The printability, microstructure, crystallographic features and microhardness of selective laser melted Inconel 718 thin wall

Abstract The thin plate is a promising light-weight structure to broaden applications of Inconel 718 superalloy in aerospace and transportation industries. In the present work, selective laser melting (SLM) technology was applied to manufacture a series of Inconel 718 thin walls (ultra-thin plates) to explore their printability, microstructures, crystallographic features and microhardness under keyhole and conduction modes. Results show that it is feasible to manufacture Inconel 718 thin walls with a thickness of ~0.2 mm by SLM. Keyhole mode is favorable for a better printability, finer dendrites, the precipitation of strengthening phases of γ′/γ″, a stronger 〈001〉 texture intensity and a higher microhardness in the center zone of the SLMed thin wall. Conduction mode contributes to the uniform microstructures and microhardness in the marginal and center zones of the thin wall. Also, the decrease of area fraction in strengthening phases and the increase of Laves phase result in a decreasing trend of microhardness along the deposition direction. Finally, microstructural formation and evolution mechanisms of SLMed thin walls under two modes are proposed based on the solidification conditions and vertical thermal cycles.