Abstract: Mean stress is an important factor affecting the corrosion fatigue strength of metallic materials. Endurance limit diagrams plotted on the basis of tests under different mean stress levels provide the fundamental knowledge for fatigue design. The influence of mean stress on fatigue properties in the corrosion environment is different from that in the air. This feature should be taken into sufficient consideration. In the present research, the corrosion fatigue limits of ZG20SiMn and ZG0Cr13Ni4Mo under different stress ratios in fresh water were obtained by the tests. The results show that mean stress had a stronger effect on the corrosion fatigue strengthes of the two kinds of materials than those in the air. If the endurance limit diagrams obtained in the air were used as criterion for engineering design under the corrosion fatigue condition, the results would be unsafe. The fracture surfaces were examined using scanning electron microscope and the possible mechanism was discussed.

Key words: 腐蚀疲劳, 疲劳极限图, 平均应力