The influence of aqueous environment of coolant of power plants on cyclical crack resistance of steels

The results of investigations of cyclic corrosion crack resistance of carbon steel of grade 20 and low-alloyed pipe steels of grade 15GS and 12Kh1MF are presented. The variants of water standard conditions of power plants are used as test environments. A significant activating impact of the aquatic environment on the kinetics of growth of fatigue cracks of the steels under study is shown. The most significant corrosive effect is observed when tested in an aqueous environment with addition of organic acid. In the low-frequency range of cyclical loading (0.04–0.0008 Hz), the frequency does not influence the characteristics of the cyclic corrosion crack resistance of steels. To eliminate the influence of stress cycle asymmetry on the diagram of corrosion-fatigue crack resistance of steels, it was proposed to use as a parameter of crack growth rate (CGR) the effective range of stress intensity factor (SIF), functionally associated with the factor of stress cycle asymmetry. When the temperature of the medium is increased from 80 to 150°C and to 280°C, the form of kinetic diagram of cyclic corrosion crack resistance is changed, resulting in a decrease in crack growth rate at the middle and upper sections of the diagram.