Hydrogen embrittlement behavior of two mining chain steels by slow strain rate test

Two mining chain steels 23MnNiMoCr5-4 and 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) with tensile strengths of 1200 MPa and 1250 MPa, respectively, were employed to investigate their hydrogen embrittlement behaviors by slow strain rate tests combined with thermal desorption analyses. It is shown that at initial stage the fracture stress decreases linearly as the hydrogen content increases, and the turning points occur at hydrogen content of 1.2 wppm for 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) and 0.26 wppm for 23MnNiMoCr5-4. The fractured surface observation suggests that the ratio of intergranular fracture area to quasi-cleavage area increases dramatically at the turning points. The maximum hydrogen contents resulting from the corrosive HCl solutions with pHs of 2 are approximately 0.6 wppm 0.3C0.2Si0.3Mn4.2(Cr+Ni+Mo) and 0.11 wppm for 23MnNiMoCr5-4, corresponding to the activation energies for hydrogen desorption are 21.57 kJ/mol and 14.53 kJ/mol, respectively.