Machine hammer peening of laser deposition welded IN718 components (MalIn)

• Applicant: Professor Dr.-Ing. Thomas Bergs
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452669313

IN718 is a precipitation-hardenable nickel-chromium alloy which exhibits high strength and ultimate elongation even at high temperatures. Targeted adjustment of the IN718 material structure can significantly improve the mechanical properties of the component, both wear resistance and fatigue strength.Today, the blanks for the later IN718 components in the aerospace industry are mainly produced via the process chain of casting, forging and pre-turning. Especially the repetitive forging operations have a decisive influence on the excellent IN718 material properties. The blanks are then machined in a variety of machining operations, which account for a large proportion of the total manufacturing time and cost. The high tool wear rates and cutting volumes of over 90% in some cases lead to a reduced economic efficiency of this process chain. Additive manufacturing processes offer an alternative at this point.Additive processes such as laser deposition welding of wire offer the possibility of near-net-shape production. The coarse-grained, anisotropic microstructure that forms as well as the tensile residual stresses and solidification shrinkage that occur during the welding process lead not only to unfavorable mechanical component properties but also to geometrical deviations and poor surface quality. The component properties resulting from laser deposition welding can be improved by means of forming manufacturing processes.Since the surface layer of technical components is often the area most heavily stressed and significantly influences the overall component function, local forming with surface treatment processes such as shot peening, deep rolling or machine hammer peening (MHP) is a suitable option. Depending on the process, the component surface can be smoothed, compressive residual stresses induced and strain hardening introduced into the component surface layer. While especially deep rolling in additive manufacturing is already state of the art, the cause-effect relationships between the innovative MHP and the surface layer morphology, especially the microstructure and surface topography, of additive workpieces are still unexplored.In order to enable a purposeful process combination of wire laser deposition welding and MHP process with regard to improved mechanical properties resulting from a specifically adjusted surface layer morphology, the basic cause-effect relationships between the process parameters of laser deposition welding and MHP and the surface layer properties must first be explained.

• DFG Programme: Research Grants