A crystallographic study on stress corrosion cracking of SUS 310S steel single crystals.

The effect of tensile axis on stress corrosion cracking (SCC) of SUS 310S steel single crystals in a boiling MgCl2 solution (42%) at 416K was studied under the constant-loading conditions.The threshold stress for SCC decreased in order of tensile axes of [111], [101] and [001], and was independent of Schmid factors for the primary slip system. Cracks were preferentially nucleated from the micro-pits at slip steps by plastic deformation and grew along the ‹110› direction on the {100} plane in every type of specimens. The fracture surface of [001]-oriented specimen was observed to be flat, but those of the rest contained steps composed of other {100} planes, too. It was found that the normal stress to the {100} crack plane vs. fracture time curves in all types of specimens coincided well. This fact suggests that the crack growth is strongly controlled by the normal stress to the {100} plane which makes the smallest angle with respect to the tensile axis.