Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 27th Jan 2022, 10:34:19pm CET

Program for LiM 2021
Date: Thursday, 24/June/2021
10:00am - 11:00amMacro: Surface Treatment
Location: Room 1
Session Chair: Daniel Holder, University of Stuttgart, Germany
Room 1 
10:00am - 10:15am

Effect of femtosecond laser shock peening on surface morphology and hardness of nickel titanium alloy

Hao Wang1, Evgeny L. Gurevich2, Andreas Ostendorf1

1Ruhr-Universität Bochum; 2Münster University of Applied Sciences

Nickel-titanium alloy (NiTi) has been widely used for the fabrication of microelectromechanical and body implants, so it is very important to enhance its surface mechanical property. Laser shock peening as a new and important surface treatment technique has been used to enhance the mechanical properties of different metal materials. Normally, the nanosecond laser with pulse-width between 5 ns and 20 ns is used to induce a high-pressure shock wave that can generate plastic deformation in the top layer of metals. In this paper, the surface morphology and hardness of NiTi alloy after femtosecond laser shock peening in the air are studied, which shows that the surface roughness and hardness increased after femtosecond laser treatment.

10:15am - 10:30am

Influence of multi-pass laser hardening on surface residual stress and distortion

Yang Lu1, Heiner Meyer2, Tim Radel1

1Bremer Institut für angewandte Strahltechnik GmbH; 2Leibniz-Institut für Werkstofforientierte Technologien

Laser hardening is used to harden the surface layer with minimal distortion and to induce residual compressive stress. Within the literature, the approach of increasing the hardness and hardening depth by multi-pass laser hardening based on accumulation effects is shown. Within this study, the effect of multi-pass laser hardening of normalized AISI 4140 on the surface residual stress and distortion is examined. The multi-pass laser hardening is carried out using a continuous wave laser with a rectangular beam shape using different process velocities and number of cycles without heat accumulation after each cycle. The results show that for a comparable hardening depth, there is less distortion at single pass hardening with low scanning speed compared to the multi-pass hardening with high scanning speed. These findings indicate that multi-pass laser hardening is therefore only preferable if technical limitations like the available laser power prevents the required hardening depth.

10:30am - 10:45am

Interaction between laser radiation and antifouling coating underwater

Stanislav Zimbelmann1, Benjamin Emde1, Jörg Hermsdorf1, Stefan Kaierle1, Tim Heusinger von Waldegge2, Dorothea Stübing2, Markus Baumann3

1Laser Zentrum Hannover e.V., Germany; 2Fraunhofer IFAM, Germany; 3Laserline GmbH, Germany

The biofouling on a ship´s hull has an enormous economic impact on its operation. Increasing biofouling leads to the introduction and spread of invasive species, a raised frictional drag in the water, an increased fuel consumption and thus an additional emission of greenhouse gases. In this context, the prevention or removal of biofouling becomes essential. Conventional, mechanical in-water-cleaning methods have several ecological and regulatory disadvantages. In the context of a laser-based underwater ship cleaning, that is currently under development, we investigated the interaction between laser radiation and a self-polishing copolymer (SPC) antifouling coating. Important process parameters were investigated to determine the laser power damage threshold of the SPC coating. These include the measurement of the reflection properties and the surface properties of the SPC coating.

10:45am - 11:00am

Laser cleaning as a productive surface post-treatment method for LPBF parts

Markus Hofele1,2, Johannes Neuer1, Malena Lindenberger-Ullrich1, Jochen Schanz1,2, David K. Harrison2, Anjali K. M. De Silva2, Harald Riegel2

1Aalen University, Germany; 2Glasgow Caledonian University, United Kingdom

Laser Powder Bed Fusion (LPBF) is the most common additive manufacturing technique for rapid prototyping and industrial manufacturing of complex individual metal parts. The LPBF process offers the opportunity to directly build solid metal parts with less geometric restrictions, low porosity and good mechanical properties. However, the surface of the parts exhibits a rough surface with massive powder contamination combined with a thick oxide layer on it. Laser cleaning provides the possibility of a contact-free and full-automatable surface treatment with high area rates.

This work deals with the investigation on laser cleaning of LPBF surfaces made of Aluminum AlSi10Mg. Laser cleaning with an nanosecond pulsed fiber laser by variation of the beam intensity, fluency and number of cleaning repetitions are investigated. Threshold beam intensities for the powder and oxide removal and base material ablation are determined. The ablation efficiency is analyzed by means of SEM, WLI and microscopic images.

10:00am - 11:00amAdditive Manufacturing: Directed Energy Deposition 3
Location: Room 2
Session Chair: Nicole Emminghaus, Laser Zentrum Hannover e.V., Germany
Room 2 
10:00am - 10:15am

Analysis and recycling of bronze grinding waste to produce maritime components using directed energy deposition

Vinzenz Müller1, Angelina Marko1, Tobias Kruse2, Max Biegler1, Michael Rethmeier1,3

1Fraunhofer Institute for Production Systems and Design Technology IPK, Germany; 2Mecklenburger Metallguss GmbH, Germany; 3Bundesanstalt für Materialforschung und -prüfung (BAM), Germany

Additive manufacturing promises a high potential for the maritime sector. Directed Energy Deposition (DED) in particular offers the opportunity to produce large-volume maritime components like propeller hubs or blades without the need of a costly casting process. The post processing of such components usually generates a large amount of aluminum bronze grinding waste. The aim of the presented project is to develop a sustainable circular AM process chain for maritime components by recycling aluminum bronze grinding waste to be used as raw material to manufacture ship propellers with a laser-powder DED process. In the present paper, the main challenges and promising measures and methods to recycle metallic grinding waste are shown. Two types of grinding waste are investigated using a CamSizer particle analysis system and compared to commercial DED powder. To be able to compare the material quality and to verify DED process parameters, semi-academic sample geometries are manufactured.

10:15am - 10:30am

Evaluation of steady state via thermography during laser and wire based directed energy deposition

Anton Emil Odermatt, Nikolai Kashaev

Helmholtz-Zentrum Geesthacht, Institute of Materials Mechanics, Department of Laser Processing and Structural Assessment

Additive manufacturing of structures in one continuous deposition process is appealing because defects at the start and end-points of a track are avoided. For the evaluation of process stability, a steady state process needs to be reached. A methodology for the determination of the interpass temperature for processes using a positioner for movement of the work piece has been developed. This methodology was applied to a laser and wire based directed energy deposition process. The approach of the steady state process can be described by an exponential growth law. From the interpass temperature a cooling rate can be calculated. The evolution of the interpass temperature can be used for process control and the cooling rate can be related to material properties. A comparison with results from the literature shows that the convergence rate is mainly dependent on the power level of the energy source and the size of the structure.

