Publication

Abstract : The significant characteristics of the nickel-based Inconel 718 (IN718) superalloy are high strength, fatigue capacity, rupture strength, corrosion resistance, and creep resistance at temperatures exceeding 650 °C, which opens the application of IN718 for aircraft parts. The mechanical properties and surface residual stress (SRS) of the IN718 superalloy have been affected by fabrication and post-processing procedures, which shorten the service life of components. For the fabrication of complex aviation components, additive manufacturing of aerospace materials like IN718 has opened up new production techniques. However, localized melting and solidification produce anisotropy microstructure and a crystallographic texture with substantial tensile residual stress. These are responsible for mechanical anisotropy and pose metrological challenges for diffraction-based SRS detection. Knowing the magnitude and nature of SRS is crucial since they affect a mechanical properties and life of the parts. In this study, IN718 alloys were fabricated using the laser-based powder bed fusion (L-PBF) technique, and the impact of the standard ageing heat treatment (SAHT) process was assessed. The as-fabricated (AF) IN718 microstructure was found to have columnar dendritic structure and Laves phases in the interdendritic regions along the build direction. The SAHT sample microstructure led to the homogeneous precipitation of γ′ and γ″ strengthening phases with δ and brittle Laves phases in grain boundaries. The average grain size of 41.56 µm in AF samples was increased to 44.80 µm after SAHT. The reduction of dislocation movements resulted in converting low angle grain boundaries found in the AF sample to high angle grain boundaries. SAHT samples displayed cubical texture along the <100> and <010> directions in the (001) plane. Following SAHT, there were increases in yield and ultimate tensile strength of 26.44% and 44.74%, respectively. On the other hand, the degree of elongation decreased to 36.19%. TRS in AF samples was converted into compressive surface residual stress following SAHT due to the phase transition. The process–structure–property relationship and the impacts of SAHT on the mechanical characteristics of the IN718 produced by L-PBF have been improved upon through this study.