Microstructure and Mean Stress Effects on Fatigue Behavior of Type 304L Stainless Steel

Pegues, J. W., Lugo, M., & Shamsaei, N. (2015). Microstructure and Mean Stress Effects on Fatigue Behavior of Type 304L Stainless Steel. 15th International ASTM/ESIS Symposium on Fatigue and Fracture Mechanics. 40th National Symposium on Fatigue and Fracture Mechanics, Anaheim, CA: ASTM International.

Abstract

Stainless steels are used for structural components in the chemical, nuclear, construction, food, and transportation industry as they possess an exceptional combination of mechanical and corrosion properties in many different environments. In several of these applications, the components are subjected to repeated loads which may lead to their failure due to fatigue. Despite the fact that the cyclic behavior of the stainless steel type 304 has been investigated for decades, limited amount of literature exists on the influence of the microstructure on fatigue performance for this alloy. The objective of this work is to identify the effects of microstructure and strain ratio on the cyclic behavior and fatigue life of a type 304L stainless steel. A set of uniaxial strain controlled fatigue tests at different strain ratios are conducted. The effects of mean stresses on the cyclic behavior and fatigue are addressed. Scanning electron microscopy (SEM) is used to study the failure mechanisms and transition regions. Microstructure evolution during cyclic loading is observed in order to investigate the strain-induced phase transformation occurring at different stages of damage. Additionally, electron backscatter diffraction (EBSD) is employed to evaluate the martensite phase transformation at different strain levels. Microstructure evolution and EBSD observations are used to establish structure-property relations associated to cyclic damage. Finally, the secondary cyclic hardening typically observed in this material is discussed based on microstructure evolutions.