature and pressure conditions. An inverse microscope objective of NA=0.65 and a working distance of 0.57 mm is used to focus the beam. The focus is moved in space by means of piezo-driven stage with nm-resolution. First two-dimensional structures with dimensions in the sub-micrometer range, are successfully deposited from the gas phase on glass substrates. The deposition parameters with respect to pressure, temperature and laser power, are going to be optimized to reach nm-resolution in structure size and building up 3D structures.

 

 
Date: Thursday, 24/June/2021
10:00am - 11:00amFundamentals and Process Simulation
Location: Room 4
Session Chair: Dr. Klaus Schricker, Technische Universität Ilmenau, Germany
Room 4 
 
10:00am - 10:15am

Corrosion resistant blackmarking via numerical modeling and simulation

Urs Eppelt, Daniel Seitz, Jörg Ziegler

Coherent Munich, Germany

Classical Laser Blackmarking with USP laser sources is a well-established process that is commercially available nowadays since a few years. This is especially true for its wide use on stainless steel supplies of the medical industry. Surprisingly, other industries (like household and consumer products industries) have even higher requirements on wear behavior (like corrosion resistance) than the medical industry with its strict approval procedures.

With the help of mathematical modeling and numerical simulation we wanted to understand the in-depth reasons for the limitations of classical blackmarking and develop a new laser marking process that could also fulfill the demands for acid resistance on products like white goods, sanitary fittings or automotive accessories which have not yet been opened up for this kind of laser process. We describe our success in modeling and simulation as well as process development in that field which is then evaluated by corrosion testing procedures.



10:15am - 10:30am

Estimating heat accumulation upon ultrafast laser irradiation

Liliana Cangueiro1, Thomas Kiedrowski2, Nikolaï Schroeder3, David Bruneel1, Andrés Lasagni3, J.A. Ramos-de-Campos1

1LASEA, Belgium; 2Robert Bosch GmbH; 3Institut für Fertigungstechnik Technische, Universität Dresden

Ultrafast lasers micromachining results depend both on the processing parameters and the material properties. The obtained thermal effects are negligible if a good combination of processing parameters is chosen. However, optimizing the processing parameters leading to the required surface quality on a given material can be quite complex and time consuming. Within the framework of the European project LAMpAS, we developed a model to estimate the heat accumulation on a surface as a function of the laser fluence, scanning speed and line pitch. The simulation results were correlated with experimental ones on different materials. The predictions of the model allow evaluating the heat distribution on the surface, as well as optimizing the ultrafast laser micromachining strategy yielding negligible thermal damage.



10:30am - 10:45am

Experimental setup for determination of absorption coefficient of laser radiation in molten metals as a function of temperature and angle

Tjorben Bokelmann1, Marius Lammers1, Jörg Hermsdorf1, Sobhan Emadmostoufi2, Oleg Mokrov2, Rahul Sharma2, Uwe Reisgen2, Stefan Kaierle1

1Laser Zentrum Hannover e.V., Germany; 2Welding and Joining Institute, RWTH Aachen University, Germany

For the process development of laser assisted double wire welding with nontransferred arc (LDNA), the simulation of the molten pool and its interaction with the laser radiation is of great importance. Therefore, an experimental setup for the determination of the temperature and angle dependent absorption coefficient of laser radiation in molten metals such as stainless steel and aluminum will be presented. A Yb:YAG disc laser with 1030 nm and a 940-1020 nm diode laser are used as laser beam sources. The stationary molten metal is inductively warmed and superheated by the laser beam with approximately 300-1000 W, whose radiation profile is shaped by homogenizing optics and ensures equal intensity when the angle is adjusted.

