Device for laserbased powder bed fusion for additive manufacturing

• Subject Area: Materials Science
• Term: from 2022 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 513459481

The additive manufacturing (AM) of functional magnetic materials is still in its infancy. The reasons are threefold: (a) functionality depends on interface, structure, defect and chemistry control on the nanoscale in the bulk or printed parts, from intrinsic magnetic to extrinsic properties, (b) the availability of adequate powder precursors and (c) AM systems which provide the necessary conditions for processing functional materials. Here we apply for a laser powder bed fusion (L-PBF) device with an adaptive building chamber system including atmosphere control with lowest oxygen fractions (< 25 ppm), a building volume reduction for the use of several 100 grams of powder and a heating stage reaching temperatures up to 1200°C. With this, we will gain fundamental insights into the metal powder laser processing of functional and fully dense magnetic materials like high performance permanent magnets. Targeted are fully dense printed parts of specific chemical composition that allow the geometrical design of physical properties such as magnetic stray fields or electrical and thermal conductivity of the functional material used. The requested system offers the use of lab scale produced metal powders of functional materials for standard testing and qualification procedures. We managed to develop a qualification procedure for small powder amounts of roughly 100 grams even with non-spherical particle shape in a rather broad size distribution, which allows a scientific material screening at reasonable costs. To increase the powder screening opportunity, a flexible system for quick powder change is required. Furthermore, a sieving system is necessary to separate the fine particle fraction from the powder used during the L‑PBF process. An external device, which allows easy accessibility and cleaning, is preferable for processing different powders. The process monitoring options are of high importance (melt pool management) which have to be directly included into the recursive material design process. Specifically, the monitoring of thermal fluctuations (using a pyrometer) and the melt behaviour (CMOS high speed camera) are necessary to evaluate the print. The power input can be regulated by the laser parameters, which in combination with the powder bed temperature opens a new parameter space for the usually difficult to print materials by reducing crack formation in the mostly brittle intermetallic compounds. In summary, the described device offers the possibility to monitor and evaluate the complex melting behaviour of functional materials with the presented monitoring possibilities. The rapid and wide-ranging adaptation of laser parameters and build volumes to novel material powders is indispensable for systematic research on resource critical materials and will enhance the collaboration between the research partners in the fields of materials science and mechanical engineering.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Maschine zur Laser-Pulverbett-Fusion für die additive Fertigung
• Instrumentation Group: 5740 Laser in der Fertigung
• Applicant Institution: Technische Universität Darmstadt
• Leader: Professor Dr. Oliver Gutfleisch