TY - JOUR A1 - Fardan, Ahmed A1 - Fazi, Andrea A1 - Schröder, Jakob A1 - Mishurova, Tatiana A1 - Deckers, Tobias A1 - Bruno, Giovanni A1 - Thuvander, Matthias A1 - Markström, Andreas A1 - Brodin, Hakan A1 - Hryha, Eduard T1 - Microstructure tailoring for crack mitigation in CM247LC manufactured by powder bed fusion – Laser beam N2 - Tailored microstructures in powder bed fusion – laser beam (PBF-LB) can aid in crack mitigation of non-weldable Ni-base superalloys such as CM247LC. This study explores the effect of a range of stripe widths from 5 mm down to 0.2 mm to control solidification cracking, microstructure, and residual stress in CM247LC manufactured by PBF-LB. The decrease in melt pool depth with the reduction in stripe width from 5 to 0.2 mm promoted the < 100 > crystallographic texture along the build direction. The crack density measurements indicated that there is an increase from 0.62 mm/mm2 (5 mm) to 1.71 mm/mm2 (1 mm) followed by a decrease to 0.33 mm/mm2 (0.2 mm). Atom probe tomography investigations at high-angle grain boundaries revealed that there is higher Hf segregation in 0.2 mm stripe width when compared to 5 mm. This indicates that the cracking behavior is likely influenced by the grain boundary segregation which in turn is dependent on melt pool shape/size and mushy zone length indicated by accompanying simulations. Residual stress, measured by X-ray diffraction, decreased from 842 MPa (5 mm) to 690 MPa (1 mm), followed by an abnormal rise to 842 MPa (0.7 mm) and 875 MPa (0.5 mm). This residual stress behavior is likely associated with the cracks acting as a stress relief mechanism. However, the 0.2 mm stripe width exhibited the lowest stress of 647 MPa, suggesting a different mechanism for stress relief, possibly due to re-melting. These findings highlight the critical role of stripe width as a scan strategy in PBF-LB processing of crack-susceptible alloys. KW - Additive manufacturing KW - Residual stress KW - Scanning strategy KW - Non-weldable superalloy KW - Solidification cracking PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624606 DO - https://doi.org/10.1016/j.addma.2025.104672 SN - 2214-7810 VL - 99 SP - 1 EP - 14 PB - Elsevier B.V. AN - OPUS4-62460 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fardan, Ahmed A1 - Fazi, Andrea A1 - Peng, Ru Lin A1 - Mishurova, Tatiana A1 - Thuvander, Mattias A1 - Bruno, Giovanni A1 - Brodin, Håkan A1 - Hryha, Eduard T1 - Fine-Tuning Melt Pools and Microstructures: Taming Cracks in Powder Bed Fusion—Laser Beam of a non-weldable Ni-base Superalloy N2 - Powder Bed Fusion – Laser Beam (PBF-LB) of high γ’ strengthened Ni-base superalloys, such as CM247LC, is of great interest for high temperature applications in gas turbines. However, PBF-LB of CM247LC is challenging due to the high cracking susceptibility during PBF-LB processing (solidification cracking) and heat treatment (strain age cracking, mostly caused by residual stresses). This study focuses on understanding the impact of process parameters on microstructure, residual stresses and solidification cracking. Laser power (P), speed (v) and hatch spacing (h) were varied while the layer thickness (t) was fixed. The melt pool size and shape were found to be key factors in minimizing solidification cracking. Narrower and shallower melt pools, achieved using a low line energy density (LED = P/v ≤ 0.1 J/mm), gave low crack densities (0.7 mm/mm2). A tight hatch spacing (h = 0.03 mm) resulted in reduced lack of fusion porosity. Electron backscatter diffraction investigations revealed that parameters giving finer microstructure with 〈100〉crystallographic texture had low crack densities provided they were processed with a low LED. Atom probe tomography elucidated early stages of spinodal decomposition in the as-built condition, where Cr and Al cluster separately. The extent of spinodal decomposition was found to be affected by the LED and the hatch spacing. Samples with low LED and small hatch spacing showed higher degrees of spinodal decomposition. X-ray diffraction residual stress investigations revealed that the residual stress is proportional to the volumetric energy density (VED = P/(v. h. t)). Although low residual stresses can be achieved by using low VED, there is a high risk of lack of fusion. Hence, other parameters such as modified scan strategy, build plate pre-heating and pulsed laser mode, must be further explored to minimize the residual stresses to reduce the strain age cracking susceptibility. KW - Additive manufacturing KW - X-ray CT KW - Non-weldable superalloy KW - Solidification cracking PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597340 DO - https://doi.org/10.1016/j.mtla.2024.102059 SN - 2589-1529 VL - 34 IS - 102059 SP - 1 EP - 16 PB - Elsevier B.V. AN - OPUS4-59734 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -