TY - JOUR A1 - Grad, Marius A1 - Nadammal, Naresh A1 - Schultheiss, Ulrich A1 - Lulla, Philipp A1 - Noster, Ulf T1 - An Integrative Experimental Approach to Design Optimization and Removal Strategies of Supporting Structures Used during L-PBF of SS316L Aortic Stents JF - Applied Sciences N2 - One of the fundamental challenges in L-PBF of filigree geometries, such as aortic stents used in biomedical applications, is the requirement for a robust yet easily removable support structure that allows each component to be successfully fabricated without distortion. To solve this challenge, an integrative experimental approach was attempted in the present study by identifying an optimal support structure design and an optimized support removal strategy for this design. The specimens were manufactured using four different support structure designs based on the geometry exposed to the laser beam during the L-PBF. Support removal procedures included sand blasting (SB), glass bead blasting (GB), and electrochemical polishing (ECP). The two best-performing designs (line and cross) were chosen due to shorter lead times and lower material consumption. As an additional factor that indicates a stable design, the breaking load requirement to remove the support structures was determined. A modified line support with a 145° included angle was shown to be the best support structure design in terms of breaking load, material consumption, and manufacturing time. All three procedures were used to ensure residue-free support removal for this modified line support design, with ECP proving to be the most effective. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-25612 N1 - Corresponding author: Marius Grad VL - 11 IS - 19 SP - 1 EP - 22 PB - MPDL ER - TY - JOUR A1 - Wiesent, Lisa A1 - Schultheiß, Ulrich A1 - Lulla, Philipp A1 - Nonn, Aida A1 - Noster, Ulf T1 - Mechanical properties of small structures built by selective laser melting 316 L stainless steel – a phenomenological approach to improve component design JF - Materials Science & Engineering Technology JF - Materialwissenschaft und Werkstofftechnik N2 - Experimental investigations are conducted to quantify the influence of specimen thickness and orientation on the mechanical properties of selective laser melted stainless steel 316 L. The results indicate that the mechanical strength and ductility increase with increasing specimen thickness until a saturation value is reached from a specimen thickness of about 2 mm. Specimen orientation dependency is pronounced for thin specimens (<1.5 mm), whereas only small deviations in strength are observed for thicker specimens with orientations of 30°, 45° and 90° to build direction. The mechanical properties of the specimen orientation of 0° to build direction shows great deviation to the other orientations and the smallest overall strength. A reliable design of selective laser melted components should account for specimen thickness and orientation, e. g. by a correction factor. Furthermore, it is recommended to avoid loads vertical (90°) and parallel (0°) to build direction to guarantee higher ductility and strength. T2 - Mechanische Eigenschaften von kleinen Strukturen aus selektiv lasergeschmolzenem 316 L Edelstahl – ein phänomenologischer Ansatz zur Verbesserung des Bauteildesigns Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-14718 N1 - Corresponding author: Lisa Wiesent VL - 51 IS - 12 SP - 1615 EP - 1629 PB - Wiley ER - TY - JOUR A1 - Grad, Marius A1 - Zentgraf, Jan A1 - Schultheiss, Ulrich A1 - Esper, Lukas A1 - Diemar, Andreas A1 - Noster, Ulf A1 - Spiess, Lothar T1 - Effect of Carbon Content on the Phase Composition, Microstructure and Mechanical Properties of the TiC Layer Formed in Hot-Pressed Titanium-Steel Composites JF - Metals N2 - During the hot pressing of pure titanium and different carbon steels in a temperature range of ϑ = 950–1050 °C, a compound layer up to dL≈10 μm thick is formed at the titanium–steel interface. With a higher carbon content of the used steel, the layer thickness increases. The carbon concentration within the layer is in the range of stoichiometry for TiC. Apart from TiC, no other phases can be detected by X-ray diffraction (XRD) measurements inside the formed layer. The calculation of the activation energy for the TiC layer formation is Q = 126.5–136.7 kJ mol−1 and is independent of the carbon content of the steel. The resulting microstructure has a grain size gradient, wherein the mechanical properties, such as hardness and Young‘s modulus, are almost constant. Statistical analysis using Response Surface Methodology (RSM) indicates that the carbon content of the steel has the most significant influence on layer thickness, followed by annealing temperature and annealing time. By selecting the appropriate carbon steel and the subsequent removal of the steel, it is possible to produce targeted TiC layers on titanium substrates, which holds enormous potential for this material in wear-intensive applications. