Dr.

Hein, Sebastian Boris

Filters

24
Reset filters

Settings
Now showing 1 - 10 of 24
  • Publication
    Curing Behaviour of Non-Corrosion-Resistant Tool Steels in Metal Binder Jetting
    ( 2023-10)
    Wieland, Sandra
    ;
    Reineke, Lea
    ;
    Eckel, Julius
    ;
    Giel, Jonathan
    ;
    Hein, Sebastian Boris
    Along the Metal Binder Jetting process chain, the metal powder is subjected to interactions with the binder, which is often water-based, and with air at elevated temperature during the curing step. This can lead to corrosion or oxidation reactions, especially for non-corrosion-resistant materials like typical tool steels. In order to investigate the interaction of non-corrosion resistant steels and different binders as well as the curing behaviour, two commonly used tool steels (PM-V10 and M2) are combined with three different binders. Measurements are carried out on the wetting behaviour of all powder-binder combinations, by determining the saturation rate and equilibrium binder saturation. Curing temperatures are set according to the respective binder composition, and both curing in air as well as in protective atmosphere is tested. The evaluation includes the shape of the resulting green parts and the density, microstructure, and carbon and oxygen content of parts after debinding and sintering.
  • Publication
    Use of high Melt Flow Rate Poly(oxymethylene) in Binders for Metal Injection Moulding Feedstocks
    ( 2023-10)
    Hein, Sebastian Boris
    ;
    Min, Young Doo
    ;
    Luoto, Mikael
    Poly(oxymethylene) (POM) is widely used in for metal injection moulding (MIM) feedstocks, due to its high strength and clean removability. The intent to use high melt flow rate POM was to improve processability, enabling more intricate parts, or processing at lower process temperatures. The processability of different feedstocks, prepared with such a POM-type, was investigated regarding the effects of metal powder type (316L, 17-4 PH), particle morphology (gas- and water-atomized), as well as different mixing procedures (ZX-blade mixer with and without subsequent shear roll extrusion). Feedstocks of all variations could be processed properly, but the most promising results were shown by feedstocks using gas-atomized powders and both mixing procedures. In that case, due to the good flowability, the feedstock injection step was very smooth and led to the smallest process deviations. This was shown by analysing the process data and the characterization of green and sintered parts.
  • Publication
    Integration of In Situ Measurements to Monitor the Print Process in MBJ
    ( 2023-10)
    Hein, Sebastian Boris
    ;
    Reineke, Lea
    ;
    Cogotti, Andrea
    ;
    Gerken, Felix
    ;
    Sandmann, Malte
    Metal Binder Jetting (MBJ) gains increasing industrial attention due to its serial production potential. In order to tap the full potential of MBJ, a deep process understanding is crucial. The aim of this work is to gain a deeper insight of the influence of process parameters on the powder spreading and powder bed heating by using in situ measurements, as a way to create a basis for real-time process control and optimization. This is achieved by generating images of the powder build-up in front of the spreading roller and thermal imaging of the powder bed for each layer. An automated image processing was developed to examine the powder build-up, and the green part properties were evaluated with different powder heating settings respectively. A proper control of the powder spreading and powder bed temperature positively influences powder binder interaction and green part properties, while minimizing the scrap rate.
  • Publication
    Influence of Powder Packing Density on Binder Saturation and Wetting Behavior in Metal Binder Jetting
    ( 2023-10)
    Reineke, Lea
    ;
    Schlegel, Regina
    ;
    Hein, Sebastian Boris
    Metal Binder Jetting (MBJ) has an increasing attention in additive manufacturing because of its serial production potential. Finding the most suitable parameterization in MBJ and develop pre-printing tests, can reduce the iteration stages in material-specific process development, which saves costs, effort as well as material resources and printing capacity. The powder binder interaction of five powders at different packing densities were determined and the wetting behaviors were compared. The equilibrium saturation, the wetting rate and the initial wetting time were analyzed. In order to understand the nature of the resulting porosity at low packing density, various samples were sintered and compared by micrographs. The results show that an increasing packing density decreases the initial wetting time, increases the equilibrium saturation and lowers the saturation rate. The relationship between wetting behavior and printing parameters, as well as the effect of drying must be investigated further in subsequent studies.
