Machinability analysis for milling of additively manufactured Inconel 718 with specifically induced porosity

Compared to conventional manufacturing technologies, additive manufacturing (AM) offers great design freedom, the integration of functions into components, new lightweight construction concepts and high material efficiency. This technology is increasingly coming into focus in aerospace and turbomachinery engineering, especially the Laser Powder Bed Fusion (LPBF) process. LPBF is already being used for some aerospace components that are often subject to high thermal and mechanical loads. Depending on the component geometry, support structures are required for additive manufacturing, which then have to be removed, usually by machining. Among others, the use of material with specifically induced porosity is suitable as a support structure. This ensures good heat dissipation and thus homogeneous component properties, high retention forces and short process times in the LPBF process. However, the machinability of porous, additively manufactured material has hardly been researched to date. This paper therefore presents the results of machinability investigations with porous, additively manufactured Inconel 718. The investigations included the analysis of active cutting force, cutting tool wear, surface finish and chip geometry in the milling process with tungsten carbide cutting tools. It was found that with the porous material, the dominant type of wear is early starting chipping of the cutting tool edges. The active force decreases with increasing porosity. Partial smearing of the pores was observed on the milled surfaces. The chips of the porous material show a disrupted surface. In future investigations, the aim is to improve the wear behaviour when milling porous Inconel 718.