Hydrogen degradation of high-strength weldable steels in seawater

Hydrogen degradation of high-strength weldable steels was evaluated under monotonic static tensile loading in seawater at room temperature. Two types of quenched and tempered steels and their submerged-arc welded and shielded-metal-arc welded joints were examined. The slow-strain-rate tests were carried out on cylindrical smooth specimens in air and in artificial seawater. The tests in seawater were. performed under cathodic polarization for various current densities. The relative values of fracture energy, time to failure, elongation, reduction in area, and tensile strength were used as measures of hydrogen degradation. The permeation of hydrogen through the base metal, the heat-affected zone, and the weld metal were analyzed by using the conventional Devanathan-Stachurski method. The hydrogen diffusivity and the content of diffusible hydrogen were established. The observed decrease in the relative values of the degradation parameters with the increase in the current density exhibits a certain minimum. The loss of plasticity was as high as 70-90% for the base metals and welded joints. The subsequent increase in the current density does not cause higher degradation. Good correlation was obtained between the relative parameters of degradation (except tensile strength) and the concentration of diffusible hydrogen.