  • Publication
    Investigation of Binder Droplet Impact in Metal Binder Jetting
    ( 2023-10)
    Norda, Michael
    ;
    Reineke, Lea
    ;
    Wonn, David
    ;
    Hein, Sebastian Boris
    The metal binder jetting (MBJ) process is a powder bed-based Additive Manufacturing (AM) process, which is attracting growing interest. In this process, a liquid binder deposited by a print head is bonding the powder particles to create green parts, which are then consolidated by a subsequent sintering step. The parameters of this liquid deposition are crucial for high quality parts because the droplet impact influences the porosity of the parts. In this work, different droplet volumes are investigated by using two print heads in order to describe the influence of the size, weight and amount of the droplets on the parts quality. The experiments are conducted using 316L stainless steel in two different sizes and a titanium alloy Ti6Al4V. Several properties of powders and parts are analysed such as powder size distribution, green part density, powder bed density and bending strength. Furthermore, drop watcher analyses were conducted. The results show that the print head with lower drop volume introduces more porosity in the green part compared to the higher version. Also, they show higher strength values during the bending tests. The drop watcher analyses indicate that the drops can be very irregular in size, trajectory, and velocity. The fire frequency, voltage and pulse width needs to be adjusted accordingly. Further research can be carried out using optimized firing parameters for the print heads.
  • Publication
    Microstructural development during additive manufacturing of biomedical grade Ti-6Al-4V alloy by three-dimensional binder jetting: material aspects and mechanical properties
    ( 2023)
    Simchi, Abdolreza
    ;
    Petzoldt, Frank
    ;
    Hartwig, Thomas
    ;
    Hein, Sebastian Boris
    ;
    Barthel, Bastian
    ;
    Reineke, Lea
    Additive manufacturing (AM) of biomedical materials provides enormous opportunities to fabricate multifunctional and structurally designed frameworks for tissue engineering, such as dental implants and bone substitutes. Despite several advantages of the binder jet 3D printing technology over other AM methods, for example, no limitations in materials selection, high materials recycling efficiency, no thermal stress development, no need to support materials, and the possibility of fabrication of printing functionally graded materials, the fabrication of biomedical-grade titanium alloys with high-density, fine microstructure, and low pickup of impurities is still challenging. This work presents the effects of powder particle size and 3D printing conditions on the microstructural features and mechanical properties of Ti-6Al-4V alloy. The formation of large and inter-aggregate pores during binder jetting is demonstrated and discussed. Design and selection of particle size distribution with a mean diameter of ~20 μm and large span and positive skewness are proposed to minimize binder-induced powder aggregation and fabricate green parts with a density of 65±1% PFD (pore-free density). Dilatometric studies under a partial pressure of argon (0.1 bar) determine that sintering just above the α/β transus temperature (~980 °C) provides a high strain rate to remove pores, but high-temperature sintering (≥1250 °C) is required to attain 97% PFD. The successful fabrication of high-density Ti-6Al-4V parts (≥96% PFD) with the microstructure comparable to metal injection molding (MIM) titanium parts (≈100 μm α grains + β lattes) is demonstrated. The tensile strength and elongation values fall in the range of 880±50 MPa and 6±2% (depending on the processing condition), which is comparable with metal injection molded parts and superior to the laser powder bed fusion technology concerning ductility. The content of carbon (<0.02 wt.%) and nitrogen (0.01 wt.%) also falls in the standard region of metal injection molding. However, oxygen pickup during sintering moderately increases the oxygen content (for 30–50%) over the standard level. The concentration of interstitials entrapped in the metal is comparable to that of parts manufactured by the powder bed fusion process, but the mechanical properties are better matched with the commercial titanium alloy. The fabrication of the titanium alloy as per the ASTM F2885 standard provides an excellent opportunity for the binder jetting process to develop custom-made biomaterials.
