Role of heat treatment in enhancing microstructure and properties of Inconel 625 manufactured by directed energy deposition using wire arc

Abstract

Inconel 625, a nickel-based superalloy, is known for its exceptional mechanical properties and corrosion resistance, widely utilized in aerospace, marine, and chemical industries. Inconel 625 components fabricated by Directed Energy Deposition using Wire Arc (DED-Wire Arc), exhibit coarse dendritic microstructures and Laves phases in the as-built state, necessitating heat treatments for property enhancement. Heat treatments at 1050–1100 °C improved tensile strength by up to 15–17 % (e.g., from 850 MPa to 980 MPa for DED-Arc) and hardness by 40–52 % (e.g., from 250 HV to 380 HV). Solubilisation effectively dissolved Laves and MC-type carbides, reducing phase fractions to 15 % and promoting a more uniform microstructure. Annealing at 700–900 °C induced γ′ and γ′′ precipitates, optimizing hardness while maintaining elongation. Comparatively, DED-LB and PBF-LB techniques, with finer as-built microstructures, achieved better responses to heat treatments, reaching tensile strengths of 1050 MPa and elongations of 25 % post-solubilisation. Rapid quenching methods controlled recrystallization, reducing grain boundaries and improving corrosion resistance by 32 % in corrosion potential and decreasing passivation current density by 52 %. This study highlights the significant role of heat treatments in enhancing the microstructure and properties of Inconel 625 produced by DED-Wire Arc, positioning it as a reliable candidate for demanding industrial applications.