Investigation of SCC Mechanism of SUS 304 in Boiling 42% MgCl₂ Solution by Fractographic Observation

Abstract

Fracture surface of SUS 304 stainlests steel subjected to stress corrosion cracking (SCC) in boiling 42% MgCl₂ solution was investigated fractographically by scanning electron microscopy. To determine the orientation of fracture surface, etch pits were formed on the fracture surface by the electro-etching method in 1N H₂SO₄+100mg/L NH₄SCN solution. It was found that the fracture surface of SCC was mostly in {100} plane, which was determined by the morphology of etch pits. This shows that the crack path depends on the orientation of crystal grain and the direction of stress.