Examining Solidification in Solid-Solution Ni-Based Superalloys Processed by Laser Powder Bed Fusion

Ni-based superalloys are well known for their exceptional performance in demanding environments characterized by high temperatures, corrosive conditions, or exposure to energetic particles. Among these, solid solution strengthened (SSS) superalloys, such as Inconel (IN) 625, have been meticulously engineered to exist as a single-phase, ensuring exceptional thermal stability under extreme conditions while offering superior corrosion resistance compared to its γ’/γ” strengthened counterparts. The emergence of laser powder bed fusion (LPBF) additive manufacturing has revolutionized the landscape of superalloy fabrication. LPBF has demonstrated the fabrication of intricate components with near-theoretical density and the achievement of near-net shapes, offering unprecedented flexibility and efficiency in manufacturing processes. Despite the immense promise LPBF holds for superalloy fabrication, the majority of research efforts have been concentrated on IN625 and γ’-forming alloys like IN718 or 282. However, recent studies have extended their focus to include the optimization of processing parameters and material properties of other SSS alloys, such as Hastelloy X or Ni-230, to minimize or eliminate cracking behavior. This study contributes to this expanding field by investigating three different SSS alloys—IN625, IN617, and Ni230—processed under identical LPBF conditions. Employing a design of experiments methodology, the study systematically maps the evolution of defects across the three alloy systems. Initial findings reveal distinct differences in defect formation tendencies, highlighting the nuanced interplay between alloy composition and processing strategy. To deepen the understanding of solidification mechanisms, kinetics, and phase transformations, the study employs calculation of phase diagrams (CALPHAD) modeling. This computational approach elucidates the underlying processes governing microstructural evolution during LPBF. Supporting the CALPHAD modeling, electron microscopy is utilized to identify and confirm the formation of any secondary phases. Additionally, the study explores the tensile mechanical properties of the fabricated components, providing comprehensive insights into the performance of SSS alloys manufactured via LPBF.