Comprehensive optimization of tensile and creep properties of Inconel 718 superalloy at room temperature and elevated temperature through grain boundary engineering treatments

As the most widely used commercial Ni-based superalloy, the process of Inconel 718 superalloy is designed with the goal of achieving superior mechanical properties. The grain boundary engineering (GBE) as a thermomechanical processing strategy, can be used to optimize mechanical properties by enhancing low coincident site lattice (CSL) grain boundaries. In this paper, we improve the tensile and creep properties of Inconel 718 superalloy at room temperature and elevated temperature by GBE treatment. Dislocations show a higher tendency to transfer across CSL grain boundaries with higher geometric compatibility parameters rather than random grain boundaries. The high fraction of CSL grain boundaries can reduce stress concentration by inhibiting the pile-ups of dislocation along the grain boundary and then optimizes the tensile properties at room temperature and elevated temperature. Moreover, the high fraction of ∑3 CSL grain boundaries contributes to the formation of twins during creep loading, resulting in an improvement in creep performance. This work is expected to provide valuable insights for enhancing the comprehensive mechanical properties of Inconel 718 and similar Ni-based superalloys.