在位移可控的悬臂梁弯曲疲劳试验机上，对核电钢Ａ５０８在２０～８０℃蒸馏水中的腐蚀疲劳特性进行了初步探讨，并结合电化学和断口分析，对其裂缝扩展机制进行了研究。结果表明，Ａ５０８钢在蒸馏水中的裂缝扩展速率比在空气中的快４～６倍。在所研究的范围内，其ｄａ／ｄＮ随温度上升而下降。这与温度升高，水中的溶解氧量降低，腐蚀电位下降，钝化膜中的Ｆｅ２Ｏ３比例减少正好相对应；也与温度升高，断口中的沿晶断裂百分比下降完全吻合。在试验范围内，Ａ５０８不会发生应力腐蚀开裂，属真腐蚀疲劳，其裂缝扩展由阳极溶解和纯疲劳断裂两个因素共同制约。最可能的模型是：在裂缝前沿，首先在某些局部微区发生侵蚀，这些微区之间便形成韧带，承受较高的有效应力强度因子幅值△Ｋｅｆｆ，从而导致机械撕裂。而这些韧带的断裂过程，控制着腐蚀疲劳的扩展。将实验结果与据此提出和韧带模型△Ｋｅｆｆ＝△Ｋａｐｐ／（１－αＣ）的估算值进行比较，两者十分吻合。 The corrosion fatigue characteristics of A508 steel in distilled water at 20 ~ 80 ℃ were investigated on a controlled displacement cantilever bending fatigue tester. The mechanism of crack propagation was also studied by combining electrochemical and fracture analysis. The results show that crack propagation rate of A508 steel in distilled water is 4 to 6 times faster than in air. Within the range studied, its da / dN declines with increasing temperature. This corresponds to the increase of temperature, the decrease of dissolved oxygen in water, the decrease of corrosion potential and the reduction of Fe2O3 in the passivation film. It also coincides with the decrease of the percentage of intergranular fracture in the fracture caused by the increase of temperature. Within the test range, A508 does not occur stress corrosion cracking, is a true corrosion fatigue, the crack expansion by the anode dissolution and pure fatigue fracture of two factors together. The most probable model is that at the fracture front, erosion first occurs in some of the local micro-regions, and ligaments are formed between these micro-regions, subjecting to a high effective stress intensity factor, Δ Keff, resulting in mechanical tearing. The rupture of these ligaments, control the expansion of corrosion fatigue. The experimental results are in good agreement with the estimates of △ Keff = △ Kapp / (1-αC) presented here and the ligament model.