Hydrogen embrittlement of FeCrAl alloys: The significant role of Laves phase and AlN particles

The addition of Nb to FeCrAl alloy enhanced its mechanical properties owing to the precipitated-phase strengthening effect. However, the additive amount and its effect on hydrogen embrittlement (HE) susceptibility have to be evaluated before implementation, as the hydrogen produced by fission and corrosion in the reactor may affect its mechanical properties. Therefore, hydrogen pre-charged tensile bar specimens were tested, and the HE mechanism was investigated. The results demonstrate that though FeCrAl alloys show low HE susceptibility, the Nb-doped FeCrAl alloys still exhibit a slightly higher HE susceptibility than Nb-free FeCrAl alloys. Their reduced ductility was mainly caused by decohesion and cracking of Fe2(Nb, Mo) precipitates and quasi-cleavage cracking induced by AlN inclusions. The underlying HE mechanisms for the Nb-doped FeCrAl alloys are hydrogen-enhanced localized plasticity (HELP) and HELP-mediated hydrogen-enhanced decohesion (HEDE). •FeCrAl alloys have low HE susceptibility, slightly increasing for the Nb adding.•AlN and Fe2(Nb, Mo) precipitates are the factors affecting HE susceptibility.•Quasi-cleavage cracking initiated from AlN is a common fracture in the alloy.•Premature cracking and decohesion of Fe2(Nb, Mo) occurred during the strain test.•The HE mechanisms of FeCrAl-xNb alloys are the HELP and HELP-mediated HEDE.