H2SO4-NaCl溶液中における310鋼のき裂進展速度と溶解速度の関係

Abstract

Relationship between crack propagation rate and dissolution rate of type 310 stainless steel was studied to clarify the effect of the lattice defects on crack initiation and crack propagation in H2SO4-NaCl solutions.Stress corrosion morphology changed in order of general corrosion, localized corrosion, stress corrosion cracking with increasing NaCl concentration. Stress corrosion cracking was observed at the potential range of active region on an anodic polarization curve. Dissolution rates of prestrained specimens were increased with increasing the dislocation density. Optical micrograph showed the formation of corrosion grooves and dissolution rates of these corrosion grooves are close to the crack propagation rates under low initial stress intensity. Transmission electron microscopic observation showed the existence of bundle structure that is high dislocation density region like a plane. As the dissolution rate was accelerated with increasing the dislocation density, this corrosion grooves might be formed by the preferential dissolution of bundle structure.From these results, it is thought that the crack initiation and the propagation are accelerated with preferential dissolution of bundle structure.