Corrosion fatigue behavior of Alloy 690 steam generator tube in borated and lithiated high temperature water

Corrosion fatigue behavior of Alloy 690 tube used for actual steam generator (SG) was investigated in <5 ppb (by weight) dissolved oxygen borated and lithiated high temperature water by low cycle fatigue tests with boat-shaped specimens. It was found that the present tube materials had longer fatigue life than round-bar materials in open literature. The surface cracks were tortuous, typical crack branching and linkage were observed. The fracture surfaces were rough with well-defined fatigue striations. Related mechanisms of fatigue crack initiation and propagation of Alloy 690 SG tube in high temperature water are discussed.