The influence of the melt pool structure on the mechanical properties of laser powder bed fusion Nickel Superalloy 625

Qualification of additive manufacturing (AM) parts requires exploring the process-structure-property relationships for a large number of process variables and unique macro/microstructure features associated with AM processes. This investigation explores the unique melt pool structure influences on a Nickel superalloy 625. Samples were built with different laser parameters and build orientations. They were then systematically characterized, including the macrostructure down to the microstructure sub-micrometer dendrites. Mechanical characterization was performed through tensile testing, microhardness, strain hardening behavior, and fracture analysis. The significance of the melt pool structure was shown to directly affect properties. The elongation of the parts was dependent on the continuity of the track segments, with easier crack propagation paths appearing in samples with more whole segment traces in the fracture (especially in Z samples). Interactions between built layers and tensile direction were also observed. The investigation elucidates properties and features that are process-related (independent of the material system), which can carry over to other material systems fabricated with additive manufacturing. The investigation also highlights ways that process-related and material-related properties and features interact.