Interaction between hydrogen and cyclic stress and its role in fatigue damage mechanism

Abstract The interaction between hydrogen and cyclic stress were investigated on E690 steel by hydrogen pre-charging under cyclic loadings of various peak stresses, and hydrogen determination, tensile tests and observation on microstructures. Results show that hydrogen stays in E690 steel mainly in form of non-diffusion hydrogen (NDH). Peak stress exponentially increases the saturation NDH concentration through exponentially increasing the number of hydrogen trap. Different fatigue damage mechanisms were found after pre-charged for 12 h under different peak stresses (Smax) and various current densities (HCCD): (i) hydrogen-enhanced toughness (Smax ≤ 0.6 σp0.2, HCCD ≤ 25 mA∙cm−2), (ii) hydrogen embrittlement (Smax > 0.8 σp0.2, HCCD > 25 mA∙cm−2), (iii) hydrogen-enhanced localized plasticity (The balance).