Characterization of γ′ Precipitation Kinetics in Additively Manufactured Ni-Based Superalloy ABD®-900AM

Abstract The γ ′ precipitation behavior in additively manufactured ABD ® -900AM is quantified in the temperature range of 700 K to 1200 K (427 °C to 927 °C). Data for γ ′ precipitate size distributions and median radii are reported as a function of annealing time and temperature. An empirical model predicting the median γ ′ precipitate size during post-build heat treatment is established, and effective diffusion coefficients are determined at the three studied temperatures. A strong correlation between median γ ′ precipitate size and bulk hardness is identified, revealing an optimum precipitate size of 10 to 20 nm for maximum hardness and enabling classification of the precipitation process into two stages: γ → γ + γ ′ transformation and subsequent coarsening. A time–temperature–transformation (TTT) diagram is constructed and further rationalized using CALPHAD and TC-PRISMA modeling. Notably, interconnected γ ′ morphologies are observed at early reaction times ( r < 6 nm), indicating the possible involvement of spinodal decomposition in the precipitation mechanism. The work provides comprehensive datasets for thermal stability, mechanical response, and phase evolution in ABD ® -900AM and offers insights for post-processing strategies and predictive modeling in AM Ni-based superalloys.