Stress Corrosion Cracking of a SUS304 Stainless Steel in MgCl2 Solution

Abstract

Stress corrosion cracking of a SUS304 stainless steel in boiling MgCl2 solution was studied fractographically with the aid of etch-pitting technique. An examination was also made on the applicability of linear fracture mechanics to SCC crack propagation. Fracture mode changed from transgranular to mixed intergranular-transgranular and again back to transgranular with an increase of stress intensity. The orientation of the transgranular fracture was predominantly {100} in fracture surface and <110> in propagating direction in the low stress region and changed to {110} surface and <110> direction in the high stress region. These fractures are likely to be caused by the complex effects of a number of mechanisms such as interaction of sessile dislocations or slip lines with chemical environment and decrease of surface energy in chemical environment. The linear fracture mechanics failed to valid in the high stress region where significant creep deformation was observed.