Homogenization and Solution Annealing Heat Treatments of Powder Bed Fused Inconel 718

The recent development of metal additive manufacturing provides a new approach to fabricating complex IN718 parts with minimal machining. However, additively manufactured IN718 parts suffer from anisotropic mechanical properties, and are usually inferior to conventionally produced parts. This is especially noticeable under dynamic loading conditions, where they suffer from lower fatigue strength and life, as well as lower reliability. This study focuses on post-processing heat treatments that aim to homogenize the microstructure of the additively manufactured IN718. Modified solution annealing treatments were proposed for IN718 samples, which were subsequently tensile tested. The microstructure of the treated specimens was then characterized using x-ray diffraction and scanning electron microscopy imaging. The results showed that increasing the initial heat treatment temperature enhanced the isotropy, Young’s modulus, and ductility, at the expense of a slight reduction in the tensile strength. The further rise in the heat treatment temperature significantly increased the grain size and produced unfavorable precipitate morphology, which caused a brittle behavior. The work finally exhibits a modified heat treatment process for the additively manufactured IN718 material that successfully enhances its mechanical properties.