10:30am - 10:45am

Influence analysis of the layer orientation on mechanical and metallurgic characteristics of DED manufactured parts

Florian M. Dambietz1, Tobias S. Hartwich1, Julian Scholl-Corrêa2, Dieter Krause1, Peter Hoffmann2

1Hamburg University of Technology, PKT; 2ERLAS Erlanger Lasertechnik GmbH

With an increasing trend in product individualization, manufacturing custom-designed solutions and focusing on the explicit industry’s needs are crucial to the manufacturer’s success. Especially within high-tech industries such as aerospace industry, high-strength, large-sized but still lightweight metal parts are required. Although the Direct-Energy-Deposition (DED)-technology offers a proven outset point for targeting this issue, there are few material-, metallurgic-, process-, and geometry specific data available to support the initial design process of such parts. This contribution presents a profound study of different steel- and aluminium materials with respect to their metallurgic and mechanical characteristics. Using a state-of-the art DED-Laser system, tensile test specimens have been manufactured with alternative layer orientations. These specimens are analysed with regard to the required milling oversize, heat-induced stress deformation, metallurgic characteristics and their tensile characteristics. As a result of this investigation, a suitable baseline for the future generation of a DED design-by-feature catalogue is given.

10:45am - 11:00am

Investigation on laser cladding of rail steel without preheating

Christian Brunner-Schwer1, Max Biegler1, Michael Rethmeier3,1,2

1Fraunhofer Institute for Production Systems and Design Techology, Pascalstraße 8-9, 10587, Berlin, Germany; 2Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen, 87 12205, Berlin, Germany; 3Institute of Machine Tools and Factory Management, Technische Universität Berlin, Pascalstraße 8-9, 10587, Berlin, Germany

The contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Rails with a pearlitic microstructure have proven to provide the best wear resistance under severe wheel-rail interaction in heavyhaul application. High speed laser cladding, a state-of-the-art surface engineering technique, is a promising solution to repair damaged railheads. However, without appropriate preheating or processing strategies, these steel grades lead to martensite formation and cracking during deposition welding.

In this study, laser cladding of low-alloy steel at very high speeds were investigated, without preheating the railheads. Process speeds of up to 27 m/min and Laser power of 2 kW are used. The clad, heat affected zone and base material are examined for cracks and martensite formation by hardness tests and metallographic inspections. A methodology for process optimization is presented and the specimens are characterized for suitability.

10:00am - 11:00amAdditive Manufacturing: Medical Applications
Location: Room 3
Session Chair: Dr. Florian Klämpfl, Institute of Photonic Technologies (LPT), Germany
Room 3 
10:00am - 10:30am

Invited Talk: Selective laser sintering 3D printing of bespoke medications

Atheer Awad

University College London, United Kingdom

3D printing is a rapid manufacturing technology that has found promising applications in many fields, including pharmacy. In particular, laser-based technologies enable the creation of precise and intricate structures, potentially causing a paradigm shift in medicine design, manufacture and use. As an example, early-phase drug development (such as preclinical studies and first-in-human trials) could be expedited by using these technologies to rapidly produce formulations with excellent dose flexibility at low cost, on demand. Similarly, they could support formulation development because they have the capability to produce rapid product iterations for testing, such as excipient compatibility and drug release. Within hospitals and pharmacies, such technologies could accelerate the field of personalised medicine by moving treatment away from a ‘one size fits all approach’ towards personalisation. This presentation will give an overview on the use of a laser-based 3D printing technology and its promising applications, highlighting its potential in personalising medications.

10:30am - 10:45am

Laser directed energy deposition produces improved cp Ti for dental prosthetic applications

Óscar Barro1,2, Felipe Arias-González3, Fernando Lusquiños1,5, Rafael Comesaña4, Jesús del Val1, Antonio Riveiro4, Aida Badaoui4, Félix Gómez-Baño2, Juan Pou1,5

1CINTECX, University of Vigo, LaserON Research Group, Vigo, SPAIN; 2Corus-Fegoba, A Coruña, SPAIN; 3School of Dentistry, Universitat Internacional de Catalunya, Barcelona, SPAIN; 4Materials Engineering, Applied Mechanics and Construction Department, University of Vigo, Vigo, SPAIN; 5Galicia Sur Health Research Institute (IIS Galicia Sur), SERGAS-UVIGO, Vigo, SPAINin

Titanium and titanium alloys are widely employed in biomedical applications by virtue of their remarkable corrosion resistance, biocompatibility, exceptional specific strength and relatively low elastic modulus. Commercially pure titanium (cp-Ti) is a designation for titanium with reduced content of alloying elements, having a great resistance to corrosion and reduced cytotoxicity.

Laser directed energy deposition (LDED) is an additive manufacturing method able to produce metallic materials of great quality. By controlling the cooling rates, the material microstructure can be tuned in order to improve its mechanical/chemical properties. In the present work, LDED using a high power diode laser as energy source, was used to produce cp-Ti parts of grade 4. The cp-Ti obtained by LDED showed a higher mechanical performance than the commercial counterpart: 7% increment of ultimate tensile strength and 30% increment of toughness. These results can be attributed to a specific microstructure modification inherent to the LDED process.

10:45am - 11:00am

Additive manufacturing for minimally invasive endomicroscopy

Robert Kuschmierz, Elias Scharf, Jürgen Czarske

TU Dresden, Germany

Miniaturized flexible endoscopes employ coherent fiber bundles (CFB) to transfer intensity information by using lenses. This increases the footprint of the endoscope to several millimeters. Furthermore, the phase information of the light is distorted during transfer due to manufacturing errors of the CFB, which limits the endoscope to 2D imaging. Calibrating and compensating the phase distortion allows for lens less imaging. We present, the use of additive manufacturing to apply diffractive optical elements (DOE) onto the fiber facet for phase compensation. Using 2P-polymerization axial resolutions better than 20 nm can be achieved. This enables robust and cost efficient, endoscopes for 3D imaging. The influence of the DOE quality especially the axial resolution towards the image quality is discussed. With a total diameter below 400 µm, novel applications for instance for in-vivo cancer diagnostics in the brain can be envisioned.

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: Joining (Welding and Brazing)
Location: Room 1
Session Chair: Florian Kaufmann, Bayerisches Laserzentrum GmbH (blz), Germany
Room 1 
11:15am - 11:30am

OCT keyhole depth measurement in copper micro welding

Tobias Beck

Robert Bosch GmbH, Germany

The transition of the powertrain from combustion to electric systems increases the demand for reliable copper connections. For such applications, laser welding has become a key technology. Due to the complexity of laser welding, especially at micro welding with small weld seam dimensions and short process times, reliable in-line process monitoring has proven to be difficult. By using a green laser (515 nm), the welding process of copper benefits of the increased absorption, resulting in a shallow and stable deep penetration welding process. In this contribution, the monitoring of the capillary depth in micro copper welding, with welding depth of up to 1 mm, was performed coaxially, using an optical coherence system with a measurement wavelength of 840 nm. By comparing the measured capillary depth and the actual welding depth, independently of the investigated process parameters and the stability, a good correlation between two measured values could be shown.

11:30am - 11:45am

Determination of thermophysical process limitations for the laser-based droplet brazing process using different droplet and substrate materials

Jakob Ermer1,3, Florian Kohlmann1, Markus Müller1, Florian Kaufmann1, Stephan Roth1,3, Michael Schmidt1,2,3

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

The demand for microelectronic components is rising constantly over the last few decades due to the progress in digitalization. Along with this, the requirements for joining technologies are growing since they are highly responsible for progress in microelectronics. Laser-based droplet brazing shows unique features like a quasi-force-free joining process and high-temperature stable connections and is therefore on the way to its industrial implementation. While the first developments have been limited to the contacting of silver metallizations on piezo actuators, today the transferability of the process with regard to different solder and substrate materials is a major goal. In this work the relation between the solidification time of the droplet and diffusion processes depending on the substrate layout and material properties is investigated via highspeed imaging and EDX analysis. Based on the thermophysical behaviour of the process, the scalability for future applications can be derived for different material combinations.

