Influence of mean stress and pressurized water reactor environment on the fatigue behavior of a 304L austenitic stainless steel

Uniaxial strain‐controlled fatigue tests were carried out on a 304L austenitic stainless‐steel specimens in air at 300°C and in pressurized water reactor (PWR), without or with the application of a mean stress, at different total strain amplitudes. For strain amplitude no less than 0.2%, a deleterious effect of PWR water on fatigue life is observed, associated with the enhancement of both crack initiation and propagation. Besides, the fatigue life is reduced by the application of a mean stress for a fixed strain amplitude in a given environment. In particular, due to the acceleration of crack initiation stage by an enhancement of the plastic strain accumulation, the PWR water effect on fatigue life is re‐activated for strain amplitude below 0.2% in the presence of a mean stress. The fatigue life reduction under mean stress application is mostly related to the maximum stress level and strain amplitude, rather than the generated ratcheting strain. The results of strain‐controlled fatigue tests in air and in PWR water are presented. The application of a mean stress affects the fatigue strength in both environments. The effect of environment and mean stress on initiation and propagation is analyzed. A modified SWT equation is proposed.