Hybrid additive manufacturing of Ti6Al4V with powder-bed fusion and direct-energy deposition

A single component can often benefit from being built using more than a single processing technique. Here, we investigated the hybrid additive manufacturing (HAM) of Ti6Al4V using a combination of powder-bed fusion (PBF) and direct-energy deposition (DED). The aim was to identify critical areas and assess the performance of the hybrid process relative to the individual processes. The PBF sub-parts were built first, and then completed by DED. The builds were in the horizontal and vertical directions, so we could observe the mechanical anisotropy relative to the build direction. X-ray computed tomography, microstructural examinations, and tensile testing coupled with digital image correlation were employed to assess the parts. The as-built PBF surface can be used to build HAM Ti6Al4V samples with DED, thus eliminating steps like machining. The HAM samples built in horizontally had intermediate tensile strengths of about 1050 MPa, and in the vertical direction, about 860 MPa, i.e., lower than the DED samples. Strength-wise, horizontally built parts exceeded the requirements. However, a reduction in deposition size (especially <102 mm2) promoted a different temperature evolution and, in the worstcase scenario, heat accumulation, which led to the formation of an undesirable microstructure and local plastic deformation in the DED part.