11:45am - 12:00pm

Temporally and spatially highly resolved reconstruction of vapor capillary geometry during laser beam welding using synchrotron radiation

Marc Hummel1, André Häusler2, Sören Hollatz2, Christian Hagenlocher3, Jannik Lind3, Ulrich Halm4, Christoph Schöler4, Alexander Olowinsky2, Arnold Gillner1,2

1RWTH Aachen University, Chair for Laser Technology LLT, Germany; 2Fraunhofer Institute for Laser Technology LLT, Germany; 3University of Stuttgart, Institut für Strahlwerkzeuge IFSW, Germany; 4RWTH Aachen University, Nonlinear Dynamics of Laser Manufacturing Processes NLD, Germany

Welds of electrical components made of aluminum and copper need high electrical and mechanical quality. Process instabilities do not allow a continous reproducibility. To generate a deeper understanding of the process and to evaluate process dynamics, it is possible to use modern in situ analysis methods.

In this work, in situ phase-contrast high-speed videography using synchrotron radiation is presented. The phase contrast method reveals the phase boundaries between solid, liquid and gaseous phases. A spatial resolution down to <20 µm is possible due to the high coherence of the synchrotron beam, which allows to observe small vapor capillaries of fiber lasers with <100 µm diameter. 3D capillary geometries are reconstructed from 2D image data of welds on aluminum using a fiber laser and disc laser. Ray tracing is performed using this reconstruction, which allows the time resolved tracking of the laser beam inside the vapor capillary for quantitative estimations.

12:00pm - 12:15pm

Direct welding of glass and copper with a large gap by femtosecond laser pulse bursts

Qingfeng LI1, Gabor Matthäus1, Stefan Nolte1,2

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Straße 15, 07745 Jena, Germany; 2Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Center of Excellence in Photonics, Albert-Einstein-Straße 7, 07745 Jena, Germany

We report on the welding of borosilicate glass to copper using bursts of femtosecond laser pulses with a pulse duration of 265-fs and a wavelength of 1030-nm. The systematical analysis demonstrated in this paper represents a fundamental step towards the robust laser micro-welding of glass-to-metal.

The highest bonding strength is achieved with a laser fluence 2.5 times higher than the laser-induced damage threshold of the glass sample. Moreover, the glass-metal interface must be located within the Rayleigh range of the focused laser beam representing a focal diameter of 3.7-µm, and the gap size between both components must be less than 2-µm. The highest value, in the region of 14-MPa, compares well with proof-of-principle demonstrations published before. However, in contrast to previous achievements, no clamping is required. Consequently, the presented work demonstrates an easy glass-to-metal welding approach as an alternative to traditional bonding techniques based on adhesives or sample-pretreatments.

12:15pm - 12:30pm

Investigations on the influence of the material selection of the clamping device during laser transmission welding of multi-layer polymer films with wavelength-adapted laser beam sources

Maximilian Brosda, Phong Nguyen, Alexander Olowinsky, Arnold Gillner

Fraunhofer-Institut für Lasertechnik ILT, Germany

In lasertransmissionwelding process of polymers with wavelength adapted laser beam sources, the joining partners are fixed in an overlap arrangement. A sufficient energy absorption is ensured by addressing the material-dependent intrinsic absorption bands. The fixing is realized by a clamping device to achieve a technical zero gap between the joining partners in order to ensure heat exchange and melt permeation. The materials are in direct contact with the polymers and influence the heat dissipation as well as the propagation of the laser beam. While the upper material must be transparent for the laser radiation, a variety of materials are available for the lower part. Hence, it is investigated how the individual material combinations affect the process.To investigate the influence of material combinations as well as the influence of roll-to-roll processing or possible process limits welding tests are performed. The weld seam is analyzed by cross sections and tensile tests.

11:15am - 12:30pmAdditive Manufacturing: Powderbed, Copper
Location: Room 2
Session Chair: Dr. Stefan Kaierle, Laser Zentrum Hannover e.V., Germany
Room 2 
11:15am - 11:30am

Development of SLM 3D printing system using galvano scanner for pure copper additive manufacturing by 200W blue diode laser

Keisuke Takenaka1, Yuji Sato1, Koji Tojo2, Masahiro Tsukamoto1

1Joining and Welding Research Institute, Osaka University, Japan; 2Shimadzu Corporation, Japan

Selective laser melting (SLM) is one of laser additive manufacturing technologies. Because absorptance of blue light on pure copper materials is higher than that of conventional near-infrared light, a blue diode laser is expected to effective in shaping pure copper parts. In our previous study, we developed a high power and high intensity blue diode laser with the wavelength of 450 nm. Output power and fiber core diameter was 200 W and 100 µm, respectively. In this study, we have developed a SLM machine using galvano laser scanner with the 200 W blue diode laser. The laser power and the scanning speed were changed to form a pure copper parts in the SLM method, and the influence of them on the cross-sectional area of the parts was investigated.

11:30am - 11:45am

3D printing of high-density copper parts using common NIR CW laser systems at moderate powers

Hagen Kohl1, Lisa Schade1, Gabor Matthäus1, Tobias Ullsperger1, Burak Yürekli1, Brian Seyfarth1,2, Bernd Braun3, Stefan Nolte1,2

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Germany; 2Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Center of Excellence in Photonics, Germany; 3Nuremberg Institute of Technology Georg Simon Ohm, Germany

Additive manufacturing (AM) of pure copper using laser assisted powder bed fusion (LPBF) at a wavelength of 1070 nm is demonstrated. In comparison to established LPBF materials, pure copper exhibits an extremely high reflectivity for wavelengths around 1 µm and the highest thermal conductivity among other AM materials. Although, pure copper is one of the most interesting materials for AM, the interplay of these characteristics still prevents copper to be applied using common laser-based AM machines. In this work, we demonstrate a wide processing window for 3D-printing of high-density copper parts based on a fiber laser as widely used in common AM machines. These achievements were obtained with the help of a self-developed numerical model that guided our experimental studies during the LPBF process. After process optimization, relative densities over 99 % can be demonstrated without the help of intense preheating or post processing like hot isostatic pressing.

11:45am - 12:00pm

Energy coupling in laser powder bed fusion of copper using different laser wavelengths

Klaus Behler2, Daniel Heussen1, Marvin Kupper1, Nobert Pirch1, Tim Lantzsch1, Johannes Henrich Schleifenbaum3

1Fraunhofer-Institut für Lasertechnik ILT, Aachen, Germany; 2Technische Hochschule Mittelhessen, Friedberg, Germany; 3RWTH Aachen University Lehrstuhl für Digital Additive Production DAP

Highly conductive pure copper is crucial for high current applications in electrical and mechanical engineering. The additive manufacturing of components from pure copper using laser powder bed fusion (LPBF) with conventional machine technology and "infrared" laser radiation (λ ≈ 1070 nm) is challenging due to the high reflectivity of copper for infrared laser light. Fraunhofer ILT has been investigating possibilities to use lasers within the visible spectral range (green @ λ=515 nm and blue @ λ=450 nm) in the LPBF process. It has been shown that there is a potential to improve energy coupling and process stability applying such lasers in the LPBF process. In this paper calorimetric absorptivity measurements are presented, showing the influence of wavelength and process parameters as well as material conditions on the effective energy input for the melting of copper substrate material as well as of powder material.

