Investigation of mechanical behaviors of additively manufactured inconel 718 superalloys used in aerospace applications

Inconel 718 (IN718) is a nickel-based superalloy widely used in a variety of high temperature applications due to its outstanding mechanical properties and resistance to environmental degradation. It exhibits high strength, excellent fatigue and creep resistance, oxidation resistance and favorable weldability at elevated temperatures. IN718 has traditionally been produced and applied through forging, casting, and powder metallurgy. However, Additive Manufacturing (AM) is a new processing method that is gaining popularity in the aerospace, automotive, and defense industries. AM enables the production of complex geometries with high material utilization and shorter lead times compared to traditional methods. Among the various AM techniques, Selective Laser Melting (SLM) has shown potential for near net shape production of Ni based high temperature components, including IN718. SLM is a highly flexible and customizable AM technique, making it well suited for the production of complex critical parts, for example aero engine components. SLM uses a focused laser beam to selectively melt and fuse metal powders layer by layer according to a Three-Dimensional (3D) Computer Aided Design (CAD) model. However, parts produced using SLM often exhibit certain microstructural defects that can compromise their mechanical properties. These include residual stresses, porosity and microstructural defects such as grain boundaries and precipitates. To overcome these defects and improve the mechanical properties of SLM-produced (SLMed) IN718, post-heat treatment processes are used. This study examines the mechanical behaviour (tensile and hardness) of SLMed IN718 parts, taking into account the direction of fabrication and the heat treatments applied, including homogenization annealing and new aging. The findings offer valuable information for improving the fabrication process and achieving the desired mechanical properties in high-temperature components. Combining AM techniques with appropriate heat treatments has great potential for producing net-shape IN718 parts with complex geometries for high-performance requirements.