Fundamental investigation of powder smoking phenomenon during selective electron beam melting

• Applicant: Professorin Dr.-Ing. Carolin Körner, since 1/2023
• Subject Area: Production Automation and Assembly Technology ; Chemical and Thermal Process Engineering ; Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448758899

Selective Electron Beam Melting (SEBM) is one of the most promising additive manufacturing technologies for producing high-performance materials, owing to its fast control of the beam position, high power output and energy absorbance as well as low oxidation and contamination risk. Nevertheless, the so-called smoke phenomenon, which results in an explosion-like powder spreading within the whole machine, restricts the further development of SEBM of different materials. So far, methods to prevent smoke event are mainly based on trial-and-error optimization and empirical rules. A basic understanding of powder smoking mechanism is highly desired to exploit the potential of the SEBM process. According to experimental observations at the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and at the TsingHua-University (THU), the proposed project is based on the novel hypothesis that powder smoking is initiated by gas evaporation, which can take place at relatively low temperatures under vacuum conditions, followed by an avalanche effect caused by electrostatic charging of the powder bed during SEBM. At FAU, the research focus will lie on the investigation of the effect of gas evaporation, while THU will be committed to discover the influence of powder bed charging during SEBM. Main objectives of the project are to in situ observe the evolution of the whole smoking process and to establish a physical model to explain the smoking mechanism as well as to prevent the powder smoking. First, far-field and near-field ELectron-Optical (ELO) observation system as well as other different process monitoring tools will be used for the in situ observation of smoking at FAU and THU, respectively. Second, in order to evaluate key factors leading to smoking, the effect of powder properties (at FAU) and process parameters (at THU) will be investigated. Third, for physical modelling, recoil pressure induced by gas evaporation (at FAU) and electrostatic repulsive forces caused by powder bed charging (at THU) will be taken into account. Finally, optimized scan strategies and requirements on powder properties can be derived to increase process stability and to allow the use of finer powders. In addition, by analyzing ELO signals a real-time signal processing system will be developed, so that the SEBM process can be promptly interrupted at the initial stage of powder smoking, before the avalanche effect (catastrophic smoke event) occurs.

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partner: Professor Feng Lin, Ph.D.
• Ehemaliger Antragsteller: Dr.-Ing. Zongwen Fu, until 12/2022