Corrosion Fatigue Behavior of Low-Alloy Pressure Vessel Steels in High Temperature Water Under Multi-Factor Conditions

The corrosion fatigue resistance of pressure vessel steels in simulated light water reactor coolant water is greatly influenced by the mechanical factor such as strain rate, environmental factor such as temperature and dissolved oxygen (DO) concentration in water, and material factor such as sulfur content in steels. In most of previous work, the mechanical or environmental conditions were usually fixed as a constant throughout an individual test. However, these factors may change frequently during actual operations in power plants. So, it is of great interest to investigate the effects of change of the above factors on fatigue resistance of components materials in service environments and to develop appropriate methods for evaluating the environmental effects on fatigue damage. The present work was to investigate the low cycle fatigue (LCF) behavior of low-alloy pressure vessel steels in high temperature water. Special attention was paid on the influence of strain rate change in an individual LCF test on fatigue resistance of the steels. The alternate sequence of strain rate in a test was also considered. Moreover, the influence of DO, temperature and sulfur content in the steels was investigated. The detailed cracking and fractographic features were examined to assist the understanding of underlying corrosion fatigue mechanisms.