In Additive Manufacturing (AM) of metallic structural alloy components, laser printing parameters influence defect formation (pores and lack-of-fusion defects) and microstructural evolution (grain size, morphology, and orientation), which, in turn, determine the mechanical properties of the material. For this study, five specimens of Ni-based alloy, Hastelloy-X, were printed using selective laser melting (SLM), with varying volumetric energy density (VED)from 146 to 58 J/mm3. These specimens were studied using synchrotron x-ray computed micro-tomography for internal defect imaging and synchrotron x-ray diffraction for texture and phase analyses. Qualitatively, tomography data shows that a decrease in VED causes an increase in porosity, in both pore size and density, and lack-of-fusion defects. The relationship between AM processing conditions, defect structures, and microstructural development will be determined to understand how basic mechanical integrity can be influenced by key printing parameters.