Microstructural evolution in Electron Beam Powder Bed Fusion of a nickel-based ODS superalloy

The use of oxide dispersion strengthened (ODS) alloys in Electron Beam Powder Bed Fusion (PBF-EB, EBM) has been scarcely explored despite their potential to enhance high-temperature performance. This is primarily attributed to the inherent challenges in processing ODS materials in additive manufacturing, which are compounded by the inherent susceptibility of high-temperature alloys to cracking, as well as difficulties in achieving uniform oxide particle distribution and maintaining microstructural homogeneity. This study investigates the influence of different scan strategies on the microstructure and mechanical properties of difficult-to-weld Inconel 738LC, both with and without Y₂O₃ dispersion. The primary aim is to assess how ODS affects the material's microstructure and its performance under PBF-EB processing conditions. This work explores the effects of different scan strategies, such as line and spot melting, on microstructural features including grain size and oxide dispersion. The heat input during processing, particularly with respect to potential effects on the formation of γ' phases, is also considered. Processing challenges related to the inclusion of ODS, such as maintaining a homogeneous microstructure and minimizing defects, are discussed. Approaches to studying the behavior of nanoparticles, including potential modeling techniques, are presented. Mechanical properties such as hardness and high-temperature compressive strength are evaluated to quantify the effect of scan strategies and ODS on the alloy’s performance. The results indicate that the scan pattern has a significant influence on grain structure, anisotropy, and crack formation, while the inclusion of ODS presents challenges, particularly in terms of process stability and defect formation. This study provides insights into the role of ODS in PBF-EB and underscores the complexities associated with processing this type of materials. The findings offer a deeper understanding of how processing can be optimized to pave the way for improved high-temperature performance.