Influence of specimen size and initial state on hydrogen thermal desorption profile; A Numerical study

Ebihara, Kenichi   ; Kaburaki, Hideo

The thermal desorption analysis (TDA) is the experimental method to identify hydrogen state, which is necessary for understanding the mechanism of hydrogen embrittlement in steels. From the thermal desorption profile obtained by TDA, the binding energy between hydrogen and defects, which is important for estimating the hydrogen state, can be calculated. Since the desorption profile is influenced by the specimen size and the initial hydrogen state before starting TDA, the understanding of their influence on the desorption profile is necessary. By simulating the desorption profile using the reaction-diffusion equations incorporating the parameters which were corrected by reproducing the experimental profile of martensitic steels, we confirmed that the profile peak becomes broad and the calculated binding energy becomes low when the size is large, and found that two desorption peaks are observed when the non-equilibrium state is used as initial state for the large-size specimen.