Hydrogen Dragging by Moving Dislocation and Enhanced Lattice Defect Formation in 316L and 304 Stainless Steels

Little is known about an enhanced lattice defect formation due to an interaction between hydrogen and dislocation in face-centered cubic (fcc) metals such as stainless steels. In the present study, hydrogen spectra evolved from Type 316L and 304 stainless steels during elastic and plastic deformation were detected using a quadrupole mass spectrometer. The amount of lattice defect enhanced by hydrogen and strain was measured using thermal desorption analysis. For 316L stainless steel, hydrogen desorption increased rapidly when plastic deformation began, since the dislocation dragged hydrogen to the surface of the specimen. In contrast, hydrogen desorption increased with applying strain for 304 stainless steel, because of phase transformation from austenite into martensite with larger hydrogen diffusivity. And the amount of desorbed hydrogen increased with decreasing strain rate. These results indicate that dislocation can drag and transport large amounts of hydrogen when the dislocation velocity approaches the hydrogen diffusion rate. The amount of lattice defects in stainless steels was enhanced by hydrogen and applied strain. The most probable reason for the increase in the amount of lattice defects can be ascribed to the increase in the amount of vacancy clusters. These findings lead to the conclusion that the interaction between dislocation and hydrogen enhances the formation of vacancy clusters, as a result, causes hydrogen embrittlement.