Effect of plastic strain damage on the hydrogen embrittlement of a dual-phase (DP) and a quenching and partitioning (Q&P) advanced high-strength steel

The hydrogen influence on two 1180 MPa advanced high-strength steels was studied using electropolished U-bend specimens in HCl solutions of pH 1 and pH 3. Bending limit diagrams identified conditions for safe use. Hydrogen-assisted fracture occurred only near the bending limit, and was promoted by microvoids and microfractures, introduced by the severe plastic deformation of the U-bend specimens. The hydrogen fracture initiation and early propagation was by the mechanisms designated as hydrogen fracture due to hydrogen enhanced microvoid coalescence (HFMVC). Exploratory work indicated that fractures were critically dependent on the surface state of the specimens.