Modeling thermal desorption analysis of hydrogen in steel

A computer model was developed to simulate the thermal desorption flux of hydrogen from steel specimens by an explicit finite difference method, which is convergent and stable for all time increment. The influences of experimental parameters, e.g. ramp rate, specimen size and duration of exposure at ambient temperature etc., on the desorption spectrum, concentration profile of hydrogen in the lattice and fractional occupancy at the trapping sites, were studied assuming that the major trapping sites were dislocations. The increase in ramp rate caused a marked shift in the desorption peak to a higher temperature, whilst the increase in the specimen size shifted the peak to higher temperatures to a moderate extent. The duration of exposure may have a considerable influence on the thermal desorption spectra when the desorption peak is associated with a lower binding energy trap site.