Thermal desorption spectroscopy study of the interaction of hydrogen with TiC precipitates

Thermal desorption spectroscopy (TDS) was used to study hydrogen-trap interactions for an experimental steel (0.025 wt%C-0.09%Ti). After lab processing, the microstructure consisted of small (similar to 20 mu m) ferrite grains containing nanometer TiC precipitates. After hot and cold rolling, the material contained some hydrogen (originated from the hot rolling) in irreversible traps, the TiC precipitates. After annealing in hydrogen, the TDS spectra consisted of a high temperature peak, attributed to irreversible trapping by TiC precipitates. Annealing slightly increased the TiC precipitate size. Both the peak temperature and peak area increased with increasing annealing temperature. The increase in peak area occurred together with the increase in TiC precipitate size. The TDS spectra for samples annealed at 800 A degrees C, and electrochemically charged, contained (i) a low temperature peak which decreased in height with increasing desorption time, and (ii) a high temperature peak that did not change significantly with desorption time, and was similar to those after gaseous charging. The low temperature peak was attributed to reversible traps such as grain boundaries, whereas the high temperature peak was attributed to irreversible trapping by TiC precipitates. The high temperature TDS peak was composed of constituent peaks with essentially the same activation energy of 145 kJ/mol.