IN939 is a precipitation-hardenable Ni-base superalloy. It has been widely used for blades and vanes in gas turbines, and aircraft engines due to its outstanding properties such as high microstructural stability up to 850 oC, high corrosion, oxidation and creep resistance. Recently, a growing interest in the fabrication of IN939 parts with the PBF-LB process has emerged due to its significant advantages such as intricate geometric complexity in a single step, design freedom, as well as reductions in material waste and tooling costs. IN939 is considered reasonably weldable yet it is crack-susceptible. There is a significant gap in the literature concerning the influence of PBF-LB process parameters and subsequent heat treatments on the material characteristics of IN939 compared to established Ni-base superalloys like IN718 and IN625. For this reason, investigation of the effects of PBF-LB process parameters and post-heat treatment on the material properties of IN939 is crucial to obtain crack- and defect-free components. This thesis investigates the effects of PBF-LB process parameters and post-heat treatments on IN939. Through a systematic approach, the research evaluates the characteristics of IN939 powders, including virgin and spatter powders, and their impact on part quality and process efficiency. Furthermore, the influence of PBF-LB process parameters such as laser power, scanning speed, and hatch distance on material properties is comprehensively analyzed, emphasizing parameter optimization for defect mitigation and surface quality improvement. Additionally, the investigation delves into the effects of different scanning strategies on the material properties of IN939, providing valuable insights into optimizing scanning parameters to achieve desired performance. Moreover, this study explores the impact of various solution heat treatment temperatures on the material properties of IN718 and IN939, offering practical recommendations for heat treatment parameter optimization.