Effect of Component Geometry and Build Orientation on the Microstructure and Mechanical Properties of Nickel Superalloys Manufactured with Laser Powder Bed Fusion

Metal laser powder bed fusion (PBF-LB/M) enables high geometric design freedom. However, the resulting PBF-LB/M microstructure depends on several factors, including process parameters, part geometry, build orientation and post-processing (e.g. heat treatment) etc. The correlation between the PBF-LB/M microstructure and the influencing factors is not yet sufficiently researched or understood. Thus, there is currently a lack of transferable databases and reproducible test procedures, especially for high temperature materials. Since the geometry of components used in applications generally differs from standard witness samples, it must be investigated whether directly printed PBF-LB/M witness samples exhibit comparable material properties to samples extracted from components. Within the scope of this thesis, a generic component was designed with application-relevant geometric features, such as overhangs, changes in cross-section, etc. Witness samples were integrated within the generic component, which combined, form the Sample Extraction Component (SEC). The (witness) samples are manufactured in three build orientations: 0° (perpendicular to the build direction), 45° and 90° (parallel to the build direction). The samples extracted from the SEC are microstructurally and mechanically characterized and compared to the results of witness samples. The materials used were IN718 and IN738LC. The Ni superalloy IN738LC is challenging to process using PBF-LB/M due to its crack susceptibility. Although the mechanical properties are promising for high temperature applications, PBF-LB/M IN738LC is not yet commonly used in application. In comparison, PBF-LB/M IN718 is already used in high temperature applications. Microstructural differences regarding phase formation and distribution were found between witness and extracted samples and are attributed to the difference in solidification conditions during the PBF-LB/M process itself. The grain sizes differ, with the largest grain size found in the witness samples. The samples extracted from the SEC show smaller grains. The difference in grain sizes also causes differences in mechanical properties. The Vickers hardness of extracted samples is higher compared to witness samples. The tensile and yield strengths of the extracted samples are significantly higher than those of witness samples. The IN738LC creep properties differ from those of IN718 due to phase formation and different creep deformation mechanisms taking plac