Hydrogen trapping characteristics of cold-drawn pure iron and eutectoid steel evaluated by thermal desorption spectrometry

Abstract

Hydrogen absorption characteristics of pure iron and eutectoid steel fabricated by cold drawing have been evaluated by thermal desorption spectrometry (TDS). The pure iron specimens with ferrite (α) structure and the eutectoid steel specimens with α and Fe3C structures, were produced under various degrees of reduction and also under various heat treatment conditions. These amount of hydrogen absorbed in specimens dipped in 20 mass%NH4SCN solution were measured using TDS. TDS analysis showed that hydrogen evolution rate of pure iron has only one peak, while that of eutectoid steel has two peaks. From transmission electron microscopy and TDS analysis, the lower temperature peak was attributed to hydrogen released from the trapping sites such as point defects, clustered defects, and dislocations in α. The higher temperature peak was found to correspond to hydrogen released from the trapping sites such as defects in Fe3C, and/or such as the disordered interface between α and Fe3C.