Brittle intergranular fracture of a Ni-base superalloy at high temperatures by dynamic embrittlement

Oxygen-induced dynamic embrittlement of nickel (Ni)-base superalloys at 650 °C has been studied by static loading of notched bars in pure bending at fixed displacement on IN718 in the form of conventionally heat-treated polycrystals, polycrystals specially processed to increase the fraction of Σ3 boundaries, and bicrystals with a random high-angle boundary and a Σ5 tilt boundaries. The susceptibility to cracking is shown to depend strongly on grain-boundary character.