Computer simulation of intergranular stress corrosion cracking via hydrogen embrittlement

摘要

Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlement mechanism. The simulation employs computational modules that address (a) transport and reactions of aqueous species giving rise to hydrogen generation at the liquid-metal interface, (b) solid-state transport of hydrogen via intergranular and transgranular diffusion pathways and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the development of the computational model has been the role of materials microstructure (precipitate particles and grain boundaries) on hydrogen transport and embrittlement. Simulation results reveal that intergranular fracture is enhanced as grain boundaries are weakened and that microstructures with grains elongated perpendicular to the stress axis are more susceptible to cracking. The presence of intergranular precipitates may be expected to either enhance or impede cracking, depending on the relative distribution of hydrogen between the grain boundaries and the precipitate-matrix interfaces. Calculations of hydrogen outgassing and ingassing demonstrate the strong effect of the charging method on the fracture behaviour. [References: 28]