12:00pm - 12:15pm

Laser powder bed fusion (L-PBF) of pure copper using a 1000 W green laser TruDisk

Guillaume Nordet1,2, Cyril Gorny1, Pierre Lapouge1, Albin Effernelli2, Etienne Blanchet2, Frederic Coste1, Patrice Peyre1

1PIMM Laboratory - ENSAM Paris; 2AddUp

Additive manufacturing of pure copper with lasers is complex using usual near IR laser wavelength, due to a high reflectance (~95 % at 1.07µm) combined with a high conductivity. This results in limited parts density, never exceeding 99%, whereas other metals can easily reach 99.9 % density. A possible way of improvement is to reduce the laser wavelength (from near IR to green) to enhance laser absorption and reduce the power needed to provide deep and stable tracks. In the current work, a detailed study was carried out with the use of a 1 kW cw green laser implemented on a L-PBF prototype. Two objectives were considered: (1) investigating the laser absorbance during single L-PBF tracks at various energy densities and welding regimes (conduction, keyhole) and (2) building various 3D parts and optimizing their density. Finally, parametric study allowed obtaining up to 99.9 % dense parts from pure copper powder.

12:15pm - 12:30pm

Additive manufacturing of conductive copper traces on 3D geometries by laser-sintering

Ejvind Olsen, Ludger Overmeyer

Leibniz Universität Hannover, Germany

These days, additive manufacturing processes cover an extensive range of materials. A new trend is a growing interest in the implementation of additional functions like electrical circuits. Combining full-surface primer and copper ink coating from printed electronics with laser processing enables integrating conductive traces directly on the surface of 3D-printed components. Priming reduces the roughness of the 3D printed (multi-jet modeling) circuit carrier below 100 nm. Afterward, the metal-containing ink is dip-coated, dried, and sintered locally by laser processing. The used laser system includes a focused and pulsed 1064 nm laser beam controlled by a scanner with three optical axes (x, y and z-direction). This research presents a detailed investigation on the influence of 3D geometrical factors like radii and sidewall angle on the resulting conductive trace resistance. Electron beam imaging technology with energy dispersive x-ray spectroscopy characterizes the conductive tracks regarding geometric and material properties.

11:15am - 12:30pmMicro: Innovations
Location: Room 3
Session Chair: Prof. Michael Schmidt, Institute of Photonic Technologies (LPT), Germany
Room 3 
11:15am - 11:45am

Invited Talk: Ultrashort pulsed laser micro processing: Multi-pulse and beam forming strategies for high throughput at high average powers

Beat Neuenschwander, Stefan M. Remund, Markus Gafner, Michalina W. Chaja

Bern University of Applied Sciences, Switzerland

The development of ultrashort pulsed laser systems actually goes far beyond the kW level. But e.g. for metals and single pulses todays standard methods like galvo scanners are not suited for higher average powers and alternative approaches have to be developed. We will get an insight into actual developments using multi-pulse strategies in temporal representation as pulse bursts and in spatial representation as multi-beams or with direct beam forming. A combination of these methods with synchronized scanning or real pulse on demand option could pave the way for using high average powers.

11:45am - 12:00pm

Excimer laser sintering of ceramic thin films for solid state batteries

Matthias Trenn1, Ralph Delmdahl2, Karsten Lange1

1Fraunhofer Institut für Lasertechnik ILT, Germany; 2Coherent LaserSystems GmbH & Co. KG, Göttingen

The geopolitical dependence on limited fossil resources and the increasing number of environmental disasters are enormous challenges for today’s society. An important element to overcome these essential problems is to increase the performance of energy storage systems and the efficiency of energy conversion devices. Promising solutions are solid state batteries and solid oxide fuel cells. Both cell systems demanding high standards on new production technologies. Temperature-sensitive thin film systems make conventional sintering processes impossible.
In the underlying investigation, a new highly scalable excimer laser-based sintering process of ceramic thin films is presented. The nanosecond pulses selectively melt surface the powder grains. Due to the 248 nm wavelength of the excimer laser, sintering depths of 3 - 8 µm can be achieved. In the process, the crystalline phase and thus also the electrochemical properties of the material are retained.

12:00pm - 12:15pm

Laser-based 3D-magnetic field sensor formation

Markus Müller, Mandy Gebhardt

3D-Micromac AG, Germany

A world with intelligent electronic devices in every machine and every pocket needs a wide range of sensor technologies. One rapidly growing technology is the sensing of magnetic fields, which can be used in numerous industrial applications. Very sensitive magnetic sensor chips can be realized by using GMR or TMR (Giant or Tunneling magnetoresistance) sensors in a Wheatstone bridge circuit built in a monolithic design.

This presentation gives an overview to selective laser annealing for 3D-magnetic field sensor formation, which provides several advantages over thermal annealing for magnetic sensor manufacturing. Its higher precision enables processing of smaller magnetic device structures, which in turn leads to more devices per wafer. In addition, its ability to set different reference magnetization directions on sensors across a single wafer reduces process steps and simplifies the manufacturing flow, enabling more cost-effective production of integrated monolithic sensor packages.

12:15pm - 12:30pm

Top-hat profile beam to weld polymeric microfluidics chips with ultra-short pulsed laser

Marc Décultot1, Jérôme Patars1, Anne Henrottin1, José Antonio Ramos-de-Campos1, Ivan Gusachenko2, Clément Jacquard2, Guillaume Labroille2, Gwenn Pallier2

1Lasea, Belgium; 2Cailabs, France

The microfluidics field, due to its various possibilities in the study of chemical and biological reactions with only few consumables, is expanding significantly. To follow this growing, we have developed a flexible solution, based on ultra-short pulsed laser technology, to engrave different microfluidic channels on a chip, and to seal them with a complete, hermetical, and resistant welding.

In order to improve the competitiveness of our solution for industrial production purpose, we have focused in particular our work on the improvement of the welding’s speed. Using the Canunda-Pulse solutions from Cailabs for manipulating high-power femtosecond lasers, we have made a complete study on laser welding parameters with a top-hat profile beam. Canunda-Pulse is a fully reflective passive optical module based on the Multi-Plane Light Conversion (MPLC) technology. Thanks to this beam shaper, we have deduced advantages of a top-hat profile beam, compared to a gaussian profile beam.

