Influence of vanadium on the hydrogen embrittlement of aluminized ultra-high strength press hardening steel

Improved safety standards and reduced automotive body-in-white weight have led to a strong interest in martensitic press hardening steel (PHS). As the sensitivity to hydrogen embrittlement of martensite increases at higher strength level, the very small uptake of diffusible hydrogen by aluminized PHS during the austenitization stage of the hot press forming process is of concern. The hydrogen uptake was found to reduce the plasticity of the PHS considerably. The PHS with a higher strength was more susceptible to hydrogen-induced brittle fracture. The present work reports that vanadium additions, which serve to trap the hydrogen, considerably reduce the negative impact of the hydrogen uptake in aluminized 1800 MPa and 2000 MPa PHSs. The contribution also proposes a mechanism for the uptake of hydrogen during the processing of aluminized PHS.