Microstructural characterization and surface integrity of additively manufactured Inconel 718 alloy

Selective laser melting is increasingly used to produce Inconel 718 components for aerospace, energy, tooling, and other demanding engineering applications. In these fields, material efficiency, component reliability, and long service life are closely linked to more sustainable manufacturing. However, the practical application of the produced parts depends on identifying processing conditions that ensure successful fabrication, surface integrity, and microstructural quality. In this study, the relationship between process feasibility and the surface–microstructure–property response of Inconel 718 was investigated. Specimens were fabricated using laser powers of 200–400W, scan speeds of 675–1200mm/s, and layer thicknesses of 0.03–0.06mm. Out of 27 designed parameter combinations, 19 specimens were successfully produced and further evaluated in terms of surface roughness, porosity, hardness, and microstructure using optical profilometry, Archimedes measurements, Vickers hardness testing, optical microscopy, SEM/EDS, and EBSD. The results showed that the surface roughness increased mainly with layer thickness, with the scanning direction surface being smoother than the build direction. Porosity ranged from 0.031% to 5.174%, and the maximum hardness reached 345.2HV10, with higher hardness generally associated with lower porosity. Microstructural observations revealed melt-pool boundaries, dendritic/cellular features, micropores, cracks, and local Nb- and Mo-rich regions. EBSD analysis showed that lower layer thickness promoted finer grains and weaker <001> texture, whereas thicker layers resulted in coarser grains and stronger texture development. By linking build feasibility to directional surface roughness, porosity, hardness, and microstructural characterization, this study provides a machine-specific processing framework to improve the reliability and resource efficiency of SLM-produced Inconel 718 components.