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-74617 SN - 2075-4701 N1 - Cooresponding author der OTH Regensburg: Marius Grad VL - 14 IS - 9 PB - MDPI AG ER - TY - JOUR A1 - Tezel, Tugce A1 - Schultheiss, Ulrich A1 - Hornberger, Helga A1 - Kovan, Volkan T1 - Operational wear behaviour of 3D-printed lightweight metal gears: EDS and oil analysis comparison JF - Materials Testing N2 - Additive manufacturing (AM) has come to the fore in recent years among manufacturing techniques. This technique, which has different advantages than traditional ones such as casting, forging and machining, is expected to be widely used in producing machine parts like gears in the coming years. Therefore, experimental data on AM parameters for lightweight metal gears are important for industrial production. In this study, a wear test was applied to AlSi10Mg and Ti6Al4V gears under operational conditions, and the wear behaviour of conventionally and additively manufactured gears was compared. The amount of abrasion elements was determined by analysing the oil in the gearbox. In addition, gear surfaces were analysed using scanning electron microscopy and an energy-dispersive spectrometer before and after wear. Thus, the wear behaviour of gears produced by conventional and AM under service conditions was demonstrated comparatively. KW - additive manufacturing KW - titanium KW - aluminium KW - gear KW - wear Y1 - 2024 U6 - https://doi.org/10.1515/mt-2023-0222 SN - 0025-5300 VL - 66 IS - 6 SP - 830 EP - 834 PB - de Gruyter ER - TY - JOUR A1 - Kloiber, Jessica A1 - Anetsberger, Viktoria A1 - Schultheiß, Ulrich A1 - Hornberger, Helga T1 - High quality surfaces of magnesium alloy AZ31 by adjusting appropriate electropolishing parameters JF - Electrochimica Acta Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-79298 N1 - Corresponding author der OTH Regensburg: Jessica Kloiber VL - 513 PB - Elsevier ER - TY - JOUR A1 - Kloiber, Jessica A1 - Schultheiß, Ulrich A1 - Hornberger, Helga T1 - Impact of heat treatment on the surface quality of electropolished WE43 alloy JF - Materials Letters N2 - In this study, the Mg alloy WE43 was solution annealed and precipitation hardened prior to electropolishing to evaluate the effects of different microstructures on the electropolishing result. While coarsely distributed precipitates led to surfaces showing wavy structures and dents after electropolishing, a uniform microstructure resulted in an even finish of the surface. The homogenization and refinement of the microstructure by heat treatment is a method to ensure improved electropolished surfaces of Mg materials Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-83512 SN - 0167-577X N1 - Corresponding author der OTH Regensburg: Jessica Kloiber VL - 397 PB - Elsevier BV ER - TY - JOUR A1 - Schultheiß, Ulrich A1 - Hornberger, Helga T1 - Comparison of etchants for corrosion-resistant stainless steels in medical engineering JF - Practical Metallography N2 - Corrosion-resistant stainless steels are widely used in medical engineering. Today, additive manufacturing techniques are also used for this purpose, in particular for implant steels. Additively processed materials sometimes react differently to etching than conventionally processed ones. The use of etchants for contrasting the microstructure must therefore be adapted. Chemical etching using V2A etchant, Murakami, and anhydrous Kalling solutions, as well as electrochemical etching using nitric acid, sodium hydroxide, and oxalic acid were performed. Etched samples made of conventionally processed X2CrNi-Mo17-12-2 were compared to samples manufactured using selective laser melting and sintering, and the optimal contrast was developed in each case. It can be shown that the different etchants reveal different microstructural constituents and that etchants must therefore be selected as a