Understanding Annealing Behavior During Post-Built Heat Treatment of Ni-Based Alloys Across Additive Manufacturing Processes

Ni-based alloys are used for high temperature structural components that span from small, highly complex, with fine feature resolution to large, simple shapes with low dimensional tolerances, necessitating the use of processes spanning from laser powder bed fusion (LPBF) to wire arc additive manufacturing (WAAM). However, there is very little understanding about how annealing behavior during post-build heat treatments varies between additive manufacturing processes. In this work, we explore the annealing behavior of IN625 and Haynes 282, manufactured with WAAM and LPBF, under the same annealing conditions. The results of hardness measurements after annealing indicate that for both IN625 and Haynes 282, the LPBF samples show larger decreases in hardness between the as-built condition and after annealing at 1200 °C for 1 h compared to the WAAM samples. LPBF IN625 and Haynes 282 samples annealed at 1200 °C for 1 h, all show complete and partial recrystallization, respectively, whereas none of the WAAM samples annealed at this temperature show recrystallization. For a given alloy, both LPBF and WAAM samples annealed at 1200 °C show particles with compositions consistent with MC carbides that are predicted from thermodynamic simulations. The MC particles present are of similar size and distribution in both LPBF and WAAM samples indicating a similar capacity for these particles to pin moving boundaries during recrystallization. In concert, these results suggest that LPBF samples have more stored energy in the as-built condition compared to their WAAM counterparts, and therefore have a higher driving force for recovery and recrystallization.