During the hot pressing of pure titanium and different carbon steels in a temperature range of $\vartheta$ = 950–1050 $°\mathrm{C}$, a compound layer up to d_L≈10 $\mu \mathrm{m}$ 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 $\mathrm{kJ}$ 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.

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.

Article Bauschingereffekt und mechanische Zwillingsbildung der Magnesiumlegierung AZ31 was published on June 1, 2003 in the journal HTM Journal of Heat Treatment and Materials (volume 58, issue 6).

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.

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.

New developments are needed in aortic replacement, with current hybrid solutions suffering from insufficient and rigid stent diameters, thus hindering minimization of false lumen in aortic dissection. Laser powder bed fusion (L-PBF) is an attractive method to generate a new-generation aortic stent. This study investigates the effects of 316 L stainless steel samples manufactured using the L-PBF process on the activity of fibroblasts, red blood cells, leukocytes and platelets on the modified surfaces. Cytotoxicity and hemocompatibility were analyzed under static culture conditions using immunofluorescence as well as scanning electron microscopic (SEM) techniques. Surfaces of additively manufactured samples were etched, electropolished, heat‑treated, and mechanically expanded to optimize the material’s mechanical performance. Alone heat treatment increased the ultimate tensile strength from 585 ± 5 MPa to 695 ± 6 MPa. The additive manufactured and post-processed stents were non-cytotoxic (viability, > 70%, independent of the manufacturing status), non-hemolytic (hemolysis rate, < 1%), and were covered with only a few neutrophils (median (IQR), 25 (12-48) per mm ² ) and platelets (cellular coverage, 0.5 - 10%). Material-induced formation of neutrophil extracellular traps (NETs) was low and not quantifiable. More than 80% of adherent platelets presented an activated conformation and increased expression of CD62P. In contrast, neither circulating leukocytes nor platelets in the supernatant showed any material-induced stimulation as detected via flow cytometry. The results described herein are encouraging and suggest that additive manufactured metallic stents are bio- and hemocompatible and an adequate candidate material for personalized stent production in a very short time.