Misorientation dependence of grain boundary migration in advanced ultra-supercritical Ni-based superalloy

ABSTRACTThe microstructures of a Ni-based superalloy used in the advanced ultra-supercritical condition were investigated after creep deformation. The grain boundary migrated during tertiary creep. Accompanied by the migration of grain boundaries, the coarsened γ′ phase with rodlike shape was formed and the precipitate-free zones emerged around this coarsened γ′. The distributional misorientation angle of these grain boundaries was from 45° to 65°. After the examination of the distribution characteristics of the cracks, it was found that the intergranular cracks did not propagate through the precipitate-free zones with the coarsened γ′.