Characterization of hydrogen traps in a co-precipitation steel investigated by atom probe experiments without cryogenic transfer

Hydrogen (H) embrittlement in high-strength steels can be mitigated by introducing H traps into the microstructure. The co-precipitation model steel in this work contains intermetallic ß-NiAl and secondary Cr-carbides, which provide abundant trapping sites. Needle-shaped specimens are prepared for atom probe tomography (APT) and electro-chemically charged in a solution of 0.1 M NaOH in D2O to introduce deuterium (D). D is located at the finely dispersed Cr-carbides even after specimen transfer at room temperature (RT), which shows that nano-sized Cr-carbides are strong H traps. This is in contrast to previous studies of weak traps where cryogenic transfer was needed to detect any D.