Abstract
Materials tested under cyclic loading in aggressive electrolytes suffer different kinds of localized damage which compete or superimpose mechanical fatigue. Fatal damage is influenced by both mechanical and (electro-)chemical parameters. In the present study an austenitic stainless steel has been tested in corrosive electrolytes ranging from mild to aggressive conditions by changes in salt-cation, pH-value, chloride content, temperature and R-value. To study the effect on S/N curves and especially on the fatigue limit, the type of damage was determined by investigating fracture surfaces using scanning electron microscope (SEM). In addition electrochemical properties of the steel in the testing solutions were ascertained by cyclic polarization. Furthermore scratch tests were conducted to characterize the materials repassivation kinetics.
This work aims to contribute to an improved understanding of the relation between environmental conditions and corrosion fatigue behavior of austenitic stainless steel. The results show the effect of different types of localized corrosion on the material performance under cyclic loading. Depending on the testing conditions pitting and stress corrosion cracking interfere with corrosion fatigue, leading to reduced fatigue strength. Comparing the influence of the occurring types of damage on fatigue strength, stress corrosion cracking turns out to be far more severe than pitting. Electrochemical tests and repassivation kinetics are suitable, but limited instruments to deduce the corrosion fatigue behavior.
