Mechanical and Fracture Properties of As-Built Inconel 718 Produced by High-Speed Laser Directed Energy Deposition: Stability to Process Parameters Variation

Directed energy deposition (DED) is a group of efficient additive manufacturing methods for creating complex-shaped components. Of these, the next-generation high-speed laser-based directed energy deposition (HS DED-LB) combines high-speed kinematics and a high-power infrared laser, offering unparalleled deposition speeds. Due to its novelty, the mechanical and fracture properties of the HS DED-LB deposits are virtually unknown. In this pioneer study, a series of unique testing methods was used to determine the properties and assess the influence of the inherent microstructure. As a model material, Inconel 718 was selected as an industrially relevant superalloy. To demonstrate the HS DED-LB capabilities, it was printed at a high powder feed rate of 30 g/min at different levels of laser power (up to 2400 W) and scanning speeds (up to 60 m/min). The corresponding linear energy densities ranged from 1.8 to 3.6 kJ/m, i.e., values significantly higher than those of powder bed fusion methods and lower than those of conventional DED. The method was shown to be very robust as, in this range, the tested mechanical and fracture properties differed by less than 10%. The HS DED-LB Inconel 718 exhibited a specific microstructure and texture, owing to the inherent thermal history of the melt pool. This is a favorable material state, similar to that of the traditional directionally solidified Inconel superalloys used in aerospace.