LAUSR

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 ( S max ) and various current densities (HCCD): (i) hydrogen-enhanced toughness ( S max  ≤ 0.6 σ p0.2 , HCCD ≤ 25 mA∙cm −2 ), (ii) hydrogen embrittlement ( S max  > 0.8 σ p0.2 , HCCD > 25 mA∙cm −2 ), (iii) hydrogen-enhanced localized plasticity (The balance).