 
11:15am - 12:30pmMicro: Surface Functionalization 5
Location: Room 4
Session Chair: Dr. Stephan Roth, Bayerisches Laserzentrum GmbH (blz), Germany
Room 4 
 
11:15am - 11:30am

Improved thermal joining of aluminum and aluminum-polymer composites for battery applications through laser surface structuring

Christian Geiger, Lucas Hille, Célestine Singer, Michael F. Zaeh

Institute for Machine Tools and Industrial Management (iwb), Technical University of Munich, Boltzmannstr. 15, 85748 Garching, Germany

Lithium-ion batteries are the main electrochemical energy storage solution for electromobility applications because of their advantageous characteristics compared to other battery technologies. Currently, three cell designs (prismatic hardcase, prismatic pouch and cylindrical cells) with specific advantages and disadvantages are present in the market. Novel cell concepts aim to combine the strengths. For example, the good mechanical stability of hardcase cells should be merged with the high gravimetric energy density of pouch cells. Therefore, a laser structuring process is presented, which significantly improves the adhesion between aluminum-polymer composite foils and solid aluminum during thermal joining. Microscopic structures were formed on the aluminum surface by nano-second laser pulses. The results of a laser parameter study were analyzed by optical means (laser scanning microscopy and scanning electron microscopy) and in terms of adhesion strengths between the components. In conclusion, strategies and recommendations for the laser structuring process are derived.



11:30am - 11:45am

Laser-assisted selective fabrication of copper traces on polymers by electroplating

Vitalij Fiodorov1, Gediminas Račiukaitis1, Karolis Ratautas1, Zenius Mockus2

1Center for Physical Sciences and Technology, Department of Laser Technologies, Vilnius, Lithuania; 2Center for Physical Sciences and Technology, Department of Chemical Engineering and Technology, Vilnius, Lithuania

The paper reports a facile and low-cost laser-assisted method for selective deposition of copper traces on polymer surfaces. The technique uses a laser for selective polymer surface modification. The electrical conductivity of some polymers could be increased due to laser irradiation. Kapton PI film was used in our experiment. Samples were patterned using a picosecond laser at 1064 nm wavelength. The experiments were performed using average powers ranging from 4 to 8.5 W in 0.5 W increments, pulse repetition rates from 10 to 100 kHz and a constant scan rate of 100 mm/s. The sheet resistance was measured using the four-probe method, and it was reduced to < 50 Ω per square after laser patterning. Afterwards, the modified surface was metal deposited by electroplating.

Selective deposition of copper on polymers could be used in flexible electronic devices. This technology shows a huge potential in many fields: consumable electronics, automotive, etc.



11:45am - 12:00pm

Manufacturing of functional surfaces by replicating glass moulds structured by multiphoton polymerization

Sara María Vidal Álvarez, Nerea Otero Ramudo, Felix Ares Blanco, Maria Ivette Coto Moretti, Francisco José Gontad Fariña, Tamara Delgado García, Pablo Romero Romero

AIMEN Technology Centre, Spain

The present work deals with the fabrication of very low aspect ratio microstructures generated by Multi-Photon Polymerization (MPP) on glass substrates for their further use as good quality and high resolution replication moulds for optoelectronic devices. A commercial UV-curable resin from the ORMOCER® family was employed for the fabrication of the polymeric microstructures on two different substrates: glass and sapphire. These microstructures were replicated by injection moulding on polymeric components with an area of several cm2. The results of this work indicate that high resolution moulds can be fabricated through MPP, favouring the fabrication of high-quality replications. Additionally, the microstructures are proven to be resistant to their use through multiple replications. In fact, the topographical characterizations of the first and last replicas show similar characteristics, proving the reliability MPP for the fabrication of high quality moulds.



12:00pm - 12:15pm

Improved catalytic activity and surface functionalization of nanoparticles by pulsed laser-post processing of colloids.

Sven Reichenberger, Swen Zerebecki, Stephan Barcikowski

University of Duisburg-Essen, Germany

The presented talk intends to cover advances in laser-based post-processing of colloidal nanoparticles by laser fragmentation and -defect engineering for catalyst development. First, a new setup which provides a 100 µm thick flat liquid jet for laser post-processing of nanoparticles and favors a 10 times lower laser intensity deviation compared to the conventional cylindrical liquid jet will be presented. Due to the uniform laser intensity in the flat liquid jet, colloidal 3 nm gold nanoparticles with narrow size distribution (PDI < 0.1) were gained. In the second part of the talk, recent advances on laser-based defect engineering and related surface functionalization will be presented at the example of cobalt-spinel-based catalysts. It will be shown, that the catalytic activity is significantly improved especially when less than 3 laser pulses are employed per nanoparticle. In this context, laser-based surface doping and favorable process scalability will be discussed.



