The influence of microstructure on hydrogen diffusion and embrittlement of fine-grained high strength dual-phase steels

Abstract

The permeation experiments performed in this study have shown that electrochemical corrosion of dual-phase steels in 2 mol L-1H2SO4results in hydrogen evolution and absorption of hydrogen atoms in the material, which leads to degradation known as hydrogen embrittlement (HE). The values of the diffusion coefficient and hydrogen solubility obtained in this study have shown that transport of diffusible hydrogen and high susceptibility to HE depends on different microconstituents acting as hydrogen traps in dual-phase steels. The metallographic and SEM/EDS analyses have revealed elongated inclusions in dual-phase steel marked as DP, acting as irreversible traps in the ferrite-martensite matrix. Room temperature tensile tests of hydrogenated specimens have shown degradation of elongation and contraction compared to those of nonhydrogenated ones. SEM analyses of fracture surfaces have revealed the difference between nonhydrogenated dual-phase steels with ductile fracture and hydrogenated dual-phase steels with brittle fracture.