Nanosize boride particles in heat-treated nickel base superalloys

Grain boundary microconstituents in aged nickel-based superalloys were studied by transmission electron microscopy techniques. A nanosized M5B3 boride phase, possibly formed by intergranular solute desegregation-induced precipitation, was positively identified. The presence of these intergranular nanoborides provides reasonable clarification of a previously reported reduction of grain boundary liquation temperature during the weld heat affected zone thermal cycle.