12:15pm - 12:30pm

Metallic surface functionalization by femtosecond laser beam shaping and LIPSS for industrial applications

Jérôme Patars, Liliana Cangueiro, David Bruneel, J. A. Ramos-de-Campos

Lasea, Belgium

Literature demonstrated the advantages of surface nanoscale texturation in many industrial applications, including batteries, medical implants and linear encoders. The next step is to find a cost-effective and non-invasive solution to replace actual material deposition and tooling techniques at industrial scale.

In the scope of the LASER4SURF project, we developed a new automated workstation enabling fast texturing of large surface samples (i.e. A4 format), using state of the art beam shaping techniques involving DOE and SLM combined with LIPSS generation to increase functionalization performances of the textured materials.

A key part of the workstation is its ability to automatically determine optimal laser processing parameters based on preliminary study done on any other laser processing device.

We also demonstrate that LIPSS texturation increases battery collectors charging capabilities, as well as their lifetime. We also demonstrate better bio-integration of medical implant for the human body, as well as increased accuracy linear encoders.

 
1:30pm - 2:30pmMicro: Surface Functionalization 6
Location: Room 4
Session Chair: Florian Huber, Institute of Photonic Technologies (LPT), Germany
Room 4 
 
1:30pm - 1:45pm

Friction reduction of stainless steel surfaces by laser microstructuring

Niklas Berger1, Benjamin Keim2, Munehiro Chijiiwa1, Hicham Derouach1, Senta Schauer2, Mareike Schäfer Schäfer1, Johannes A. L'huilier1

1Photonik-Zentrum Kaiserslautern e. V. (PZKL), Germany; 2EPflex Feinwerktechnik GmbH, Germany

Recently, friction reduction has become important in a wide range of technical applications. One limiting factor is the abrasion of two surfaces when they are moved against each other, causing friction losses. To overcome this, a functional optimization is necessary and thus the effectiveness of components will be increased by structuring the surfaces. Our approach is to introduce a dimple structure by laser microstructuring into the surface and thus significantly reduce the friction. In order to avoid burr around these dimples it is necessary to operate good heat management. For this reason, we carried out experiments using a USP laser with a pulse duration of 10 ps. Dimples with a diameter of 10 - 30 micrometers were made and systematic investigations were carried out by changing the depth and the arrangement of the dimples. By optimizing these parameters, friction could be reduced by 30 % compared to an unstructured surface.



1:45pm - 2:00pm

Impact of confined laser plasma plumes on the formation of LIPSS structures on stainless steel 316L

Anupam Ghosal1, Olivier Allegre1, Zhu Liu1, Gordon Jones2

1The University of Manchester, United Kingdom; 2Waters Plc, United Kingdom

Laser-induced periodic surface structures (LIPSS) has been used for functionalisation of the surface. Hence, the control of the formation of the LIPSS structures is considered an important feature. In this work, picosecond pulsed laser irradiation (wavelength 355nm, pulse duration 10ps, frequency 404.7 kHz) were performed on stainless steel 316L under the conditions of confined laser plasma plumes in an air environment. The plasma plumes generated due to laser-metal interaction were confined by covering the metal surface with a transparent glass plate at varying distances (Δz = 0, 150, 300, 450, 900 μm). The impact of the gap between metal and glass surface, towards the formation of uniform high-spatial-frequency-LIPSS (HSFL) was studied experimentally. Additionally, low-spatial-frequency-LIPSS (LSFL) was observed at higher fluence along with scattered metal deposits on the surface. This work demonstrated the possibility of creating uniform HSFL using confined laser plasma plumes as the impacting medium.



