Multiscale simulation and experimental optimization of process parameters and post-treatment for laser powder bed fusion of high-strength Ni-based superalloy

High-strength Ni-based superalloys encounter challenges in forming quality and mechanical properties when manufactured using laser powder bed fusion (LPBF). This research reveals the link among process, microstructure, and property of DD98M alloy through multiscale simulation as well as experimental optimization. Excessive or inadequate scanning speed and laser power lead to uneven track and poor forming quality, the integration of scanning speed 700mm/s and laser power 120W that exhibits conduction-mode and stable molten pool is chosen. The solidified microstructure is predicted to transform from coarser columnar structure to finer equiaxed structure from molten pool bottom to its top, the driving force for boundary movement of oriented grain relies on the potential of grain boundary. Moreover, the manufacturing quality of DD98M alloy is verified and further improved by changing scanning strategy and applying hot isostatic pressing. B-scan produces the {001}<100> cube texture, but the recrystallization and weakened texture are obvious in B-scan+90°/67° specimens. The high yield strength of B-scan+90°/67° specimens is mostly ascribed to solid solution and dislocation strengthening, some large and deep primary dimples on fracture surfaces represent ductile fracture. The proper heat treatment promotes the production and uniform distribution of primary, secondary and tertiary γ' phases, thus the yield strength and ultimate tensile strength of DD98M alloy are greatly enhanced. The combination of mesoscopic-microscopic simulation and experiment accelerates the research from process to microstructure and property of LPBF-processed superalloy.