Multi-scale simulation of hydrogen influenced critical stress intensity in high Co–Ni secondary hardening steel

Highlights: • A multi-scale simulation method was used to calculate K_IC and K_ISCC value. • By atomic scale simulation, hydrogen concentration formed at the crack tip. • Stress concentration at crack tip was reduced by austenite layer. • The simulation results were consistent with the experiment results. - Abstract: Hydrogen embrittlement was an important and long-standing problem in the fields of steels, especially ultra-high strength steels. In order to simulate the ability of hydrogen embrittlement resistance for high Co–Ni secondary hardening steels, a multi-scale simulation method with four steps was used to calculate the critical stress intensity (K_IC) and hydrogen influenced critical stress intensity (K_ISCC). For the four steps: the atomic scale and nm scale simulation were mainly used to simulate the effect of stress-assisted hydrogen diffusion at the crack tip; the μm scale simulation was used to handle the effect of microstructure; the cm simulation was used to analyze the size effect. As the effect of hydrogen concentration at the crack tip, the simulation results of critical cohesive strength of the Fe(110) at the crack tip decreased by 82.3%. The μm scale simulation showed the improvement of fracture toughness with the help of austenite layer between martensite laths. Compared with the mechanical properties of 300 M and AerMet100 steels, the accuracy of this simulation method was proved.