2:00pm - 2:15pm

Surface carbon enrichment of stainless steel using nanosecond pulsed laser surface alloying of graphite based coating

Hasib Mustafa, Matthias Feinaeugle, G.R.B.E. Römer

Chair of Laser Processing, Department of Mechanics of Solids, Surfaces & Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE, Enschede, the Netherlands

Laser surface alloying is a promising technique for modifying and/or improving surface properties of forming tools used in the fabrication thermoplastic composite parts. In this article, the results of a study on laser surface alloying of graphite based coatings on ferritic stainless steel using a nanosecond laser source is presented. The effect of different laser processing parameters and coating types on the laser-induced carbon diffusion are analyzed. The morphology of the processed areas was characterized using confocal microscopy and scanning electron microscopy. The atomic concentration of diffused carbon was determined using energy-dispersive X-ray spectroscopy. It was found that the surface carbon content of stainless steel can be increased substantially up to 70%. Cross-sectional analysis revealed the dependence of diffusion thickness on accumulated laser fluence, having a maximum at 6 µm. In comparison with low and high carbon steel, and unprocessed stainless steel, laser processed samples demonstrated improved wear properties.



2:15pm - 2:30pm

The effect of chemical components on wettability at ps laser micromachined surface on stainless steel 304

Munehiro Chijiiwa1, Niklas Berger1, Mareike Schäfer1, Rolf Merz2, Michael Kopnarski2, Peter Mitschang3, Johannes A. L'huillier1

1Photonik-Zentrum Kaiserslautern e.V., 67633 Kaiserslautern, Germany and Research Center OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany; 2Institute of Surface and Thin Film Analytics, IFOS, Research Center OPTIMAS, TU Kaiserslautern, 67663 Kaiserslautern, Germany; 3IVW—Institute for Composite Materials GmbH, Manufacturing Science, 67663 Kaiserslautern, Germany

Recently, controlling the wettability of metallic surfaces by laser micromachining has become important for many technical applications. However, there is still a challenge in understanding chemical effects on contact angle (CA) since there is even a big gap in knowledge of the laser micromachining’s influence on the surface chemistry. In this study, the relationship between the local surface chemistry at ps laser micromachined surfaces on stainless steel 304 and CA was discussed by using a new model description, based on a multiple regression analysis. The proposed model was verified by using experimental wetting behavior of different kinds of liquid and surface chemistry, characterized by XPS spectroscopy. To have a variety of different wettability of the samples, different structures, storage conditions, and post processes were tested. As a result, our proposed model showed a nice correlation between predicted CA from chemical components and measured CA.

 
2:45pm - 4:00pmMicro: Surface Functionalization 7
Location: Room 4
Session Chair: Dr. Stephan Roth, Bayerisches Laserzentrum GmbH (blz), Germany
Room 4 
 
2:45pm - 3:00pm

Improvement of hardness and wear-resistance of direct laser interference patterned bearing steel surface using laser surface heating approach

Mikhael El-Khoury1, Marko Seifert2, Sven Bretschneider2, Martin Zawischa2, Tim Kunze2, Andrés Fabián Lasagni1,2

1Institut für Fertigungstechnik, Technische Universität Dresden, George-Bähr-Str. 3c, 01069 Dresden, Germany; 2Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS, Winterbergstr. 28, 01277 Dresden, Germany

Direct Laser Interference Patterning (DLIP) has emerged as a practical technology to enhance surface functionality, for instance, to improve tribological properties of steel parts. In fact, the life of tribo-pairs with enhanced tribological properties is related to the durability of those microstructured patterns that can be significantly improved by increasing their hardness. In this study, we report on the laser heat treatment of periodic topographies produced on bearing steel plates using DLIP technology. The hardening treatment allowed to tune the surface hardness from 210 HV to 827 HV. The combination of the patterning and laser hardening approaches permitted to improve the wear-resistance of the structured surface by ~ 50 % at contact point pressure of ~17.87 GPa. The outcomes indicated that by applying the proposed joined methodology it is conceivable to hold the higher hardness of the bearing steel plates and simultaneously to keep intact surface microstructures.



3:00pm - 3:15pm

Laser melt injection for homogenous particle distribution in copper materials

Anika Langebeck, Annika Bohlen, Thomas Seefeld

BIAS - Bremer Institut fuer angewandte Strahltechnik GmbH, Germany

MMC (metal matrix composite) layers have great potential to improve abrasive wear resistance of tool surfaces such as injection molds. For this, laser melt injection is used to disperse hard particles into the molten tool surfaces.

