On the anisotropic creep behavior of a Ni-base superalloy CM247LC manufactured by powder bed fusion-laser beam

Artikel i vetenskaplig tidskrift, 2026

Additive Manufacturing (AM), specifically Powder Bed Fusion - Laser Beam (PBF-LB), offers unique capabilities for manufacturing of components with Ni-base superalloys like CM247LC, yet often introduces microstructuredependent mechanical anisotropy. This study investigates the profound influence of build direction on the high-temperature tensile creep performance and deformation mechanisms of a PBF-LB CM247LC superalloy with test conditions of 871 degrees C and 380 MPa, correlating macroscopic performance with detailed post-mortem electron backscattered diffraction and controlled electron channeling contrast imaging. Significant creep anisotropy was revealed with vertically built (VB) specimens exhibiting markedly higher creep rupture lives (100-200 h) and ductility (up to 6 %) compared to horizontally built (HB) counterparts (15 h, 0.8 %). Microstructural analysis of heat-treated specimen prior to creep confirmed the persistence of an inherent columnar grain structure, directly linking this anisotropy to the relative alignment of grains with the applied load. Post-creep microstructural analysis of ruptured vertically built specimens showed widespread plastic deformation identified through the presence of dislocations, deformation twins (microtwins) and stacking faults. In contrast, horizontal specimens show localized plastic deformation at grain boundaries, leading to premature, brittle intergranular fracture with minimal overall ductility. While the creep performance of vertically built PBF-LB CM247LC specimens approaches that of conventionally cast CM247LC, horizontally built specimens remain significantly inferior. These insights into anisotropic deformation mechanisms are crucial for optimizing design, processing, and reliable deployment of additively manufactured superalloys in high-temperature applications.