Effect of grain boundary and V carbide interface character on hydrogen embrittlement of steels: An atomistic simulation

Abstract

Abstract

Demanding for the use of high strength steels has been increased in the structural materials industry. However, Hydrogen embrittlement has been a serious obstacle to the use of high strength steels in structural applications for many decades. In the present study, methods to improve the hydrogen embrittlement resistance of steels are investigated by using atomistic simulation based on (semi-) empirical interatomic potentials.

Firstly, the influence of hydrogen on the crack propagation behavior on grain boundaries of bcc iron is investigated using atomistic simulations. We found that the hydrogen segregation tendency on grain boundaries was closely related to the grain boundary energy, and the influence of hydrogen on the grain boundary crack propagation was different according to the GB orientation. Various crack propagation behavior (intragnanular cleavage crack, intergranular crack along GB and plastic deformation) were observed with hydrogen segregation. An intergranular crack occurred in most GBs, while plastic deformation (dislocation emission and twinning) occurred in Σ3 coherent twin boundary (CTB). The Σ3 CTB showed retarded crack propagation due to the plastic deformation and is thought to be effective in improving the HE resistance.

Secondly, influence of the Fe/VC interface coherency on the hydrogen trap behavior is investigated using an atomistic simulation. For this purpose, the hydrogen trap tendency for coherent, semi-coherent and incoherent interfaces is analyzed. It is found that the coherent and semi-coherent interfaces strongly trap the hydrogen, while the incoherent interface traps the hydrogen weakly. Based on the difference in hydrogen trap behavior of each interface, the coherent and semi-coherent interfaces is expected to be effective in improving the hydrogen embrittlement resistance of steels.

These work provides a mechanistic framework for guiding the microstructure design of steels for improved resistance of hydrogen embrittlement.