Injection molding tools are often made of copper materials which are characterized by a high thermal conductivity and have low absorptivity for the wavelength of a disk laser (1030 nm). This makes coupling into the material and thus a stable process more difficult. In this work coupling is improved by increasing the laser power density. In combination with beam modulation a large melt pool can be generated. It can be demonstrated that low process velocities are mandatory for a homogenous particle distribution. For the analyzed MMC system of aluminum bronze reinforced with tungsten carbide, a welding speed of 300 mm/min leads to a homogenous distribution whereas faster process velocities result in a graded particle distribution.



3:15pm - 3:30pm

Laser-based coating process of PA12 on stainless steel substrates

Alexander Wittmann1,3, Oliver Hentschel1,3, Jakob Ermer2,3, Alexander Sommereyns1,3, Florian Huber1,3, Michael Schmidt1,2,3

1Institute of Photonic Technologies (LPT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Konrad-Zuse-Straße 3/5, 91052 Erlangen, Germany; 2Bayerisches Laserzentrum GmbH (blz), Konrad-Zuse-Straße 2/6, 91052 Erlangen, Germany; 3Erlangen Graduate School in Advanced Optical Technologies (SAOT), Paul-Gordan-Straße 6, 91052 Erlangen, Germany

Thermoplastic coatings are of great interest for multiple applications in industry e.g. to protect the surface from corrosion and to prevent excessive wear. In the present study a laser-based coating process for PA12 powder on stainless steel substrates is investigated. To evaluate the influence of the wavelength on the resulting coating characteristics, ytterbium (λ=1.07 µm) and thulium fiber laser (λ=1.94 µm) are used to consolidate the manually deposited PA12 powder. In addition, the effects of substrate preheating on substrate adhesion are examined. The specimens are analyzed by optical and confocal laser scanning microscopy. Furthermore, powder material and coatings are characterized by differential scanning calorimetry. Results show that dense and adherent coatings can be applied on stainless steel substrates. Coatings melted by ytterbium fiber laser exhibit a lower degree of particle melting. In case of thulium fiber laser, the adhesion is further increased by additional substrate preheating.



3:30pm - 3:45pm

Processing of an organosilazane-based glass/ZrO2 composite coating system by laser pyrolysis

Alexander Horcher1, Katja Tangermann-Gerk2, Walter Krenkel1, Günter Motz1

1Universität Bayreuth, Germany; 2Bayerisches Laserzentrum Erlangen, Germany

Protective ceramic-based coatings are frequently the most suitable and cost-effective solutions for problems like corrosion, oxidation and wear. It has been shown, that the polymer-derived ceramics technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace. However, the required high temperatures for the preparation of the ceramic coatings only allow the use of temperature-resistant substrates. A very innovative approach to overcome this restriction is the use of laser radiation as an energy source for the pyrolysis of the preceramic polymer. For this reason, a composite coating system composed of an organosilazane with ZrO2 and glass particles as fillers was developed suitable for pyrolysis with a Nd:YAG laser. The composite coating slurry was applied onto stainless steel substrates by spraying and afterwards irradiated with a Nd:YAG laser. Finally, the microstructure, chemical composition, abrasions resistance as well as the mechanical properties and the corrosion behavior was investigated.



3:45pm - 4:00pm

Laser sintering of ceramic-based solid-state battery materials

Linda Hoff

Fraunhofer Institute for Laser Technology (ILT), Germany

Ceramic solid-state batteries can increase gravimetric energy density and safety compared to conventional lithium-ion batteries. The ceramic materials are applied to a metallic carrier foil by screen printing and then thermally post treated (dried and sintered) to produce adhesive layers with the highest possible density.

Disadvantages of conventional oven processes are the possible diffusion between adjacent layers due to long process times (in the range of minutes) at high temperatures. Furthermore, multilayer systems, containing different materials with varying decomposition temperatures, cannot be treated successfully.

Laser processing shows potential for reducing diffusion processes and preservation the materials crystal structure (meaning preserving their electrochemical properties) due to short interaction times within the range of seconds. In this work, the laser sintering of ceramic micro particle battery layers is presented, addressing the challenges of reaching a rather homogeneous temperature profile across the coating thickness within short processing times while preserving the materials integrity.