Abstract
Maraging steel is the material of deep sea pressure equipment. The characteristics of corrosion fatigue crack initiation in 18Ni (250) were investigated by performing a tensile fatigue test under different loading conditions. The mechanism of corrosion fatigue crack initiation was analyzed considering the influence of welding. The results showed that the crack initiation life decreases with increasing load and increases with the stress ratio. In a corrosive seawater environment, crack initiation is affected by both mechanical damage and electrochemical corrosion. The proportion of the crack initiation life of the total sample life is approximately 71.45–99.55%, where the larger this proportion is, the smaller the fatigue zone is. Crack initiation and microcrack propagation in maraging steel correspond to the microfracture mechanism of dimple fractures. The microfracture mechanism is strongly affected by the presence of a weld but weakly affected by the weld position. The results of this study provide a theoretical basis for predicting the corrosion fatigue life of deep-sea submersible pressure hulls.
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