Numerical evaluation of the Choo and Lee's method for calculating hydrogen detrapping activation energies

Ebihara, Kenichi   ; Kaburaki, Hideo; Takai, Kenichi*

The crack causing hydrogen embrittlement is observed in steels as the structural material. Accurate evaluation of hydrogen detrapping activation energy, which represents the binding strength between hydrogen atoms and the lattice defects, is crucial to the understanding of the mechanism of hydrogen embrittlement in steels. The Choo and Lee's method, which experimentally evaluates the detrapping energy from the hydrogen thermal desorption profile, should be scrutinized, because this method neglects the hydrogen diffusion in the specimen. By their method, we have evaluated detrapping activation energies from the experimental desorption profiles for pure iron, and also from that simulated by the 1D reaction-diffusion equation. We found that their method underestimates the detrapping energies as the specimen size is large. We also found that this dependence on the specimen size is caused by the degradation of the desorption peak of the detrapping process by the diffusion process.