Development and validation of a methodology for in-situ detection and model-based evaluation of manufacturing defects in electron beam powder bed fusion

• Applicants: Professorin Dr.-Ing. Carolin Körner; Professor Dr.-Ing. Frank Walther
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528264362

A significant advantage of additive manufacturing processes such as electron beam powder bed fusion (PBF-EB) is the possibility of manufacturing complex-shaped components without tools. However, due to the location-dependent process conditions, local defects occur in the manufactured components, which can currently only be detected by complex, non-destructive testing. At the same time, the influence of a defect on the performance of a complexly shaped component is strongly dependent on its characteristics (position, size, shape, orientation), for which only insufficient evaluation criteria currently exist. To overcome these limitations, this project aims to develop and validate a methodology that allows fracture-inducing defects in PBF EB to be reliably detected and characterized by means of electron optical (ELO) in situ imaging. Additionally, their quantitative influence on the local mechanical performance should be model-based evaluated. This should provide a solid criterion for evaluating individual defects and eliminate the need for additional non-destructive testing of the components. One goal of the first project phase is the development of an algorithm for the qualitative detection of misconnections from ELO signal data of the additive manufacturing process so that these can already be reliably detected during production. The characteristics of the defects will be detected subsequently by means of X-ray computed tomography and, together with the mechanical parameters of the investigated test specimens, will be used for validation and further development of defect- and microstructure-based models. The investigation will be carried out using the material system of titanium aluminides (TiAl), which is particularly sensitive to local defects due to their low defect tolerance and linear-elastic material behavior. By using the alloy BMBF3, which has been optimized for PBF-EB and has rarely been characterized so far, new material data will also be generated, which are necessary for the applicability of this promising material. In this context, extensive analyses at both research locations will enable an in-depth understanding of the relationships between process parameters, microstructure and defect formation as well as mechanical properties under near-application conditions and enable the transfer of the research results to other additively manufactured alloys. For this purpose, all test results, including process parameters, microstructure and defect analyses, mechanical properties (quasi-static and cyclic material behavior), and fractographic analyses, are combined in a digital twin of each specimen and used for the comprehensive analyses.

• DFG Programme: Research Grants