Combined thermal desorption spectroscopy, differential scanning calorimetry, scanning electron microscopy and X-ray diffraction study of hydrogen trapping in cold deformed TRIP steel

Thermal desorption spectroscopy (TDS) is a very important tool when evaluating hydrogen-material interactions. It allows a distinction to be drawn between different hydrogen traps in the material based on determination of the peak temperatures for hydrogen desorption during heating. These temperatures depend on the metallurgical and microstructural characteristics of the material and provide important information on the possible mechanisms of hydrogen embrittlement. In the present work TDS experiments were performed on a transformation-induced plasticity (TRIP) steel and combined with an in-depth characterization of the microstructure by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The TRIP steel was subjected to different degrees of cold deformation in order to correlate the changing microstructure with the TDS peaks. In order to improve our understanding the results obtained for the TRIP grade steel were also compared with those obtained for electrolytically pure iron, which contained only a limited amount of possible trap sites. Here as well, an increasing number of defects were introduced by cold deformation. Significant differences between the two materials and a significant impact of the degree of cold deformation were observed for TRIP steels, allowing a correlation between the TDS peaks and specific microstructural features. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.