Hydrogen embrittlement resistance of 400 km/h high-speed train wheel steel: Assessment via thermal desorption spectroscopy and slow strain rate tensile testing

In this investigation, the hydrogen embrittlement susceptibility (HES) of the CLD400 high-strength wheel steel for 400 km/h trains was investigated using thermal desorption spectroscopy (TDS) and slow strain rate tensile (SSRT) testing. The wheel steel was subjected to electrochemical hydrogen charging for 24 to 72 hours, and its hydrogen content and hydrogen traps were analyzed via TDS experiments. The activation energy of reversible hydrogen traps in the wheel steel is 30.6 kJ/mol, with the ferrite/cementite (F/Fe 3 C) interface being the dominant form of hydrogen trapping. Refined pearlite lamellae and strained F/Fe 3 C interfaces exhibit strong hydrogen-trapping capabilities. SSRT tests demonstrated that the CLD400 wheel steel exhibits excellent hydrogen embrittlement resistance, with an HES comparable to that of the ER8 wheel steel that is currently used for 350 km/h trains, which has lower strength. Hydrogen-induced cracks originate at the pearlite colony/ferrite grain boundary and F/Fe 3 C interface and can propagate both transgranularly and intergranularly. The multimorphological polymorphic F/Fe 3 C interface significantly inhibits the diffusion of hydrogen atoms and the propagation of hydrogen-induced cracks, thereby increasing the hydrogen embrittlement resistance of the CLD400 steel.