Assessment of the susceptibility to hydrogen embrittlement. II: Effect of specimen geometry on delayed failure time of 38 NiCrMo 4 steel

Delayed failure tests, in which suitable samples were cathodically charged with hydrogen (current density 8 mA·cm^?2) in 0.1N sulphuric acid, while under sustained tensile loads, were carried out on a low alloyed Ni-Cr steel (UNI 38 NiCrMo 4). The effect of the geometry on the delayed failure time was assessed using specimens with different diameters (2,3,4 mm) and different lengths (13, 23, 33 mm). The experimental results showed that the specimen geometry does not influence the material behaviour: only a minor effect on the threshold stress value was noted due to diameter variations.