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 - 2:30pmMacro: Beam Oscillation
Location: Room 1
Session Chair: Prof. Thomas Graf, University of Stuttgart, Germany
Room 1 
1:30pm - 1:45pm

High speed videography of gap bridging with beam oscillation and wire feeding during the laser welding of stainless steel and aluminum alloys

Davide Maria Boldrin, Matteo Colopi, Simone D'Arcangelo, Leonardo Caprio, Ali Gökhan Demir, Barbara Previtali

Politecnico di Milano, Italy

Laser beam welding is known for its quality and speed. Given its susceptibility to gaps, the technology is applied in the industrial field with hard automation and dedicated fixtures rather than small-batch production. The latter cannot always guarantee the strict conditions on the fit-up of joints, especially with complex geometries. Gap-bridging techniques may be exploited to overcome these inaccuracies. The present work investigates the simultaneous use of low frequency circular beam oscillation and wire feeding as means to produce a continuous weld seam in the presence of constant air gaps. Lap joint welding of 2 mm-thick AISI301LN and butt joint welding of 3 mm-thick AW6005A-T6 alloy were conducted with gaps up to 1mm. High-speed imaging at 10kHz provided an insight in the dynamics of the oscillating weld pool and spatter formation. Optical inspection and metallographic analyses were used to verify the gap-bridging capability as well as the resulting seam quality.

1:45pm - 2:00pm

Influence of laser beam welding with overlaid high-frequency beam oscillation on weld seam quality and fatigue strength of aluminium wrought and die-cast joints

Benjamin Keßler, Dirk Dittrich, Robert Kühne, Markus Wagner, Axel Jahn

Fraunhofer Institute for Material and Beam Technology IWS, Dresden

Legal regulations with the aim of avoiding carbon dioxide emissions are drivers of innovation for lightweight automotive design.The economic production of such components is mainly achieved by using aluminium die-casts. A limiting factor for the use of aluminium die-castings is their weldability. The laser beam welding with overlaid high-frequency beam oscillation (LBW-HF) is a suitable solution to overcome this limitation.

In the proposed paper, weld specimens in form of aluminium mixed joints (wrought and die-cast alloys) were produced with the LBW-HF and with the static laser beam welding process (LBW). The weld seam quality is correlated with the tensile and fatigue strength properties. Furthermore, the results from the fatigue test are classified in the existing IIW regulations and their applicability with regard to laser-welded aluminium joints will be discussed. The results show an increased fatigue strength, especially for the LBW-HF process, compared to current used standards for design.

2:00pm - 2:15pm

Investigation of the influence of beam oscillation on the laser beam cutting process using high-speed X-ray imaging

Jannik Lind1,2, Jonas Wagner1, Niklas Weckenmann2, Weber Rudolf1, Thomas Graf1

1Institut für Strahlwerkzeuge (IFSW), University of Stuttgart, Germany; 2Precitec GmbH & Co. KG, Germany

Recently, it was shown that oscillating the laser beam during laser beam cutting can increase the maximum cutting feed rate compared to cutting with a static beam. In order to investigate this phenomenon, the geometry of the laser cutting front was observed by means of online high-speed X-ray imaging. Fusion cutting of 10 mm thick samples of stainless steel was recorded with a framerate of 1000 Hz. When the beam was oscillated in longitudinal direction, the maximum cutting feed rate could be increased by 25% compared to cutting with a static laser beam. In the talk, the influence of the oscillation parameters on the cutting speed, the cutting front geometry and the resulting cut quality will be discussed.

2:15pm - 2:30pm

CFD simulations for laser oscillation welding

Pareekshith Allu1, Frieder Semler2

1Flow Science Inc., United States of America; 2Flow Science Deutschland GmbH, Germany

Computational fluid dynamics (CFD) models have shown that laser keyhole welding at high speeds and powers can result in weld joints with reduced porosity. However, the process is limited by available laser powers (~6kW) and by insufficient penetration due to high welding velocities. To enable high speed welds with reduced porosity and optimal gap bridging, researchers have investigated laser oscillation welding. In this presentation, we look at some case studies where CFD models that simulate the laser-material interaction, melt pool dynamics and keyhole formation are developed to investigate laser oscillation welding in Zinc-coated steels. Additionally, these models helped identify zones of high Zinc vapor pressure that led to spatter and the data is compared to melt pool videos taken of the welding process. Such CFD models help develop welding schedules that limit the build of Zinc Vapor pressure in the melt pool and reduce spatter in laser oscillation welding.

1:30pm - 2:30pmAdditive Manufacturing: LIFT
Location: Room 2
Session Chair: Antoni Artinov, BAM Federal Institute for Materials Research and Testing, Germany
Room 2 
1:30pm - 1:45pm

Cavitation phenomena in BA-LIFT

Juan José Moreno Labella1,2, Miguel Morales Furió1,2, David Muñoz Martín1,3, Carlos Molpeceres Álvarez1,2

1Centro Láser, Universidad Politécnica de Madrid, Spain; 2Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, Spain; 3Escuela Técnica Superior de Ingeniería y Diseño Industrial, Universidad Politécnica de Madrid, Spain

Blister-Actuated Laser-Induced Forward Transfer (BA-LIFT) allows transferring high-resolution voxels or droplets of fluids with a wide range of viscosities. When compared to similar techniques, BA-LIFT stands out in its flexibility in design and the absence of a nozzle that may get clogged. The physics involved in the process is not easy to understand, so image acquisition systems and simulation are the main methods to gain insight into the dynamics of the process. The simulation of the transference process using a Phase-Field Finite-Element Model aids the task of understanding how the transferred material behaves. BA-LIFT long-time secondary effects, such as bulgy shapes and secondary jets, have been simulated including the effects that a mechanically-induced cavitation bubble would induce. An evaluation of its appearance causes has been carried out. Finally, the bubble has been photographed by modifying the setup to avoid optical distortion.

1:45pm - 2:00pm

Laser technologies for the production of microLEDs

Markus Müller, Uwe Wagner, Mandy Gebhardt

3D-Micromac AG, Germany

MicroLEDs have a tremendous potential for future displays. However, there are several technical challenges to overcome prior to widespread deployment of MicroLEDs. One key hurdle is developing a process to release the dies from the sapphire growth wafer. Another is a process to transfer these to the display substrate with micron level precision and reliability.
Laser processing offers several opportunities for MicroLED display production, such as Laser Lift-Off (LLO) to separate the finished MicroLEDs from the sapphire growth wafer and Laser Induced Forward Transfer (LIFT) to move the devices from a donor to the substrate.
In this presentation, laser-based system solutions for the different manufacturing steps for MicroLEDs, will be presented. Integrated process control and monitoring is used to assure stable and reliable operation to ensure high throughput and low yield losses.

2:00pm - 2:30pm

Invited Talk: Additive Manufacturing of Electronics by LIFT

Alberto Piqué

U.S. Naval Research Laboratory, United States of America

Laser-induced forward transfer (LIFT) techniques have generated significant interest for applications in Additive Manufacturing of Electronics (AME). LIFT enables printing of functional materials ranging from silver nano-inks to working devices such as bare-die semiconductor components over a wide range of surfaces in an additive fashion achieving high transfer throughputs. This technique is a non-mechanical, non-contact direct-write process capable of operating in additive and subtractive modes ideally suited for applications in 3D microscale fabrication and in printed electronics. LIFT techniques are well suited for IoT applications as exemplified by their use in prototyping of hybrid electronics and embedded components. This presentation will provide an overview of the current state-of-the-art through examples of structures and circuits made by LIFT and discuss their role in the development of next generation laser-based techniques for AME.

This work was funded by the Office of Naval Research (ONR) through the Naval Research Laboratory Basic Research Program.

