Experimental study on the effect of strain amplitude on environmental fatigue life of domestic forging austenitic stainless steel

Abstract Background: Environmental assisted fatigue (EAF) is the important issue in the field of fatigue analysis, assessment and safety regulation of pressurized water reactor nuclear components. Some factors affect fatigue life of materials and related mechanisms. Purpose: The aim is to verify the influence of simulated pressurized water reactor coolant environment on the fatigue life of domestic forging main coolant pipe made of austenitic stainless steel. Methods: Fatigue tests were conducted using high-temperature and high-pressure water fatigue testing system, and standard round-bar fatigue specimen made from product forging. Results: The relationship between test data and American Society of Mechanical Engineers (ASME) code fatigue mean/design curve was analyzed. The effect of strain amplitude on fatigue life of austenitic stainless steel was investigated and the suitability of ASME code fatigue design curve and fatigue life environmental correction factor were preliminarily evaluated. Conclusion: The fatigue life of forged 316LN stainless steel in high-temperature and high-pressure water are lower than those at room temperature in air. The environmental degradation is more obvious under low strain amplitudes than that under high strain amplitudes. The best-fit curve based on the updated Argonne National Laboratory (ANL) model is recommended for the fatigue design of domestic austenitic stainless steel. The environmental effect should be incorporated into the fatigue design of domestic austenitic stainless steel. The fatigue crack mainly initiated from the surface micro-pits and slip bands for the domestic forged austenitic stainless steel in high-temperature and high-pressure water. (authors)