The high-energy-density welding technologies, exemplified by processes like Electron Beam
Welding (EBW), possess the unique ability to produce exceptionally deep and narrow welds that
are defect-free. This attribute positions it as a highly reliable method for manufacturing critical
aerospace components. The precision and reliability offered by high-energy-density welding
technologies underscore their significance in ensuring the integrity and quality of vital aerospace
parts. In this study, we have endeavoured to investigate the evolution of microstructure and its
impact on the mechanical performance of additively manufactured IN718 under the influence of
pre-weld and post-weld heat treatment. Lower heat input and faster cooling rate in the EBW
process, along with circular beam oscillation, reduce Nb segregation and Laves phase in the weld
region. The effect of segregation of solute elements like (S, P, B, and Nb) along with the presence
of precipitates like NbC at grain boundary on HAZ liquation and micro-fissuring need to be
investigated to understand the operative mechanism. A set of pre-weld and post-weld heat
treatment plans is proposed to correlate tensile properties at ambient and 650°C with the
corresponding evolution of microstructure and precipitate in weld and base metal. Three solution
treatment (ST) temperatures 1180 °C 1h/AC, 1065 °C 1h/AC, and 980 °C 1h/AC are selected.
While solution heat treatment at 1180 °C 1h/AC reduced segregation, and induced
recrystallization, solution treatment at 1065 °C 1h/AC and 980 °C 1h/AC preserves columnar
texture with a reduction in segregation. Microstructure obtained shows 1065 °C 1h/AC ST avoids
δ phase formation by being above δ-solvus temperature (1010 °C), whereas 980 °C 1h/AC solution
treatment causes δ phase precipitation along the grain boundary.
Keywords: Electron Beam Welding; heat treatment; IN718; HAZ Liquation.