Mitigating hydrogen embrittlement in a 1.8 GPa-grade press-hardened steel by internal stress relaxation via low-temperature tempering

Abstract

Recently, new categories of press-hardened steels (PHS) with an ultimate tensile strength (UTS) of up to 1.8 GPa have been developed to meet the increasing demand for lightweight vehicles. However, these ultra-high strength PHS are highly susceptible to hydrogen embrittlement (HE). The present work demonstrates for the first time that the HE of PHS can be mitigated through tempering treatment at 90 °C without sacrificing tensile strength. The improved HE resistance can be attributed to the relaxation of internal residual stress and the reduction of hydrogen diffusion rate caused by the low-temperature tempering.