Equivalent hydrogen fugacity during electrochemical charging of some martensitic advanced high-strength steels

A new thermal desorption spectroscopy apparatus was used to study hydrogen in four martensitic advanced high-strength steels (designated MS980, MS1180, MS1300 and MS1500) after gaseous hydrogen charging, and after hydrogen charging electrochemically in 0.1 M NaOH and in 3.5 wt.% NaCl. The hydrogen concentration did not correlate strongly with steel strength. For MS1500, a relationship was derived between equivalent hydrogen fugacity and the applied charging overpotential. Also for MS1500, the trap binding energies were evaluated to be 26.4 kJ mol−1 and 61.0 kJ mol−1, which were interpreted as dislocation and interface hydrogen traps.