The stress corrosion cracking (SCC) of SUS 310S stainless steel having coarse grain structure in boiling MgCl2 solutions was studied fractographically by a scanning electron microscope. The crystallographic orientation of transgranular fracture mode in SCC was determined with the aid of etch-pitting technique.
The mode of crack propagation during SCC-tests depended on the orientation of coarse grain, and the crack growth showed a delay of several ten minutes at grain boundaries, twin boundaries or crack branching points. On the other hand, the mode of transgranular fracture was characterized by a fan-shaped pattern, which was formed mostly by the crack growth along <110> direction on {100} plane. On this fracture surface, a striation-like pattern was found locally as the result of slip lines formed perpendicular to the direction of crack growth.
The above results imply that the transgranular fracture in SCC occurs crystallographically by the interaction of sessile dislocation with corrosive environment.
