Tensile orientation dependence of hydrogen embrittlement in SUS304 stainless steel single crystals

Tensile tests were carried out on SUS 304 Stainless steel single crystals, whose respective tensile axes were parallel to [001], [111] and 0.5 in Schmid factor, under cathodic charging in 0.5 kmol/m3 H2SO4 solution with a small amount of NaAsO2 at room temperature, and the characteristics of hydrogen embrittlement of this material in tension were evaluated from the nominal stress-strain curve. The susceptibility to hydrogen embrittlement appeared prominently in the elongation and fracture morphology. The elongation decreased with increasing current density and the resulting fracture surface morphology changed from ductile to cleavage manner. The cracks produced by hydrogen initiated at the deformation bands and propagated perpendicular to the tensile axis, then connected each other and fractured. The orientation dependence of hydrogen embrittlement was recognized on the fracture morphology when the current density was between 4 to 10 A/m2. The morphology of fracture surface under the present test condition was dependent on both amount of martensite induced by deformation and the concentration of hydrogen.