The branching and growth mechanism of stress corrosion cracks in quenched-and-tempered SNCM 8 steel in 3.5% NaCl solution was analysed from a view point of fracture mechanics. The intermittent crack growth behavior was detected. The crack increment in each step of discontinuous crack growth was smaller than the plastic zone size and larger than the twice of the crack tip opening displacement. The crack branching mode was shown to be strongly dependent upon the tempering temperature. The effect of crack branching on crack growth kinetics was separately discussed based on a mechano-chemical model of stress corrosion cracks.
