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Comparison between EBM and DMLS Ti6Al4V Machinability Characteristics under Dry Micro-Milling Conditions

This paper is aimed at evaluating the micro-machinability of the Ti-6Al-4V titanium alloy made by the means of two different Additive Manufacturing (AM) technologies. AM comprises promising technologies, widely used especially to produce parts made of difficult-to-cut materials, such as the titanium alloys. Titanium alloys represent one of the most widely used materials in the biomedical field, thanks to the high biocompatibility and excellent mechanical characteristics. Even if near-net-shape parts can be produced through AM, semi-finishing and/or finishing machining operations may be necessary to obtain the required surface finish and geometrical tolerances. Micro-milling technique is a soliciting solution for this kind of application due to its high flexibility, elevated material removal rate and direct contact between the tool geometry and work piece. Nevertheless, there are deficiencies in the literature regarding the study of micro-machinability of materials produced by means of AM technologies. In this paper, the micro-machinability of the Ti-6Al-4V alloy obtained by two different AM technologies, namely Electron Beam Melting (EBM) and Direct Metal Laser Sintering (DMLS), was studied and compared in order to assess the influence of the material as-delivered condition. Micro-milling tests were conducted on a high-precision 5-axis Kugler™ micro-milling centre under dry cutting conditions, by using uncoated, two fluted, flat-end-square, tungsten carbide tools with a diameter of 300 microns. The full immersion slotting strategy was chosen under full factorial design of experiments with two factors (cutting speed and feed per tooth). The micro-machinability was evaluated in terms of burr formation, surface integrity (surface topography and surface defects), tool damage and microstructure alterations.