1:30pm - 2:30pmMicro: Processing of Transparent Materials 1
Location: Room 3
Session Chair: Dr. Thomas Stichel, Bayerisches Laserzentrum GmbH (blz), Germany
Room 3 
1:30pm - 1:45pm

Micromachining of transparent biocompatible polymers used as vision implants with bursts of femtosecond laser pulses

Simas Butkus, Evaldas Kažukauskas, Vytautas Jukna, Domas Paipulas, Valdas Sirutkaitis

Laser Research Center, Vilnius University, Lithuania

Biocompatible plastics are used for many different purposes (catheters, artificial heart components, dentistry products, etc.). An important field biocompatible polymers is the production of vision implants known as intraocular lenses (IOLs) or custom-shape contact lenses, which are typically produced by means of milling, turning or lathe cutting and subsequent polishing. The multiple-step process is expensive and may take up days to produce the final part which is individually customized to meet the patient's needs.

In this work we propose a novel, all-laser-based method for the production of custom-shape lenses which may work as eye-implants. The shape of the lens from the plastic material (Contamac CONTAFLEX 26% UV-IOL) is produced by means of femtosecond ablation in a few minutes and afterwards it is polished by utilizing burst of femtosecond pulses in the GHz regime. In this way, transparent optical-quality lenses are produced in under 5 minutes of laser fabrication.

1:45pm - 2:00pm

Solvent evaporation and annealing of solution-processed organic materials by laser irradiation on flexible substrates

Frederik Kiel1, Cemal Esen1, Andreas Ostendorf1, Volker Wirth2

1Ruhr-Universität Bochum, Germany; 2Focuslight LIMO GmbH, Bookenburgweg 4-8, 44319 Dortmund, Germany

The market for flexible, printed and organic electronics is rapidly growing. The production is often based on wet-chemical processes and the residual solvent needs to be removed. Conventional methods for solvent evaporation or annealing of functional layers in roll-to-roll (R2R-) processing are circulating-air- or infrared-dryers. These methods require a relatively large drying section and entail a long exposure time at elevated temperatures for the flexible substrates. By utilizing a diode-laser as heating source the installation space and especially the exposure time at elevated temperatures could be minimized.

A LIMO line laser system (450 W, 980 nm) was used to investigate the substitution of conventional drying/ annealing methods on a lab scale (laser line FWHM: 12,22x0,06 mm²) for organic photovoltaic cells resulting in comparable power conversion efficiencies to conventional methods at processing speeds of 1m/min.

These results are expected to be transferred from the lab scale to a R2R-system.

2:00pm - 2:15pm

Processing and wetting behavior of microstructured polymer foils

Felix Bouchard1, Marcos Soldera2, Robert Baumann1, Andrés-Fabián Lasagni1,3

1Technische Universität Dresden, Institut für Fertigungstechnik, George-Baehr-Str. 3c, 01069 Dresden, Germany; 2PROBIEN-CONICET, Dto. de Electrotecnia, Universidad Nacional del Comahue, Buenos Aires 1400, Neuquén 8300, Argentina; 3Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstraße 28, 01277 Dresden, Germany

The demand for surface functionalized plastics is constantly rising. Therefore, industrial-scalable methods capable to provide surfaces with new functions are necessary. In this study, we demonstrate a strategy to apply hierarchical microstructures to transparent polyethlyene therepthalate (PET) foils by plate to plate hot embossing. To that end, a stainless steel stamp was patterned using two laser based processes, namely Direct Laser Writing (DLW) and Direct Laser Interference Patterning (DLIP). Several single scale and multi scale structures with feature sizes in the range 3 µm up to 50 µm and depths between 0.1 µm and 10 µm were processed on the metal master and transfered to the PET surface. The topography characterization by confocal microscopy and scanning electron microscopy revealed a satisfactory replication of the micostructures from the stamp to the polymer, even for the smallest features with lateral sizes of ~100 nm. The patterned surfaces showed an increased hydrophobic behavior characterized by static water contact angles up to 105°.

2:15pm - 2:30pm

Femtosecond laser-assisted mould fabrication for metal casting at the micro-scale

Enrico Casamenti1, Luciano Borasi2, Adeline Durand2, Samuel Rey1, Raphaël Charvet2, Cyril Dénéreaz2, Andreas Mortensen2, Yves Bellouard1

1Galatea Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland; 2Laboratory of Mechanical Metallurgy (LMM), École Polytechnique Fédérale de Lausanne (EPFL), Switzerland

Existing technologies for the production of metallic 3D micro-components are, in their current state, either too slow to be economically viable or produce porous and imperfect metal structures. Here we overcome those barriers by bringing metal casting to the realm of microfabrication. We present a process that enables the production of freeform, dense, 3D metal architectures at speeds well above alternative approaches for metal 3D printing at the same resolution. Using femtosecond laser micro-machining combined with chemical etching, arbitrarily shaped 3D-cavities are carved out of fused quartz substrates and subsequently pressure-infiltrated with high melting point metals, such as pure silver, copper and gold and their alloys. The resulting glass/metal combinations contain interconnected dense metal 3D structures that are shaped freely with micrometric resolution to enable new types of micro-devices and composite structures.

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 - 4:00pmMacro: Welding, Dissimilar Materials
Location: Room 1
Session Chair: Oliver Seffer, Laser Zentrum Hannover e.V., Germany
Room 1 
2:45pm - 3:00pm

Vapor plume behavior during a standalone laser pulse on the dissimilar aluminum/titanium interface: high-speed imaging with 810 nm band-pass filter

Manoj Raja Kumar, Iryna Tomashchuk, Jean-Marie Jouvard, Melanie Duband

Université de Bourgogne Franche-Comté, France

The understanding of plume behavior in dissimilar laser welding is little studied and can bring an insight to the concurrent vaporization process and keyhole dynamics. The present study is dedicated to the high-speed imaging and post-mortem characterization of a standalone Yb:YAG laser pulse on aluminum A5754/titanium interface with different offsets to the joint line. Plume morphology, dimensions, orientation and propagation velocities were characterized basing on the videos performed with a 810 nm band-pass filter. The main observed feature of the plume was its pronounced initial inclination towards aluminum side, accentuated by the beam offset on aluminum and reduced by the offset on titanium, followed by a progressive redressing resulting in a close-to-vertical jet. This behavior was attributed to the domination of the vapor jet from titanium side over that of aluminum side during the evolution of keyhole curvature. SEM observations of the melt were found in agreement with this statement.

3:00pm - 3:15pm

New strategies for joining of aluminum alloys to steel by means of laser

Daniel Wallerstein1, Antti Salminen2, Fernando Lusquiños1, Rafael Comesaña3, Jesús del Val1, Antonio Riveiro3, Aida Badaoui3, Juan Pou1

1CINTECX, University of Vigo, LaserON Research Group, Vigo, SPAIN; 2Department of Mechanical and Materials Engineering, University of Turku, Turku, FINLAND; 3Materials Engineering, Applied Mechanics and Construction Dpt., University of Vigo, EEI, Vigo, SPAIN

Joining steel and aluminum, is still a challenging task. This is due to significant differences in their fusion, expansion coefficients, thermal conductivity, and the practically zero solubility of Fe in Al. This low solubility leads to formation of intermetallic compounds (IMCs) on the interface between aluminum and steel.