function of the application. N2 - Korrosionsbeständige Edelstähle werden vielfältig in der Medizintechnik eingesetzt. Dabei werden insbesondere bei Implantat-Stählen heute auch additive Fertigungstechniken angewandt. Additiv verarbeitete Materialien reagieren teilweise anders beim Ätzen als konventionell verarbeitete, weshalb der Einsatz von Ätzmitteln zur Gefüge-Kontrastierung adaptiert werden muss. Es wurde sowohl chemisch mit V2A-Beize, Murakami- und wasserfreier Kalling-Lösung geätzt, als auch elektrochemisch mit Salpetersäure, Natronlauge und Oxalsäure. Geätzte Proben aus konventionell verarbeitetem X2CrNiMo17-12-2 wurden mit Proben verglichen, die mittels selektivem Laserschmelzen und -sintern hergestellt wurden, und die jeweils optimale Kontrastierung entwickelt. Es kann gezeigt werden, dass die unterschiedlichen Ätzmittel verschiedene Gefügebestandteile hervorheben und somit je nach Anwendungsfall das jeweilige Ätzmittel ausgewählt werden muss. Y1 - 2024 U6 - https://doi.org/10.1515/pm-2024-0094 VL - 62 IS - 1 SP - 19 EP - 30 PB - de Gruyter ER - TY - INPR A1 - Kloiber, Jessica A1 - Anetsberger, Viktoria A1 - Schultheiss, Ulrich A1 - Hornberger, Helga T1 - Electropolishing of Magnesium Alloy Az31 with Varying Electrolyte Concentrations and Applied Potentials N2 - Magnesium alloy AZ31 is a light material with a good mechanical stability and is used in various engineering applications. Although its tendency to localized corrosion is a limiting factor in its use. Electropolishing is a widely used process for improving the surface roughness and corrosion behavior of metals. However, there is a lack of knowledge about the electropolishing of magnesium and its alloys. In this study, an optimal electropolishing process for AZ31 was developed to improve the surface properties by varying the electrolyte concentration and the applied potential. The electrolyte composition was a mixture of phosphoric acid, ethanol and deionized water. The applied potentials were selected based on measured current density potential curves. Thereby, electropolishing was performed up to an electric charge of 18 As. The experimental results indicate that the electropolishing process should be carried out at a low current density to avoid bubble evolution and surface defects. Therefore, the concentration of the electropolishing electrolyte should have an appropriate low conductivity, and the applied potential should be in the transient or passive region of the polarization curve recorded prior to electropolishing. It could be shown that an optimized electropolishing process improved the surface of AZ31 by providing a bright and mirror-like surface and a lower roughness compared to a mechanically ground surface. KW - magnesium alloy KW - AZ31 KW - electropolishing KW - electrolyte KW - surface characterization KW - polarization curve Y1 - 2024 U6 - https://doi.org/10.2139/ssrn.4991311 PB - SSRN ER - TY - JOUR A1 - Tezel, Tugce A1 - Schultheiss, Ulrich A1 - Hornberger, Helga A1 - Kovan, Volkan T1 - Operational wear behaviour of 3D-printed lightweight metal gears: EDS and oil analysis comparison JF - Materials Testing N2 - Additive manufacturing (AM) has come to the fore in recent years among manufacturing techniques. This technique, which has different advantages than traditional ones such as casting, forging and machining, is expected to be widely used in producing machine parts like gears in the coming years. Therefore, experimental data on AM parameters for lightweight metal gears are important for industrial production. In this study, a wear test was applied to AlSi10Mg and Ti6Al4V gears under operational conditions, and the wear behaviour of conventionally and additively manufactured gears was compared. The amount of abrasion elements was determined by analysing the oil in the gearbox. In addition, gear surfaces were analysed using scanning electron microscopy and an energy-dispersive spectrometer before and after wear. Thus, the wear behaviour of gears produced by conventional and AM under service conditions was demonstrated comparatively. KW - gear KW - wear KW - additive manufacturing KW - titanium KW - aluminium Y1 - 2024 U6 - https://doi.org/10.1515/mt-2023-0222 SN - 2195-8572 VL - 66 IS - 6 SP - 830 EP - 834 PB - de Gruyter ER - TY - JOUR A1 - Wiesent, Lisa A1 - Schultheiss, Ulrich A1 - Schmid, Christof A1 - Schratzenstaller, Thomas A1 - Nonn, Aida T1 - Experimentally validated