Improvement of stress corrosion cracking resistance by low cycle fatigue of a CrNiMoV steel

Low cycle fatigue often interacts with stress corrosion cracking behavior. In this work, the effect of low cycle fatigue on stress corrosion cracking susceptibility of a CrNiMoV steel was investigated by interrupted fatigue tests in air and slow strain rate tensile tests in 3.5 wt% NaCl solution at 180 °C. Microstructure evolution characterization verified cyclic softening and was found to improve stress corrosion cracking resistance with crack deflection along lath martensites due to a decrease of residual stress, phase transformation and increase of low-energy structures. As a semi-quantitative damage indicator, the microstructure evolution due to low cycle fatigue damage can be well described by the Kernel Average Misorientation (KAM) from the Electron Backscatter Diffraction technique. The effect of fatigue damage on stress corrosion sensitivity was found predictable based on the linear relationship between KAM and stress corrosion sensitivity factor of reduction of area.