The influence of additive manufacturing on the micromilling machinability of Ti6Al4V: A comparison of SLM and commercial workpieces

Ti6Al4V produced by selective laser melting (SLM) is replacing the use of casting workpieces as it is a net-near shape process that can maintain its mechanical and biocompatibility properties and it can produce scaffolds geometry reducing the workpiece weight. Typically, the microstructure produced by SLM differs from casted workpieces, the surface roughness of SLM is also different is also higher compared to casted pieces. If it is needed precision and smooth surfaces, it is necessary to add machining after SLM, especially for the production of channels smaller than 1 mm, which is the case of micromilling. For the definition of micromilling, it is not recommended to use the ones indicated for meso scale and there are few studies on the micromilling of Ti6AL4V implants produced by SLM. This study compares the machinability of the standard commercial Ti6Al4V with produced by SLM during micromilling process using different feed per tooth configurations (from 0.5 to 4.0 μm). The analysis of machinability considered cutting forces, surface roughness, burr formation analysis and microchips morphology. Despite presenting higher strength and hardness, SLM material presented higher machinability with lower forces, lower surface roughness and less burs, explained by the SLM microstructural of fined acicular α’ martensite due to the rapid cooling of the material.