Machinability of SLM-produced Ti6Al4V titanium alloy parts

Due to its vast benefits, Additive Manufacturing (AM) has attracted a great deal of attention during the last two decades. Selective Laser Melting (SLM) is one of the most increasingly used AM techniques in the world. The machinability of SLM-manufactured Ti6Al4V parts in as-built (SLM-AB) and stress-relief (SLM-SR) conditions was studied in this work via toroidal milling. A conventional processed Ti6Al4V alloy was tested as a reference. SLM process parameters for producing near fully dense parts were optimized to yield a volumetric energy density of 46.4 J/mm3. Relative density, microstructure, hardness, residual stresses, surface roughness, cutting forces, tool wear, and chip morphology were evaluated. The SLM-manufactured parts gave a relative density of 99.70 % and higher hardness values than those of the conventional parts by a factor of about 1.2. The conventional, SLM-AB, and SLM-SR Ti6Al4V alloys exhibited microstructures consisting of α and β phases, acicular α′ martensite, α′ martensite and some amounts of α + β phases, respectively. The conventional alloy had the lowest residual stress. SLM-AB had considerable residual tensile stress in the 0° direction of measurement, whereas SLM-SR had the highest compressive stress in both 0° and 90° directions. The lowest cutting force was observed in the conventional alloy and the highest in the SLM-SR alloy. The SLM-AB alloy featured the highest flank wear. However, no significant difference in flank wear was observed in the conventional and SLM-SR alloys.