Effect of serrated grain boundaries on the creep property of Inconel 718 superalloy

This article presents an investigation of the effect of serrated grain boundaries on the high temperature creep behaviour of IN718 superalloy. XRD, DSC, SEM and TEM have been conducted to study the microstructures; experimental results have shown that the morphology of grain boundaries can be a function of heat treatment conditions. In addition, creep tests have been performed on samples with and without serrated grain boundaries under 650 °C/625 MPa. In conclusions, the formation of δ phase during the heat treatment can influence the morphology of grain boundaries, and an improvement of 400 h creep rupture life has been attributed to the serrated grain boundaries.

► Modification in heat treatment process can result in the formation of serrated grain boundaries.
► Serrated grain boundaries do not affect the primary and secondary creep behaviours.
► Serrated grain boundaries can lower the creep strain rate in the tertiary creep region.
► Serrated grain boundaries can prolong the creep rupture life significantly.