he behavior and mechanism of
corrosion fatigue for A508 steel in
distilled water were stydied by means of a displacement
controlled cantilever bend fatigue machine as well as by fractographic and eledtrochemical techniques. The fatigue tests were performed at R=0, f=0.5Hz in ambient air
distilled water at various temperatures. It was showed that the fatigue crack growth rates of A508 steel in distilled water were 4 to 6 times faster than that in ambient air, and that they decreased with increase in water temperature at 15-80℃. This was precisely related to the reduction of dissolved oxygen contents,
corrosion potential and quantity of Fe2O3 in oxide film, and this agreed closely with the decrease in percentage of I.G. fracture with increasing water temperature. According to these data, it was suggested that the fatigue of A508 steel in distilled water should be considered as a true corrosion fatigue since no stress corrosion cracking occured and that the crack propagation might be controlled by anodic dissolution and simple fatigue rupture. A possible model was proposed in that local attacks occured,at the fracture front and the ligaments between these areas experienced a higher effective △K, resulting in mechanical rupture. The measured data were in reasonable agreement with the predicted curves of da/dN ～△k from this ligament model, △keff = △Kapp/(1-αC).