Creep Properties of Nickel Alloys - Comparison Between Conventional and Laser Powder Bed Fusion Manufacturing Routes

Abstract

Abstract PBF-LB/M (Metal Laser Powder Bed Fusion) is a commonly used additive manufacturing process for gas turbine parts. This manufacturing method allows for small quantity batches with complex part designs. The mechanical behavior of PBF-LB/M components is strongly influenced by manufacturing process parameters, such as component geometry, build orientation and post-processing steps. However, these complex correlations are not completely understood — especially not for high temperature applications. The number of publicly available publications on creep properties of nickel-based alloys is limited. This knowledge gap affects the design and qualification effort of PBF-LB/M gas turbine components. This study compares the creep properties of conventionally and additively manufactured IN738LC and IN718. The assessment of PBF-LB/M additively manufactured samples includes experimental data from two types of specimens (witness and extracted samples) in three build orientations. Extracted samples out of additively manufactured components allow the investigation of application relevant mechanical properties. Build directions studied are 0° (perpendicular to build direction), 45° (diagonal) and 90° (parallel to build direction). The results show that the creep properties of PBF-LB/M manufactured IN738LC at 850 °C are affected by build orientation. Samples oriented parallel to the build direction show favorable creep properties, especially 45° build orientations have reduced creep life properties. In comparison, the influence of build orientation is not as critical in IN718 and creep life properties at 650 °C are slightly superior to conventionally manufactured samples.