Modeling of hydrogen thermal desorption profile of pure iron and eutectoid steel

Ebihara, Kenichi   ; Suzudo, Tomoaki   ; Kaburaki, Hideo; Takai, Kenichi*; Takebayashi, Shigeto*

In thermal desorption analysis(TDA), a hydrogen desorption profile, which represents the relation between the amount of desorbed hydrogen and specimen temperature, can be obtained by heating the specimen including hydrogen with a certain rate. We can estimate the amount of sites trapping hydrogen in the specimen, such as vacancies, dislocations and interfaces of phases from the profile. We have developed a numerical model to simulate the hydrogen desorption profiles for pure iron and eutectoid steel. Our model incorporates the equation of McNabb and Foster, which is a kind of rate equation, without the hydrogen diffusion term combined with the Oriani's local equilibrium theory, which describes the hydrogen trapping state. It is found that the present numerical model successfully simulates the profile both for pure iron and for eutectoid steel. We further verify the model by discussing the trapping site concentration and the effect of hydrogen diffusion.