Computer simulation of intergranular stress corrosion cracking via hydrogen embrittlement

Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlem ent mechanism. The simulation employs computational modules that address (a ) transport and reactions of aqueous species giving rise to hydrogen genera tion at the liquid-metal interface, (b) solid-state transport of hydrogen v ia intergranular and transgranular diffusion pathways and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the deve lopment of the computational model has been the role of materials microstru cture (precipitate particles and grain boundaries) on hydrogen transport an d embrittlement. Simulation results reveal that intergranular fracture is e nhanced as grain boundaries are weakened and that microstructures with grai ns elongated perpendicular to the stress axis are more susceptible to crack ing. The presence of intergranular precipitates may be expected to either e nhance or impede cracking, depending on the relative distribution of hydrog en between the grain boundaries and the precipitate-matrix interfaces. Calc ulations of hydrogen outgassing and ingassing demonstrate the strong effect of the charging method on the fracture behaviour.