Tuning microstructure and mechanical properties of SLM-processed GH5188 cobalt superalloy via annealing treatment
摘要
Annealing is essential for mitigating defects in selective laser melting (SLM)-fabricated GH5188 superalloy intended for industrial applications. A clear understanding of the temperature-dependent microstructural evolution remains critical for performance optimization. This study systematically investigates the influence of annealing temperature (650–1200 °C) on the microstructure and mechanical properties of SLM-produced GH5188. Annealing at 750 °C for 1 h promotes the simultaneous formation of nanoscale M23C6 carbides along cellular substructures, combining cellular refinement with precipitation hardening to achieve a peak yield strength of ~ 764 MPa while maintaining ~ 43% uniform elongation. At intermediate temperatures (950–1150 °C), deleterious phase transformations occur, specifically the conversion of M23C6 to M6C carbides at grain boundaries, resulting in brittle fracture and degraded strength and ductility. The yield strength decreases to 654–694 MPa, and uniform elongation is reduced to 30–37%. Complete dissolution of carbides and substructures at 1200 °C eliminates all precipitates, restoring ductility to ~ 65% uniform elongation, albeit at a significantly reduced yield strength of ~ 540 MPa. These microstructural transitions, governed by carbide evolution and substructure stability, identify 750 °C as the optimal annealing condition for high-strength aerospace components, while 1200 °C is suitable for applications prioritizing ductility in complex geometries. This study provides actionable guidelines for the post-processing of SLM-fabricated refractory superalloys in aerospace applications. More importantly, it decouples the synergistic strengthen of cellular substructures and carbide precipitation across a wide temperature range, offering a novel microstructural design strategy specifically for additively manufactured cobalt-based superalloys.