With recent technological advances in additive manufacturing, laser-directed energy deposition (L-DED) is frequently chosen as a manufacturing process of Inconel 718 (IN718), which is a precipitation hardening alloy that exhibits excellent mechanical properties at elevated temperature after various heat treatments. However, undesirable recrystallization occurs during the post-heat treatment, resulting in the growth of equiaxed grains, which offset the advantage of columnar grain structure from the layer-by-layer deposition. Induction heating-assisted L-DED, which uses induction heating during the deposition, has the potential to skip the first step of the heat treatment by maintaining the deposit temperature at the heat treatment temperature. In this study, three cube-shaped IN718 were deposited using the induction heating-assisted L-DED system at the holding temperature of homogenization, solution, aging heat treatment, respectively. The temperature conditions were selected according to the standard heat treatment specification of IN718 product. In the induction heating-assisted L-DED, microstructure of the deposits strongly depends on the holding temperature of induction heating during deposition. For each deposit, the secondary phases were analyzed by using a scanning electron microscope and the grain structures were studied using electron backscattered diffraction. Additionally, the mechanical properties of each deposit were evaluated. The results of this study can provide the guide for selecting the proper holding temperature during the induction heating-assisted L-DED to achieve the desired microstructure and mechanical properties.
Keywords
- Induction Heating
- Laser-Directed Energy Deposition
- Nickel-Based Superalloy