2:45pm - 3:00pm
Improvement of hardness and wear-resistance of direct laser interference patterned bearing steel surface using laser surface heating approach
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
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
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
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
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.