Study on microstructure evolution and high-temperature mechanical properties of low cobalt GH3230 superalloy fabricated by laser powder bed fusion after post-treatment

The GH3230 alloy is a solid-solution strengthened nickel-based superalloy that finds important application in the nuclear power sector, owing to its superior high-temperature strength and corrosion resistance. However, given the limitations in service conditions and cost, a low-cobalt version of the GH3230 superalloy (with Co reduced to 0.034 wt%) was fabricated by laser powder bed fusion (LPBF) to minimize the formation of the long-lived radioactive isotope Co60 under neutron irradiation. Post-processing treatments, including hot isostatic pressing (HIP) and solution treatment (ST), were employed to mitigate the intrinsic defects from the LPBF process and enhance mechanical properties. The results indicate that the post-treatment effectively eliminates the melt pool morphology and predominantly promotes the formation of M₆C carbides. The resulting alloy achieves excellent high-temperature performance: creep life at 850 °C/78 MPa exceeds 800 h, while at 850 °C it retains a tensile strength of ∼359 MPa and elongation of ∼86%, which are comparable to those of the conventional high-cobalt counterpart (differences within ±5%). This work demonstrates the feasibility of developing high-performance, low-activation nuclear components via the LPBF process.