Influence of charged hydrogen on tensile behavior of a pressure vessel steel at relatively high temperatures

The influence of hydrogen charged cathodically on the tensile behavior of pressure vessel steel SA508 C1.3 has been investigated in the temperature range 200 - 350 degreesC. It was found that the charged hydrogen induced a marked softening and a decrease in ductility at these temperatures, especially in the dynamic strain aging (DSA) region. Correspondingly, some flat or brittle-like areas appeared on the fracture surfaces locally and the dimples became smaller and shallower. Moreover, the presence of hydrogen moved the critical temperature at which DSA takes place to a higher temperature. The possible interactions between hydrogen and DSA at relatively high temperatures and the related mechanisms are also discussed according to the above experimental results.