Residual stress generation in generative and regenerative arc-based additive manufacturing with transformable steel

• Applicants: Professor Dr.-Ing. Klaus Dilger; Dr.-Ing. Jens Gibmeier
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542533151

In the planned research project, a fundamental understanding of the component-related manufacturing influences on the material properties and in particular the development of residual stress in the generative and regenerative production of large-volume components using DED-Arc (Direct Energy Deposition Arc) will be developed. During the fundamental investigations, the influences of energy input and temperature control in the construction process on productivity, material behavior as well as the formation of residual stresses and the associated distortion are determined and quantitatively described. This is achieved through a combined consideration of the process characteristics, the material properties and local real-time insights into the stress generation during DED-Arc processing using in situ synchrotron X-ray diffraction analyzes as well as the implementation of the experimental test data in a numerical prediction model (FEM) to describe component-integral relations. The in situ diffraction analyzes determine valuable time-resolved process data, which can be used to validate and improve the process predictions using FE simulation. The result is quantitative knowledge of the fundamental cause-effect relationships between energy and material input, temperature control and geometry-dependent restraints on the resulting internal stresses and distortions in structures manufactured via DED-Arc. Based on these findings, it will be possible to choose a suitable manufacturing strategy to minimize manufacturing-related residual stresses of complex components (scope of the project continuation). Since the focus of the project is on the functionalization and repair of components, additive welding is carried out in (regenerative) or on (generative) an existing structure made of hot-work tool steel X37CrMoV5-1. The martensitic transformation steel Fe8 according to DIN EN 14700 is used as a welding filler material in the form of a solid wire electrode. For the systematic approach to project processing, three basic geometries were selected (thin-walled plate, tube geometry and circumferential wall structure on a shaft), which allow individual geometric features of complex components to be examined separately. The basic geometries were defined selected so that they differ fundamentally in the shrinkage related restraints present. Based on possible modification and repair tasks, the material deposition of a developed (fictitious) defect is also examined for the basic geometries under consideration with a view to restoring the geometry. In accordance with the general process chain for repair applications, the investigations consider both, the condition after the near-net-shape material has been applied and the state after surface machining.

• DFG Programme: Research Grants