Effects of machining surface and laser beam scanning strategy on machinability of selective laser melted Ti6Al4V alloy in milling

Overlapping melting trajectories and partially-melted powders result in poor surface morphology and high surface roughness values (Ra = ~13.34 μm) of selective laser melted (SLMed) Ti6Al4V alloy. Secondary processing of SLMed components is thus an essential finishing operation to produce functional SLMed parts in precision engineering. This paper investigates the effects of laser scanning strategies (0°, 67.5° and 90° laser scanning schemes) and machining surfaces (top and front surfaces) on the machining performance of SLMed Ti6Al4V alloy in milling, compared with that of annealed ASTM B265 Ti6Al4V alloy. High degree of anisotropy of SLMed Ti6Al4V alloy is reflected in cutting force, surface morphology and surface roughness on different machining surfaces. The machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy, where the anisotropy weakens following the sequence of 0°, 90° and 67.5° SLMed samples. It is verified that high cutting speed can improve machining anisotropy features of SLMed titanium alloy. The chip shape of SLMed Ti6Al4V alloy is a typical conical spiral chip, and the bending degree and length of chips produced by SLMed Ti6Al4V alloy are larger than those produced by annealed Ti6Al4V alloy. [Display omitted] •Grain on top surface of SLMed Ti6Al4V is close to {21¯1¯0} while that on front surface is inclined to {101¯0} and {0001}.•Machining anisotropy is dominated by the anisotropy of microstructure and mechanical properties of SLMed Ti6Al4V alloy.•Surface quality on top surfaces of 0° and 90° SLMed Ti6Al4V is significantly better than that on front surfaces.•The bending degree and length of SLMed Ti6Al4V alloy chips are larger than those of annealed Ti6Al4V alloy.