Correlation between grain boundary misorientation and M₂₃C ₆ precipitation behaviors in a wrought Ni-based superalloy

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 M ₂₃C₆ 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.