Mechanistic Aspects of Intergranular Stress Corrosion Cracking of Ferritic Steels

Abstract

Evidence of intergranular attack (IGA) in the absence of stress, together with dissolution kinetics, indicates that intergranular stress corrosion cracking (IGSCC) of ferritic steels in various environments is by a dissolution mechanism. Film rupture can play an important role in the rate of growth of cracks, but film rupture is not the mechanism of growth. The dual requirements of dissolution and filming to sustain crack growth in the crack-tip region indicate the need for the system to display an active-to-passive transition in those regions of potential where cracking occurs, and such are observed. The localization of dissolution in grainboundary regions results from the presence of segregates or precipitates, but appropriate measurements are needed in this area if some details of the cracking mechanism are to be understood fully.