| Abstract Scope |
The ability to manufacture complex three-dimensional (3D) components on-demand by additive manufacturing (AM) methods has become increasingly attractive for use in the nuclear industry. The technology also has the potential to raise productivity by delivering parts more rapidly than conventional fabrication methods. To make the most of these benefits, it is necessary to understand process/properties/microstructure relationships.
While several commercial studies have demonstrated the ability to fabricate Alloy 625 components by laser-powder bed fusion (L-PBF), these studies have also indicated as-built Alloy 625 is more susceptible to chemical segregation than conventional wrought material. Chemical homogenization of the as-built material can be achieved by heat treatment; however, deleterious phases can form when using heat treatments developed for wrought Alloy 625. This presentation will provide an overview of microstructure and mechanical properties of L-PBF Alloy 625 as a function of annealing temperature from 800 -1200°C (1472 - 2200°F). A range of characterization techniques were used including metallography, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy to identify microstructural features associated with optimal and sub-optimal properties. Furthermore, tradeoffs in tensile behavior and Charpy absorbed energy as a result of heat treatment are discussed in relation to the microstructural evolution observed. These studies have been performed to contribute to the current understanding of process/structure/property relationships for Alloy 625 manufactured via L-PBF methods. The fundamental knowledge gained from these studies is key to using AM-fabricated metals for demanding service conditions and/or long lifetimes. |