simulation of coronary stents considering different dogboning ratios and asymmetric stent positioning JF - PlOS One N2 - In-stent restenosis remains a major problem of arteriosclerosis treatment by stenting. Expansion-optimized stents could reduce this problem. With numerical simulations, stent designs/ expansion behaviours can be effectively analyzed. For reasons of efficiency, simplified models of balloon-expandable stents are often used, but their accuracy must be challenged due to insufficient experimental validation. In this work, a realistic stent life-cycle simulation has been performed including balloon folding, stent crimping and free expansion of the balloon-stent-system. The successful simulation and validation of two stent designs with homogenous and heterogeneous stent stiffness and an asymmetrically positioned stent on the balloon catheter confirm the universal applicability of the simulation approach. Dogboning ratio, as well as the final dimensions of the folded balloon, the crimped and expanded stent, correspond well to the experimental dimensions with only slight deviations. In contrast to the detailed stent life-cycle simulation, a displacement-controlled simulation can not predict the transient stent expansion, but is suitable to reproduce the final expanded stent shape and the associated stress states. The detailed stent life-cycle simulation is thus essential for stent expansion analysis/optimization, whereas for reasons of computational efficiency, the displacement-controlled approach can be considered in the context of pure stress analysis. KW - Catheters KW - Coronary stenting KW - Deformation KW - Stent implantation KW - Stiffness KW - Stent KW - Ballondilatation KW - Numerische Strömungssimulation Y1 - 2019 U6 - https://doi.org/10.1371/journal.pone.0224026 VL - 14 IS - 10 SP - 1 EP - 25 PB - PLOS ER - TY - GEN A1 - Wiesent, Lisa A1 - Hupke, Constantin A1 - Balk, Christian A1 - Schultheiss, Ulrich A1 - Schratzenstaller, Thomas T1 - Optimization of the cardiovascular stent design towards improved expansion behaviour and radial stiffness properties T2 - Biomedizinische Technik N2 - - Development of a FEA Tool for a realistic stent simulation - investigation on minor modification on the stent design on the expansion behaviour - analysis of three stent designs: classical stent design with pronounced dogbone effect, two modified stent design (non-dogbone-design) KW - Kardiovaskuläres System KW - Stent Y1 - 2018 U6 - https://doi.org/10.1515/bmt-2018-6031 VL - 63 IS - s1 ER - TY - JOUR A1 - Zentgraf, Jan A1 - Nützel, Florian A1 - Mühlbauer, Nico A1 - Schultheiss, Ulrich A1 - Grad, Marius A1 - Schratzenstaller, Thomas T1 - Surface Treatment of Additively Manufactured Polyetheretherketone (PEEK) by Centrifugal Disc Finishing Process: Identification of the Key Parameters JF - Polymers N2 - Polyetheretherketone is a promising material for implants due to its good mechanical properties and excellent biocompatibility. Its accessibility to a wide range of applications is facilitated by the ability to process it with an easy-to-use manufacturing process such as fused filament fabrication. The elimination of disadvantages associated with the manufacturing process, such as a poor surface quality, is a main challenge to deal with. As part of the mass finishing process, centrifugal disc finishing has demonstrated good results in surface optimization, making it a promising candidate for the post-processing of additively manufactured parts. The objective of this study is to identify the key parameters of the centrifugal disc finishing process on the waviness of additively manufactured PEEK specimens, which has not been investigated previously. The waviness of the specimen was investigated by means of confocal laser scanning microscopy (CLSM), while weight loss was additionally tracked. Six parameters were investigated: type, amount and speed of media, use of compound, amount of water and time. Type of media, time and speed were found to significantly influence waviness reduction and weight loss. Surface electron microscopy images demonstrated the additional effects of deburring and corner rounding. Results on previous studies with specimens made of metal showed similar results. Further investigation is required to optimize waviness reduction and polish parts in a second post-processing step. KW - PEEK KW - fused deposition modeling KW - fused filament fabrication