Microstructure- and defect-controlled damage tolerance evaluation of lattice structures at room temperature and 650 °C based on the E-PBF processed Ni-based alloy Inconel 718

• Applicants: Professor Dr.-Ing. Thomas Niendorf; Professor Dr.-Ing. Frank Walther
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Applied Mechanics, Statics and Dynamics
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 379213719

• Final Report Year: 2023

Final Report Abstract

The combination of Additive Manufacturing, specifically powder bed fusion of metals using electron beam (PBF-EB/M), and the high-temperature alloy Inconel®718 (IN718) enables innovative structural lightweight construction. By optimizing the design of components based on the flow of forces weight can be saved. The use of non-stochastic periodic lattice structures, instead of topology-optimized components, provides a promising approach to minimize the simulation effort for structural lightweight construction. IN718 is a precipitation-hardened hightemperature nickel-based alloy that undergoes an (intrinsic) strength-enhancing heat treatment during processing via PBF-EB/M. The use of IN718 in structural lightweight construction opens up numerous applications, e. g. in aerospace, as well as any purpose up to 650°C. In terms of durability, knowledge of the manufacturing process and its impact on component geometry, surface roughness, microstructure, and resulting mechanical properties is essential. Surface roughness is affected by the average powder particle size. Therefore, the search for suitable post-processing methods that ensure uniform and controlled material removal, even internally in a complex structure, is an important task. Characterization of mechanical quasi-static and cyclic properties at room and high temperatures, as well as evaluation of the microstructure stability at high temperatures, are necessary steps to qualify the use of IN718 lattice structures for structural lightweight construction.

Publications

• Effect of miniaturization and surface roughness on the mechanical properties of the electron beam melted superalloy Inconel®718. Progress in Additive Manufacturing, 5(3), 267-276.
  Kotzem, D.; Dumke, P.; Sepehri, P.; Tenkamp, J. & Walther, F.
  
• Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques. Materials, 13(1), 247.
  Kotzem, Daniel; Arold, Tizian; Niendorf, Thomas & Walther, Frank
  
• Influence of specimen position on the build platform on the mechanical properties of as-built direct aged electron beam melted Inconel 718 alloy. Materials Science and Engineering: A, 772, 138785.
  Kotzem, D.; Arold, T.; Niendorf, T. & Walther, F.
  
• Failure mode map for E-PBF manufactured Ti6Al4V sandwich panels. Engineering Failure Analysis, 121, 105159.
  Kotzem, D.; Tazerout, D.; Arold, T.; Niendorf, T. & Walther, F.
  
• Microstructure and strain rate-dependent deformation behavior of PBF-EB Ti6Al4V lattice structures. Materials Testing, 63(6), 529-536.
  Kotzem, Daniel; Gerdes, Lars & Walther, Frank
  
• Position-dependent mechanical characterization of the PBF-EB-manufactured Ti6Al4V alloy. Progress in Additive Manufacturing, 7(2), 249-260.
  Kotzem, Daniel; Höffgen, Alexandra; Raveendran, Rajevan; Stern, Felix; Möhring, Kerstin & Walther, Frank
  
• „Ganzheitliche Charakterisierung des Ermüdungsverhaltens PBF-EB-gefertigter Ti6Al4V-Gitterstrukturen“. Werkstoffprüfung 2021 - Werkstoffe und Bauteile auf dem Prüfstand, ISBN 978-3-941269-98-9, 74-79 (2021)
  Kotzem, D.; Raveendran, R. & Walther, F.
  
• Mechanical Assessment of PBF-EB Manufactured IN718 Lattice Structures. Proceedings in Engineering Mechanics, 3-18. Springer International Publishing.
  Kotzem, Daniel & Walther, Frank
  
• Electron beam powder bed fusion for direct microstructure design – In-depth analysis of prospects and limitations of the multi spot scanning strategy. Journal of Manufacturing Processes, 108, 485-497.
  Arold, Tizian; Suckau, Andreas; Böhm, Stefan; Krooß, Philipp & Niendorf, Thomas
  
• Ti6Al4V lattice structures manufactured by electron beam powder bed fusion - Microstructural and mechanical characterization based on advanced in situ techniques. Journal of Materials Research and Technology, 22, 2111-2130.
  Kotzem, Daniel; Arold, Tizian; Bleicher, Kevin; Raveendran, Rajevan; Niendorf, Thomas & Walther, Frank