Hydrogen assisted cracking of high-strength weldable steels in sea-water

Hydrogen degradation of high-strength steels and their welded joints has been evaluated under various load modes in sea-water. Slow-strain rate tensile test (SSRT), and low-cycle fatigue test were carried out in sea-water under cathodic polarisation. Two steel grades with minimum yield strength of 690 MPa, and theirs submerged arc welded (SAW) and shielded metal arc welded (SMAW) joints were examined. For SSRT the applied strain rate was 10−6 s−1. Relative values of: fracture energy, elongation, reduction in area and tensile strength were chosen as measures of hydrogen degradation. For fatigue test uniaxial tension loading under strain control (R = 0, Δɛ = 0.2–8%) was carried out at frequency 0.1 s−1. Reduction of time to failure was a measure of hydrogen degradation. Fracture modes were investigated with the use of a scanning electron microscope (SEM).