Ni-based superalloys are widely used in aerospace and energy sectors due to their exceptional mechanical properties and ability to withstand high temperatures. The performance of these alloys is strongly influenced by their microstructural evolution during solidification and heat treatment processes, particularly during precipitation heat treatment. This study uses phase-field simulations coupled with CALPHAD-based thermodynamic and kinetic databases to model the microstructural evolution of Ni-based superalloys. The phase-field approach provides a deeper understanding of fundamental mechanisms such as nucleation, growth kinetics, and solute diffusion, capturing the key physical processes active at the microscopic scale. The first part of this study focuses on CMSX-4, a single-crystal Ni-based superalloy, to simulate dendritic growth, solute redistribution, and elemental segregation under rapid solidification conditions characteristic of Electron Beam Additive Manufacturing (EBAM). These simulations provide critical insights into the rapid solidification process, particularly the morphology and scale of the resulting microstructure [1,2]. In the second part, the analysis is extended to investigate the effects of process parameters on microstructure evolution in Alloy 718 (e.g. from Inconel) fabricated via Laser Powder Bed Fusion (LPBF). A phase-field model-based workflow is employed to simulate various heat treatment strategies, beginning with the as-built microstructure, which consists of eutectic Laves phases and a solid solution γ matrix. The study first examines how the initial LPBF-produced microstructure and subsequent homogenization treatments influence the elemental distribution of alloying elements in Alloy 718 [3]. It then assesses the impact of different heat treatment strategies on the formation, volume fraction, and spatial distribution of γ′, γ″, and δ precipitates. The simulation results are validated against experimental data obtained from the same material, confirming the reliability and predictive accuracy of the modelling framework. REFERENCES [1] Steinbach, I., Uddagiri, M., Salama, H., Ali, M. A., & Shchyglo, O. (2024). Highly complex materials processes as understood by phase-field simulations: Additive manufacturing, bainitic transformation in steel and high-temperature creep of superalloys. MRS Bulletin, 49(6), 583-593. [2] Uddagiri, M., Shchyglo, O., Steinbach, I., & Tegeler, M. (2024). Solidification of the Ni-based superalloy