The effect of grain-boundary-engineering-type processing on oxygen-induced cracking of IN718

Polycrystalline Ni-base superalloys are prone to time-dependent intergranular failure when the loading temperatures exceeds about 873 K. The fracture process is then controlled by oxygen grain-boundary diffusion followed by decohesion of the respective boundaries. It is shown that this kind of cracking for IN718 at 923 K in air can be reduced significantly by successive steps of deformation and annealing, which is known as grain-boundary-engineering processing. This illustrates the importance of the grain-boundary-character distribution with regard to this mode of failure, which is known as ‘dynamic embrittlement.’