  • Publication
    Evaluation of the Processing Capability of Aluminium Alloy 6061 for Metal Binder Jetting
    ( 2021)
    Wieland, Sandra
    ;
    Hein, Sebastian Boris
    ;
    Weber, David
    Sinter-based Additive Manufacturing (AM) processes such as Metal Binder Jetting (MBJ) combine the advantages of AM, such as freedom of design and low material loss, with comparatively high economic efficiency. However, sintering of aluminium and aluminium alloys is challenging due to the stable oxide layer, and is becoming even more difficult by the addition of an organic binder. In this work, several commercially available 6061 powders in a particle size range suitable for MBJ have been investigated regarding their processing capability. After analysing the sinterability of loose powder at different temperatures and atmospheric conditions, MBJ binder was added to study the influence of the organic components and various debinding conditions. The powder which achieved the highest sintered density was selected for MBJ trials, and the resulting green and sintered density of simple test parts was investigated.
  • Publication
    Influence of Particle Size Distribution in Metal Binder Jetting - Effects on the Properties of Green and Sintered Parts
    ( 2019)
    Barthel, Bastian
    ;
    Hein, Sebastian Boris
    ;
    Aumund-Kopp, Claus
    ;
    Petzoldt, Frank
    In binder jetting, parts are build layer-by-layer in a powder bed by locally printing an organic binder. After curing the binder, the green parts are cleaned of the loose powder. A combined furnace process removes the binder and fuses the particles together. The microstructure of a sintered part depends on powder properties, green part density and sintering parameters. The influence of the particle size distribution (PSD) on the sintering behaviour is widely known. With decreasing particle size, the sintering activity increases. This enables a reduction of the sintering temperature and reduces the distortion potential. Finer powders have higher capillary forces and tend to agglomerate, which affects packing density and flowability. This paper takes a closer look at the influence of PSD and layer thickness on density and dimensional accuracy of the green parts. The effects on shrinkage behaviour and sintering density of binder-jetted parts are also shown.
  • Publication
    Additive Manufacturing of Functional Metallic Materials
    ( 2019)
    Wieland, Sandra
    ;
    Goossens, Nils
    ;
    Weck, Christian
    ;
    Hein, Sebastian Boris
    Additive Manufacturing (AM) has become increasingly popular during the recent years, but up to now AM research is mainly focused on structural applications. However, the advantages of AM technologies, as the ability to realise optimized designs with reduced material consumption, apply similarly for functional metallic materials. Additionally, for some materials the specific microstructure formed by an AM method can be beneficial for the functional properties or for further processing steps. Utilizing this advantages, AM could significantly promote getting innovative materials which are difficult to produce or machine into practical application. A brief overview on the status of AM of functional materials will be given and potentials and challenges will be illustrated by the cases of Laser Beam Melting of soft magnetic Fe-Ni-alloys and magnetocaloric La(Fe,Si)13-alloys.
  • Patent
    Verfahren zur Herstellung von Wendeln
    ( 2019)
    Wöstmann, Franz-Josef
    ;
    Kramer, Lutz
    ;
    Heuser, Michael
    ;
    Hein, Sebastian Boris
    ;
    Mulser, Marco
    ;
    Hartwig, Thomas
    Die Anmeldung betrifft ein Verfahren zur Herstellung metallischer Wendeln, sowie die in dem Verfahren hergestellten Wendeln. Das Verfahren umfasst die folgenden Schritte: Bereitstellen einer wendelförmigen Kavität (1.1) in einem Spritzgießwerkzeug; Füllen der Kavität (1.1) mit einer ein Pulver aus einem sinterfähigen Material enthaltenden Formmasse; Herstellen eines Grünteils (2) durch Erstarren der Formmasse; Entnehmen des Grünteils (2) aus dem Spritzgießwerkzeug; Entbinderung des Grünteils (2); Sintern des Grünteils (2).