Effects of applied cathodic current density, strain rate and tempering temperature on the susceptibility to hydrogen embrittlement(HE) of HY-130 steel were measured at constant strain rates in a acidified synthetic sea water containing 0.1 N $H_2SO_4$ + 1 g/L Thiourea as a hydrogen poison, and influences of these parameters on the fracture modes of the alloy were discussed by proposing schematic fracture mechanism maps.
With an increase in the cathodic current density, the response to HE of the alloy exhibits significant different behaviors when evaluated in terms of the fracture modes and the strain to failure ratio. The results could be divided into three regions. In region I obtained at low cathodic current density, the alloy was immune to HE and fractured in the ductile fracture mode. In region II, the susceptibility to HE increased significantly with cathodic current density where fracture occurred in a mixed mode of tearing(Mode III) and brittle intergranular fracture with macro-deformation(Mode II BIF). In contrast to this, in region III achieved at high cathodic current density, the alloy is very sensitive to HE with the strain to failure ratio remained at very low values and fractured by a brittle intergranular fracture mode(Mode I BIF).
The effects of strain rate or tempering temperature as a function of cathodic current density on the response to HE of HY-130 steel were presented by schematic fracture mechanism maps. With decreasing the strain rate, the region for the mixed mode of Mode II BIF and Mode III increased at the expense of the region for ductile fracture mode, with the region for Mode I BIF unaffected. With increasing the tempering temperature from 550℃ to 650℃, the region for the mixed mode of Mode II BIF and Mode III was expanded at the expense of the region for ductile fracture mode, with the region for the Mode I BIF increased at the expense of the region for the mixed mode.
