Laves phase control of inconel 718 superalloy fabricated by laser direct energy deposition via δ aging and solution treatment

In order to achieve the microstructure homogeneity at a lower temperature and improve the mechanical properties, a novel post heat treatment was introduced to Inconel 718 fabricated by laser direct energy deposition (LDED), by means of delta aging treatment + solution treatment. The microstructure analysis shows that the fully precipitation of delta phase in LDED Inconel 718 superalloy can "cut" the long strip Laves phase into small pieces. According with the delta phase solution treated at 1020 degrees C for 30 min, only tiny particle Laves phase was remained. The equilibrium volume fraction of Laves phase after delta phase solution treatment is about 1%, which is much lower than that of the as-deposited sample or the sample only solution treated at 1020 C. Due to the solution strengthening and precipitation of gamma '' phase during aging treatment, the tensile strength of delta aging + delta solution + double aging treated samples was 10.27% higher than that of directed solution + double aging treated samples, as well as a 31.38% and 52.71% increases in elongation and the reduction of area during tensile tests. (C) 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).