Hydrogen thermal desorption relevant to delayed-fracture susceptibility ofhigh-strength steels

The susceptibility to hydrogen embrittlement (HE) of martensitic steels has been examined by means of a delayed-fracture test and hydrogen thermal des orption analysis. The intensity of a desorption-rate peak around 50 degrees C to 200 degreesC increased when the specimen was preloaded and more remark ably so when it was loaded under the presence of hydrogen. The increment ap peared initially at the low-temperature region in the original peak. As hyd rogen entry proceeded, the increment then appeared at the high-temperature region, while that in the low-temperature region was reduced. The alteratio n occurred earlier in steels tempered at lower temperatures, with a higher embrittlement susceptibility. A defect acting as the trap of the desorption in the high-temperature region was assigned to large vacancy clusters that have higher binding energies with hydrogen. Deformation-induced generation of vacancies and their clustering have been considered to be promoted by h ydrogen and to play a primary role on the HE susceptibility of high-strengt h steel.