As-built microstructure and mechanical behavior of Inconel 718 processed via directed energy deposition with laser beam

Abstract

Inconel 718 (IN718) is a Ni–Cr–Mo-based superalloy widely used in aerospace applications due to its excellent mechanical properties and corrosion resistance at high temperatures. Its high strength, however, presents challenges for conventional manufacturing of complex geometries due to its poor machinability. Additive manufacturing (AM), mainly directed energy deposition with laser beam (DED-LB), has emerged as a promising solution, offering precision, reduced material waste, and design flexibility. The microstructural evolution of IN718, primarily influenced by the precipitation of secondary phases such as γʹ, γʺ, Laves phases, and carbides, is critical for its performance. This study successfully developed a process window for DED-LB, producing high-density samples with minimal defects. Microstructural analysis revealed the role of grain size, second phases and Laves phases. At the same time, mechanical testing demonstrated a balance between strength and ductility, attributed to precipitation hardening and the predominance of screw-type dislocations. This work investigates the as-built condition of IN718 to evaluate the direct impact of process parameters on microstructure and mechanical properties without the influence of post-processing treatments. Key findings include the correlation of grain morphology and defects to the mechanical behavior of as-built samples. The results provide insights into the microstructural evolution and mechanical performance of DED-LB IN718 in the as-built condition.