Correlation between grain boundary misorientation and M23C6 precipitation behaviors in a wrought Ni-based superalloy

Abstract

The correlation between the grain boundary misorientation and the precipitation behaviors of intergranular M23C6 carbides in a wrought Ni–Cr–W superalloy was investigated by using the electron backscattered diffraction (EBSD) technique. It was observed that the grain boundaries with a misorientation angle less than 20°, as well as all coincidence site lattice (CSL) boundaries, are immune to precipitation of the M23C6 carbides; in contrast, the random high-angle grain boundaries with a misorientation angle of 20°–40° provide preferential precipitation sites of the M23C6 carbides at the random high-angle grain boundaries with a higher misorientation angle of 55°–60°/[2 2 3] turn to retard precipitation of M23C6 carbides owing to their nature like the Σ3 grain boundaries and retard the precipitation of M23C6 carbides. The low-angle and certain random grain boundary segments induced by twins were found to interrupt the precipitation of the M23C6 carbides along the high-angle grain boundaries.