KW - centrifugal disc finishing KW - mass finishing KW - 3D printing KW - post-processing of 3D printed parts KW - surface treatment KW - high-performance polymers KW - additive manufacturing Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-73959 SN - 2073-4360 N1 - Corresponding author der OTH Regensburg: Jan Zentgraf VL - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wiesent, Lisa A1 - Schultheiß, Ulrich A1 - Lulla, Philipp A1 - Noster, Ulf A1 - Schratzenstaller, Thomas A1 - Schmid, Christof A1 - Nonn, Aida A1 - Spear, Ashley T1 - Computational analysis of the effects of geometric irregularities and post-processing steps on the mechanical behavior of additively manufactured 316L stainless steel stents JF - PLoS ONE N2 - Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or the heat treated condition (5.87 ± 0.49 N) showed increased radial forces when compressed between two plates. After electropolishing, the heat treated stents exhibited radial forces (2.38 ± 0.23 N) comparable to conventional metallic stents. The laser powder bed fused stents were further affected by the size effect, resulting in a reduced yield strength by 41% in the as-built and by 59% in the heat treated condition compared to the bulk material obtained from tensile tests. The presented numerical approach was successful in predicting the macroscopic mechanical response of the stents under compression. During deformation, increased stiffness and local stress concentration were observed within the laser powder bed fused stents. Subsequent numerical expansion analysis of the derived stent models within a previously verified numerical model of stent expansion showed that electropolished and heat treated laser powder bed fused stents can exhibit comparable expansion behavior to conventional stents. The findings from this work motivate future experimental/numerical studies to quantify threshold values of critical geometric irregularities, which could be used to establish design guidelines for laser powder bed fused stents/lattice structures. KW - Heat treatment KW - Lasers KW - Surface treatments KW - Specimen preparation and treatment KW - Material properties KW - Stiffness KW - Deformation KW - Powders KW - Koronarendoprothese KW - Rapid prototyping KW - Numerische Methode Y1 - 2020 U6 - https://doi.org/10.1371/journal.pone.0244463 N1 - Corresponding author: Lisa Wiesent VL - 15 IS - 12 SP - 1 EP - 30 PB - PLOS ER - TY - JOUR A1 - Kloiber, Jessica A1 - Schultheiß, Ulrich A1 - Sotelo, Lamborghini A1 - Sarau, George A1 - Christiansen, Silke H. A1 - Gavras, Sarkis A1 - Hort, Norbert A1 - Hornberger, Helga T1 - Corrosion behaviour of electropolished magnesium materials JF - Materials Today Communications N2 - Although magnesium and its alloys are promising candidates as biodegradable implant materials, the tendency for localized corrosion mechanism in physiological environment limit their biomedical application. Electropolishing is an attractive strategy for improving the corrosion behaviour of metals, but it is still largely unexplored in magnesium materials. In this study, the characterization of electropolished surfaces of AM50 and pure magnesium was performed, focussing on their in vitro degradation behaviour in cell medium. Corrosion rates were evaluated using potentiodynamic polarisation. The surface morphology before and after the onset of corrosion was investigated by scanning electron microscopy and confocal laser scanning microscopy. The presented electropolishing process led to improved surface performances, observable by significantly lower corrosion rates (0.08 mm·year-1 in Dulbecco's modified Eagle's medium), lower arithmetical mean height (0.05 µm), lower water contact angle (25-35°) and lower micro hardness (35-50 HV 0.1) compared to mechanically and chemically treated surfaces. MgO/Mg(OH)2 could be detected on electropolished surfaces. The localized corrosion mode could be reduced, but not entirely prevented. Electropolishing shows great potential as post-treatment of magnesium-based components, but detailed tests of the long-term corrosion behaviour are an important area of future research. KW - biomedical application KW - corrosion behaviour KW - electropolishing KW - magnesium alloy KW - pure magnesium KW - surface characterization Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-68254 N1 - Corresponding author: Helga Hornberger PB - Elsevier ET - Journal Pre-proof ER - TY - JOUR A1 - Bartsch, Alexander A1 - Burger, Moritz A1 - Grad, Marius A1 - Esper, Lukas A1 - Schultheiß, Ulrich A1 - Noster, Ulf A1 - Schratzenstaller, Thomas T1 - Enhancement of laser cut edge quality of ultra-thin titanium grade 2 sheets by applying an in-process approach using modulated Yb:YAG continuous wave fiber laser JF - Discover Mechanical Engineering N2 - Titanium is used in many areas due to its excellent mechanical, biological and corrosion-resistant properties. Implants often have thin and filigree structures, providing an ideal application for fine cutting with laser. In the literature, the main focus is primarily on investigating and optimizing the parameters for titanium sheets with thicknesses greater than 1 mm. Hence, in this study, the basic manufacturing parameters of laser power, cutting speed and laser pulse of a 200 W modulated fiber laser are investigated for 0.15 mm thick grade 2 titanium sheets. A reproducible, continuous cut could be achieved using 90 W laser-power and 2 mm/s cutting-speed. Pulse pause variations between 85 and 335 μs in 50 μs steps and a fixed pulse width of 50 μs show that a minimum kerf width of 23.4 μm, as well as a minimum cut edge roughness Rz of 3.59 μm, is achieved at the lowest pulse pause duration. An increase in roughness towards the laser exit side, independent of the laser pulse pause duration, was found and discussed. The results provide initial process parameters for cutting thin titanium sheets and thus provide the basis for further investigations, such as the influence of cutting gas pressure and composition on the cut edge. KW - Laser cutting KW - Titanium sheet KW - Kerf Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-65647 N1 - Corresponding author: Alexander Bartsch IS - 10 PB - Springer ER - TY - INPR A1 - Grad, Marius A1 - Haag, Lydia A1 - Hahn, Konstantin A1 - Schultheiß, Ulrich A1 - Esper, Lukas A1 - Noster, Ulf T1 - Influence of carbon content on the formation of TiC at diffusion bonded titanium-steel interface N2 - Hot pressing of pure Ti and various carbon steels in a temperature range of 950 – 1050 °C creates an up to 9 μm thick compound layer of TiC at the Ti/ steel interface. The calculation of the activation energy for layer formation is 126.5 - 136.7 kJ/mol, independent of the steels carbon content. As the carbon content of the steel increases, the layer thickness also increases, which provides enormous potential for the surface modification of Ti/ Ti-alloys. Y1 - 2023 U6 - https://doi.org/10.2139/ssrn.4261928 PB - Elsevier ER - TY - INPR A1 - Burger, Moritz A1 - Bartsch, Alexander A1 - Grad, Marius A1 - Esper, Lukas A1 - Schultheiß, Ulrich A1 - Noster, Ulf A1 - Schratzenstaller, Thomas T1 - Enhancement of laser cut edge quality of ultra-thin titanium grade 2 sheets by applying in-process approach using modulated Yb:YAG continuous wave fibre laser N2 - Titanium is used in many areas due to its excellent mechanical, biological and corrosion-resistant properties. Implants often have thin and filigree structures, providing an ideal application for laser fine cutting. In literature, the main focus is primarily on investigating and optimizing the parameters for titanium sheet thicknesses greater than 1 mm. Hence, in this study, the basic manufacturing parameters of laser power, cutting speed and laser pulsing of a 200 W modulated fibre laser are investigated for 0.15 mm thick titanium grade 2 sheets. A reproducible, continuous cut could be achieved using 90 W laserpower and 2 cutting-speed. Pulse pause variations between 85–335 μs in 50 μs steps and fixed pulse duration of 50 μs show that a minimum kerf width of 23.4 μm, as well as a minimum cut edge roughness Rz of 3.59 μm, is achieved at the lowest pulse pause. An increase in roughness towards the laser exit side, independent of the laser pulse pause, was found and discussed. The results provide initial process parameters for cutting thin titanium sheets and thus provide the basis for further investigations, such as the influence of cutting gas pressure and composition on the cut edge. Y1 - 2023 U6 - https://doi.org/10.21203/rs.3.rs-2520041/v1 N1 - Erschienen in der Zeitschrift: Discover Mechanical Engineering, https://opus4.kobv.de/opus4-oth-regensburg/frontdoor/index/index/docId/6564 ER - TY - GEN A1 - Esper, Lukas A1 - Noster, Ulf A1 - Schultheiss, Ulrich A1 - Bund, Andreas T1 - Quasi-in-Situ Analysis of Electropolished Additively