Effect of Mn alloying on the hydrogen‐assisted cracking behavior in multiphase/duplex stainless steel

There remains debate on whether Mn is beneficial or detrimental to hydrogen embrittlement in stainless steel. In this work, a series of stainless steels were designed to study the change of hydrogen embrittlement sensitivity, crack propagation, and hydrogen trapping behaviors upon Mn addition. The results suggest that adding 4 wt.% Mn increased hydrogen embrittlement susceptibility, whereas adding 8 wt.% Mn decreased hydrogen embrittlement sensitivity. Forming banded α'-martensite through austenitic grain is the main reason for the increased hydrogen embrittlement sensitivity when adding 4 wt.% Mn, by adsorbing hydrogen, promoting crack initiation, and accelerating crack propagation.