The interface between corrosion fatigue and stress-corrosion cracking

Abstract

Crack growth in a mild steel subjected to various cyclic loading conditions while immersed in a carbonate-bicarbonate solution and held at different potentials may follow intergranular or transgranular paths depending upon the test conditions. Different potentials can accelerate transgranular cracking, promote intergranular cracking, delay crack initiation, or have virtually no effect as compared to that observed when tests are carried out in oil at the same temperature. With such diverse responses it is unlikely that the interface between stress-corrosion and corrosion-fatigue cracking can be adequately described by a simple superposition model, but rationalization is possible if account is taken of the varying electrochemical reactions at different potentials, of the importance of strain-rate effects in the plastic zone, and of the relative rates of crack growth for different failure modes.