Manufactured Stainless Steel Surfaces T2 - ECS Meeting Abstracts, F01: Advances in Industrial Electrochemistry and Electrochemical Engineering N2 - Progress in additive manufacturing is leading to the emergence of new areas of application. Laser Powder Bed Fusion (L-PBF) is increasingly used for the development of metallic medical implants, but for high-risk implants like vascular support structures (stents), surface quality is critical to ensure successful implantation without harming the surrounding tissue and ensure the patients’ health. Therefore, enhancing the surface quality is crucial. Electropolishing is a method for removing surface roughness by smoothing out micro-peaks and valleys. However, L-PBF structures have a high surface roughness due to metal particles adhering on the surface. To achieve a smooth surface for additively manufactured implants like stents using electropolishing, the removal of these particles needs to be studied in more detail. The objective of this study is to examine the electropolishing mechanism of 316L stainless steel samples additively manufactured through Laser Powder Bed Fusion (L-PBF). The main objective is to investigate the removal properties and surface characteristics during electropolishing. To achieve this, various surfaces were characterized for morphology and roughness during Hull cell experiments. Markings are utilized on the Hull cell sample surfaces to identify points of interest during quasi-in-situ measurements. The surfaces are then analyzed after multiple time steps, applying different currents to investigate particle dissolution. The surface characteristics are analyzed through scanning electron microscopy, and surface roughness is analyzed using laser scanning microscopy. The results show that the electropolishing process preferentially removes the adhering particles present on the surface of the samples. Increasing the current density results in faster particle dissolution and a smoother surface (see Figure 1a and b). The mechanism of material removal of various surface features, as shown in Figure 1 (red circle, yellow arrow and red square), was assessed based on the experimental results of the surface structures seen on the SEM images. It was found that different surface features were removed during the experiment at different polishing times and current densities. The amount of charge flowed was found to correlate with surface morphology. Based on the obtained results, various surface features (such as large adherent particles, agglomerates of smaller particles, and valleys) and their changes with increasing test duration and current density were observed by quasi-in situ analyses. A reduction in the diameter of round particles adhering to the surface was observed at both low and higher current densities (see Figure 1a red circle a). Increasing the polishing time resulted in leveling of both large particles and valleys (see Figure 1b red square). Also, dissolution of agglomerates of smaller particles occurred at different polishing times as a function of current density and polishing time (see Figure 1a yellow arrow) are observed. Smoothed surface structures can be observed in regions with equivalent surface charge density (see Figure 2). As a result, comparable surface morphologies may appear at the same area charge density, irrespective of a specific current density. So, it may be adequate to only consider the amount of charge flowed to describe the electropolishing of additive materials. In conclusion, comprehending the dissolution characteristics of particles on L-PBF surfaces is essential for attaining satisfactory surface finish in electropolishing. The results of this study offer valuable perspectives into the electropolishing mechanism of additively manufactured 316L stainless steel and can guide future investigations on surface finishing and polishing of additive manufactured implants like stents. Figure 1 KW - General Earth and Planetary Sciences KW - General Environmental Science Y1 - 2023 U6 - https://doi.org/10.1149/MA2023-02241342mtgabs SN - 2151-2043 VL - MA2023-02 SP - 1342 EP - 1342 PB - The Electrochemical Society ER - TY - JOUR A1 - Grad, Marius A1 - Schultheiß, Ulrich A1 - Diemar, Andreas A1 - Spieß, Lothar A1 - Noster, Ulf T1 - Preparation methodology for the microstructural characterization of diffusion layers in a titanium/steel composite JF - Practical Metallography N2 - Hot pressing of titanium and carbon steel leads to the formation of a diffusion layer at the interface. Depending on the carbon content of the steel used, it either exclusively contains TiC or additional other phases. In the case of steel with a medium carbon concentration (0.67 wt.