Effect of oxygen content of tantalum powders on the characteristics of parts processed by laser powder bed fusion

In this study, spherical tantalum (Ta) powders, having different oxygen contents, were fabricated by a radio frequency plasma spheroidization technique. A laser powder bed fusion (LPBF) technique was then used to consolidate these powders and the effects of different LPBF processing parameters on the densification, microstructure and mechanical properties of parts were investigated. The results indicated that the oxygen content of the used Ta powder has significant influences on the densification, microstructure and the consequent mechanical properties of printed parts. The relative density of the parts printed from the powders with a low oxygen content of ∼150 ppm was insensitive to the applied laser energy density and was higher than the ones prepared from the powders with higher oxygen contents. The grain refinement was observed and the texture in the side-view of the as-built samples changed from {100}∥BD to {111}∥BD with the increase in the oxygen content of the used powders. The microhardness and ultimate tensile strength of samples increased and the ductility of parts decreased with the increase in the oxygen content of the used raw powders. The main fracture mode of the LPBF consolidated Ta samples changed from a typical ductile rupture to the combination of cleavage and ductile rupture modes with the increase of the oxygen content in the processed parts.