Observation of hydrogen distribution in high-strength steel

"The diffusible hydrogen" in Cr-Mo steels are observed with autoradiography technique. Specimens with "the diffusible hydrogen" are prepared by an ele ctrochemical cathodic charging method and those without "the diffusible hyd rogen" by annealing at 373 K after charging hydrogen. TEM autoradiographs s uggests, by the developed silver grains, that the hydrogen trapping sites a re the grain boundary and internal interface of ferrite-cementite and ferri te-lath structure. After keeping the sample at 373 K, the silver grains dis appeared. Most of hydrogen trapping sites release almost all the hydrogen a t 373 K. It is clear that these sites of high-strength steels supplies "the diffusible hydrogen". Hydrogen absorption characteristics of quench harden ing tempering Cr-Mo steels have been evaluated by thermal desorption spectr ometry (TDS). From tritium electron microscopic autoradiography and TDS ana lysis, the lower temperature (360 K-370 K) peaks show "the diffusing hydrog en" which is released a few days. "The diffusible hydrogen" from trapping s ites such as the internal interface of ferrite-cementite or ferrite-lath st ructure are distinguished to "the diffusing hydrogen." (C) 2001 Kluwer Acad emic Publishers.