% C), a pure TiC layer forms. A preparation methodology was developed to make statements about functional and microstructural properties of the respective layers such as layer thickness, porosity, or grain size. However, apart from the diffusion layer’s microstructure, it also reveals the microstructure of the two base substrates. A comparison based on electron backscatter diffraction (EBSD) examinations yields similar results in terms of microstructure. A micrograph analysis based on the new preparation methodology also allows confirming the element distribution measurement by glow discharge optical emission spectroscopy (GDOES). The methodology therefore provides a way of quickly and reliably controlling the layer formation during the hot pressing process of titanium and carbon steel. N2 - Beim Heißpressen von Titan und Kohlenstoffstahl entsteht an der Grenzfläche eine Diffusionsschicht, welche abhängig vom Kohlenstoffgehalt des verwendeten Stahls entweder ausschließlich TiC oder zusätzliche andere Phasen enthält. Im Fall eines Stahls mit mittlerer Kohlenstoffkonzentration (0,67 wt.-% C) bildet sich eine reine TiC-Schicht. Um eine Aussage über die funktionalen und mikrostrukturellen Eigenschaften, wie Schichtdicke, Porosität oder Korngröße, entsprechender Schichten treffen zu können, wurde eine Präparationsmethodik entwickelt. Hierbei wird jedoch nicht nur das Gefüge der Diffusionsschicht, sondern auch das der beiden Grundsubstrate entwickelt. Ein Vergleich mit Elektronenrückstreubeugungs-Untersuchungen (EBSD) liefert hinsichtlich der Mikrostruktur vergleichbare Ergebnisse. Auch die Messung der Elementverteilung durch Glimmentladungsspektroskopie (GDOES) kann durch eine Schliffbildanalyse unter Anwendung der neuen Präparationsmethodik belegt werden. Die Methodik stellt also eine Möglichkeit zur schnellen und sicheren Kontrolle der Schichtbildung beim Heißpressen von Titan und Kohlenstoffstahl dar. T2 - Präparationsmethodik zur mikrostrukturellen Charakterisierung von Diffusionsschichten eines Titan-Stahl-Verbunds KW - Diffusion layers KW - TiC KW - microstructure KW - preparation methodology KW - EBSD KW - GDOES Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-78346 SN - 2195-8599 N1 - Corresponding author der OTH Regensburg: Marius Grad VL - 61 IS - 12 SP - 938 EP - 946 PB - Walter de Gruyter GmbH ER - TY - JOUR A1 - Esper, Lukas A1 - Schultheiss, Ulrich A1 - Grad, Marius A1 - Noster, Ulf A1 - Bund, Andreas T1 - Application of the Hull Cell for Identifying Electropolishing Parameters to Adjust Surface Morphology in Additive Manufacturing JF - ECS Advances N2 - Additively processed materials are increasingly used to manufacture customized parts, e.g. medical implants. Implant surfaces often require a smooth finish, which can be achieved by post-processing and well-defined process parameters. In this study, the effects of electropolishing of metal parts produced by laser powder bed fusion are investigated using Hull cell experiments and a three-electrode setup. Current density voltage curves were measured with the three-electrode setup to identify the regimes for electropolishing. Subsequently different constant-currents were applied and Hull cell experiments were conducted. The surface roughness (Sz, Sa) and the mass removal were analysed. Surface morphologies were assessed using laser scanning and scanning electron microscopy. A reduction of the initial surface roughness of more than 90% to Sa < 0.3 μm has been achieved. Considering the passed electrical charge during electropolishing, results from Hull cell experiments are systematically correlated with current-controlled electropolishing. This approach enables the precise tailoring of polishing parameters to achieve surfaces with defined roughness. Furthermore, the study demonstrates the suitability of Hull cells in determining electropolishing parameters for additive materials and highlights their contribution to post-processing in additive manufacturing. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-86295 SN - 2754-2734 N1 - Corresponding author der OTH Regensburg: Lukas Esper VL - 4 IS - 4 PB - The Electrochemical Society ER -