Analysis of Grain Boundary Character in a Fine-Grained Nickel-Based Superalloy 718

摘要

In the current work, sheets of superalloy 718 were processed via thermomechanical route by hot and cold rolling, followed by annealing below the delta phase solvus temperature and precipitation hardening to optimum strength. Grain boundary character distribution throughout the processing was mapped via EBSD and its evolution discussed. The results show that it is possible to process the alloy to a fine grain size obtaining concomitantly a considerably high proportion of special boundaries Sigma 3, Sigma 9, and Sigma 27. The precipitation of delta phase presented a strong grain refining role, without significantly impairing the twinning mechanism and, consequently, the Sigma 3, Sigma 9, and Sigma 27 boundary formations.