IMCs are necessary to effectively join aluminum and steel, but the intermetallic layer can seriously deteriorate the mechanical properties of the joint.The growth of the IMC layer is the consequence of a diffusion process and, therefore, it is dependent on the welding thermal cycle. In this context, laser welding stands out relative to other welding processes by providing high energy densities and processing, with a moderate heat input.

This paper presents recent developments on the laser joining of aluminum alloys to steel. Succesfull examples of this type of dissimilar welding will be shown, comparing the mechanical performance of the final joint parts.

3:15pm - 3:30pm

Joining dissimliar materials: a new approach based on laser beam welding and melt displacement by electromagnetic forces

Jennifer Heßmann, Marcel Bachmann, Kai Hilgenberg

BAM, Germany

In order to reduce weight of vehicles, the interest in multi-material-design has been growing within the last few years. For vehicles the combination of steel and aluminium alloys offers the most promising compromise between weight, strength and formability. Thermal joining of these dissimilar materials is still a challenge to overcome. A possible approach is a new joining technology, whereby a combination of laser beam welding and contactless induced electromagnetic forces are used to displace the generated melt of one joining partner into a notch of the other. This paper presents the working principle and shows numerical analyses to improve the understanding of this joining process. The simulations help to calculate the thermal development of the joining partners, which is important for the formation of intermetallic phases. Furthermore, the calculation of the time required for a complete displacement is possible. The numerical results are validated by experimental results.

3:30pm - 3:45pm

Temperature measurement for heat conduction laser joining of metals to polymers

Mahdi Amne Elahi, Max Hennico, Peter Plapper

University of Luxembourg, Luxembourg

Laser joining of metals to polymers offers several advantages to produce hybrid assemblies of metals and polymers. One of the most important ones is the exceptional control over the heat input which defines the temperature at the interface of the materials. For the current study, the materials are joined in an overlap configuration with the heat conduction laser joining technique. To enlarge the joining area, beam trajectory was implemented with a continuous-wave fiber laser. The temperature was recorded simultaneously at different areas between the materials with K type thermocouples to identify the behavior of polymer at different temperatures. The results show that due to excessive heat input, polyamide degrades and leaves porosities near the interface of metal/polymer. The optimum condition considering mechanical properties of the welded samples and the absence of the porosities is achievable in a narrow process window between the melting range and the degradation of the polyamide.

3:45pm - 4:00pm

Metallurgy of dissimilar laser beam welded lap joints of supra-ductile and ultra-high strength steels

Martin Dahmen, Berkan Deniz, Dirk Petring

Fraunhofer Institute for Laser Technology, Steinbachstrasse 15, 52014 Aachen, Germany

Results of research on laser beam welding of a high manganese X30MnCrN16-14 (1.4678) to a press hardened X46Cr13 (1.4304), a dual phase steel (1.0944), and a press-hardened manganese boron steel (1.5528) in lap joint configuration will be reported. A pre-assessment of the local mechanical properties by micro hardness measurements revealed their uneven distribution over the weld zone. Based on metallographic inspection the underlying microstructures were revealed. By EDS analyses the local alloy constitutions were determined and assed by of COHMS diagrams. It was confirmed that in the combination with the high manganese steel the formation of ferritic phases, ferrite is largely suppressed to the favour of austenite and α’ and ε martensite. These findings were in part confirmed by nano indentation. The results allow an insight into the properties linked to melt transport, but indicate some further research.

2:45pm - 4:00pmAdditive Manufacturing: Directed Energy Deposition 4
Location: Room 2
Session Chair: Dr. Elena Lopez, AGENT-3D e.V., Germany
Room 2 
2:45pm - 3:00pm

Optical monitoring sensor system for laser-based directed energy deposition

Bohdan Vykhtar, Alexander Marek Richter

Fraunhofer Research Institution for Additive Manufacturing Technologies IAPT

To achieve homogeneous material properties and thus high-quality components, a constant melt pool geometry and temperature are essential during the laser-based directed energy deposition processes. Especially at high deposition rates, process instabilities can appear, which lead to deviations in melt pool properties consequently resulting in the discrepancy in the target/actual comparison and, in the worst case, in the disposal of the component. To monitor the continuity of the melt pool properties, this paper presents an optical monitoring sensor system, which is capable of monitoring the process by guiding, filtering, and analyzing the optical signals of the melt pool. The presented sensor system is mounted on-axis to accomplish image acquisition and monitor the melt pool emissions but is also off-axis integrable in hybrid and wire-arc-based (AM)-processes. The system is demonstrated for melt pool monitoring while processing stainless steel and an outlook is given on using that information to control the whole process.

3:00pm - 3:15pm

A measuring system based on chromatic confocal displacement sensor integrated with laser head for monitoring of laser metal deposition process

Piotr Koruba, Adrian Zakrzewski, Piotr Jurewicz, Michał Ćwikła, Jacek Reiner

Wroclaw University of Science and Technology, Poland

The measurement of geometrical properties of a sample during laser material processing is still an open research issue. Thus, the knowledge about the laser focus in relation to sample before, during and after the process is considered as one of the most crucial parameters. In this study, we indicate that the chromatic confocal displacement sensor integrated with laser head can serve as an alternative for current solutions used in monitoring of laser metal deposition process. Therefore, the design procedures of measuring system is described, consisting in numerical modelling, selection of system components. Moreover, in order to determine the functionality parameters of the system it was experimentally characterized in two regimes i.e. off-line and on-line (with and without presence of laser beam, respectively). Additionally, the various methods for spectral data processing were presented. Finally, the preliminary measurement results obtained with the measuring system during laser metal deposition were presented and discussed.

3:15pm - 3:30pm

Rotary straightening of fine wire for LMD-W applications

Sirko Pamin, Maximilian Grafe, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

In wire-based high-precision laser applications as micro welding or micro laser metal deposition the straightness of the wire used plays an essential role. Small process windows require constant input conditions and thus straight wire without deformations. Uncoiled commercial wire exhibits a spatial, often helix-like curvature as a result of previous recoil processes on comparatively small reels. With the rotary straightener developed in this work, stainless steel wires with diameters of 75 µm and 100 µm, respectively, were straightened from average curvature levels of 22.56 1/m down to 0.61 1/m by alternating bending. This cold forming process causes crystallographic irregularities (dislocations) and residual stresses, which additionally lead to a rise in hardness and yield strength of the wire. For subsequent laser processes the changed material properties are advantageous, as they increase process robustness and enable a longer wire stick-out.

3:30pm - 3:45pm

Height variation in scanned hot-wire laser surfacing processes

Alexander Barroi, Kai Biester, Laura Budde, Marius Lammers, Jörg Hermsdorf, Ludger Overmeyer

Laser Zentrum Hannover e.V., Germany

The use of hot wire in laser cladding can raise the energy efficiency and the deposition rate of the process drastically. This study shows that when using hot wire, the process faces stronger restrictions to one of the process parameters, the wire nozzle height. A change of three millimeters in wire nozzle height can double the dilution. This is because of the impact of stick out length on the wire heating. But not only the heating has an effect when changing the height, it also changes the wire positioning, a parameter which is sensible for the process stability.

