Effect of corrosion on the fatigue behaviour of butt welds of G20Mn5QT cast steel and Q345D hot rolled steel in 3.5‐wt% NaCl solution

Abstract

AbstractCorrosion fatigue experiments are carried out on butt welds of G20Mn5QT cast steel and Q345D hot rolled steel in simulated seawater. The cyclic stress versus number of cycles to failure (S‐N) curve was fitted. The mechanism of crack nucleation at different fracture locations and at different stress levels is analysed. The results show that compared with the S‐N curve of laboratory air, for the S‐N curve of simulated seawater, the number of fatigue failure cycles is significantly reduced when the maximum cyclic stress is less than 190 MPa. At higher stress levels, stress concentrations caused by internal defects near the surface of the weld zone and the heat‐affected zone of G20Mn5QT cast steel cause crack nucleation. At lower stress levels, the main reason for crack nucleation is the stress concentration caused by corrosion pitting. However, there are no obvious internal defects in the heat‐affected zone of the Q345D steel, and corrosion pitting is the main cause of crack nucleation. The stress concentrations caused by pitting lead to crack nucleation.