Fracture Path of Stress Corrosion Cracks in Austenitic Stainless Steels

Abstract

THE phenomenon of transgranular stress corrosion cracking of austenitic stainless steels in aqueous chloride environments has been recognized for almost 30 yr¹. One fact that has had to be included in establishing the mechanism is that the fracture has appeared not to progress along any particular crystal plane². Only one study³ of single crystals has been reported. Back reflexion Laue photographs revealed that fracture followed no particular plane in specimens of 18Cr–10Ni or 20Cr–12Ni alloys but that it followed {100} planes in specimens of 20Cr–20Ni alloy. In this article we show, by scanning electron microscopy, that the crack follows a crystallographic path even in 18Cr–10Ni steels—an observation not made before. It has been widely suggested that cracks propagate perpendicularly to the operative tensile stress component on both a macro⁴ and a micro⁵ scale.