Effect of treatment mode on microstructure evolution and mechanical properties of nickel-based superalloy fabricated by selective laser melting

Combined with scanning electron microscopy, transmission electron microscope, X-ray diffraction and electron backscatter diffraction, the effects of three treatment modes consisting of as-deposited, solid solution and solution aging state on mechanical structure-properties of a nickel-based superalloy fabricated by selective laser melting were studied. Grains have preferred orientation, i.e. strong texture along {100}. The phase transformation processes during post-heat treatments include dissolution of Laves phase, precipitation of strengthening phases γ′, γ′′ and δ, and size reduction of δ phase. Especially for solution aging treatment, the refined grains, high dislocation density and added high-angle grain boundaries cause a significant increase in strength and a decrease in ductility, which is consistent with the results of the tensile tests. The interior cracking behavior related to the micro-voids and microcracks formed by dislocation pile-ups and uncoordinated deformation around harder δ phase in a vacuum environment becomes a typical ductile failure mode.