3:45pm - 4:00pm

Automatic changing of weld deposit for additive manufacturing of hybrid metal-glass components using direct laser deposition

Marius Lammers1,2, Kai Biester1, Nick Schwarz1,2, Jörg Hermsdorf1, Stefan Kaierle1, Henning Ahlers2

1Laser Zentrum Hannover e.V., Germany; 2Hochschule Hannover – University of Applied Sciences and Arts, Germany

Direct Laser Deposition is a manufacturing process, which enables Additive Manufacturing of nearly any fusible material. For example metal or glass materials can be processed.

For generating hybrid components out of metal and fused silica, systems technology with coaxial beam guidance using different laser beam sources can be used enabling direct manufacturing of optical, structural and thermal elements. To suit both processes, a wide velocity range regarding the weld material feed from 0.1 to 5 m/min is required.

In this paper a prototype machine for material feeding and changing is presented. The system is designed for metal wire and glass fibre feeding. In order to determine process-critical parameters, preliminary tests are carried out to determine the requirements for the system. The paper also shows how the prototype system performs in terms of changing and conveying the wires as well as fibers with a focus on wear and changing cycles.

2:45pm - 4:00pmMicro: Processing of Transparent Materials 2
Location: Room 3
Session Chair: Dr. Kristian Cvecek, Institute of Photonic Technologies (LPT), Germany
Room 3 
2:45pm - 3:00pm

Deep engraving of fused silica glass using bursts of femtosecond pulses with intra-burst frequencies in the range of 25 - 100 GHz

Simas Butkus1,2, Martynas Barkauskas1,2, Aurimas Augus1, Martynas Kojelis1, Jonas Pocius1, Linas Giniūnas1

1Light Conversion, Lithuania; 2Laser Research Center, Vilnius University, Lithuania

Due to the high precision offered by ultrashort pulse micromachining, femtosecond laser systems are applied in both industrial and scientific fields. To accompany the needs of the industry, a trend towards high average power (>100 W) femtosecond laser systems for micromachining has become apparent. However, upscaling the micromachining throughput is not straightforward and typically results in a decrease in the micromachining quality. To this end, new ideas are sought to increase the efficiency of an ablation-based process.

In this work we present data on deep engraving of fused silica glass using burst of femtosecond pulses with a custom-built laser capable of tuning the intra-burst temporal gap producing a variable effective repetition rate of 25 – 100 GHz. By adjusting the average power, number of sub-pulses within the burst and the intra-burst gap it was found that the ablation efficiency can be increased by several-fold as compared to the convention single-pulse regime.

3:00pm - 3:15pm

Fully reflective Bessel beam generation with constant energy distribution over the propagation axis for complex glass cutting

Siddharth Sivankutty, Antonin Billaud, Gwenn Pallier, Pu Jian, Olivier Pinel, Guillaume Labroille

Cailabs, France

Glass cutting with femtosecond lasers is spreading led by the touch panel displays development. Bessel beams are very efficient and precise way to process glass thanks to their extended depth of focus 100 times longer than a standard Gaussian beam and their central beam which can be smaller than the diffraction limit.

High quality glass cutting with a reflective axicon has already been demonstrated with no oscillations leading to cleaner cuts and faster processes. The beam is able to propagate through a galvo-scanner and a F-theta lens. The reflective design is compatible with extreme high peak and average power.

Here we describe the generation of a complex Bessel beam profile flatter over the propagation axis based on a reflective design. The tail of this profile is five times sharper compared to standard Bessel beams paving the way to complex glass cutting such as multi-layer glasses.

3:15pm - 3:30pm

Optical coherence tomography for 3D weld seam localization in absorber-free laser transmission welding

Frederik Maiwald1, Clemens Roider2, Michael Schmidt2,3, Stefan Hierl1

1Ostbayerische Technische Hochschule Regensburg, Labor Lasermaterialbearbeitung, Technologie Campus Parsberg-Lupburg, Am Campus 1, 92331 Parsberg, Germany; 2Institute of Photonic Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Konrad-Zuse-Straße 3/5, 91052 Erlangen, Germany; 3Erlangen Graduate School in Advanced Optical Technologies (SAOT), Paul-Gordan-Str. 6, 91052 Erlangen, Germany

Thulium fibre lasers emit in the intrinsic absorption spectrum of polymers and enable welding of transparent parts without absorbent additives. Focusing with high NA provides large intensity gradients inside the workpiece, enabling selective fusing of the joining zone without affecting the surface. Therefore, absorber-free laser transmission welding is well suited to fulfil the high demands on quality and reliability in manufacturing of optical and medical devices. However, monitoring the welding process is required, since seam size and position are crucial for quality.

The aim of this work is the volumetric acquisition of the weld seam’s location and size using optical coherence tomography. Due to the change of the optical properties during melting, the seam can be distinguished from the base material. The results coincide with microscopic images of microtome sections and demonstrate that weld seam localization in polyamide 6 is possible with an accuracy better than a tenth of a millimetre.

3:30pm - 3:45pm

Laser-manufactured glass microfluidic devices with embedded sensors

Krystian L. Wlodarczyk1,2, William N. MacPherson2, Duncan P. Hand2, M. Mercedes Maroto-Valer1

1Research Centre for Carbon Solutions, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, UK; 2Applied Optics and Photonics group, School of Engineering and Physical Sciences, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, UK

Recently, we have developed a laser process that enables the rapid fabrication of microfluidic devices using widely-available borosilicate glass slides. In contrast to conventional manufacturing techniques, there is no requirement for projection masks and hazardous glass etchants, such as hydrofluoric acid. Instead, a single item of equipment, i.e. an ultrashort pulsed picosecond laser (Trumpf TruMicro 5x50), is used to: (a) write microfluidic patterns directly onto the glass surface by ablating the material and (b) permanently enclose the microfluidic structure from the top by welding this glass substrate to another glass slide that typically contains inlet/outlet ports. In this work, we demonstrate that this process also allows us to manufacture customised glass microfluidic devices with embedded sensors, which enable local, real-time monitoring of various parameters, such as pressure and pH, inside the microfluidic patterns.

3:45pm - 4:00pm

Ultrashort pulse laser cutting of colorless polyimide and hard coat film stacks for flexible OLED displays

Jim Bovatsek, Terence Hollister

MKS Spectra-Physics, United States of America

New mobile devices include flexible and foldable OLED displays which require new protective cover materials. Options for this include ultrathin glass (UTG) as well as a new type of colorless polyimide (CPI), which is transparent at visible wavelengths. The CPI is combined with a scratch resistant hard coat (HC) layer and a final PET (polyethylene terephthalate) protective film. Here we present results for cutting thick CPI/HC/PET layered stacks using high power UV ultrashort pulse lasers. Ablation thresholds were found to vary by almost a factor of ten, and a layer-optimized cutting approach was used. The optimized cutting process is of high quality and throughput, with heat-affect zone (HAZ) of <10 µm and cutting speed of >400 mm/s. These results are comparable to that for individual sheets of polymers used in OLED display manufacturing.

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.

4:00pm - 4:10pmClosing Session
Location: Room 1
Session Chair: Prof. Michael Rethmeier, Bundesanstalt für Materialforschung und -prüfung (BAM), Germany
Room 1 

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