A critical review on very high cycle corrosion fatigue: Mechanisms, methods, materials, and models

Determining the long-term corrosion fatigue strength of structural materials in service conditions is one of the most significant problems of the design engineer. Synergistic interactions between mechanical fatigue effects and environmental factors may be more harmful than the total effects of each mechanism working alone. Current understanding is inadequate to handle life estimate with a good physical foundation, from the onset of localized corrosion (such as pitting) through the estimation of fracture propagation. Considering that a corrosion phenomenon is a time-dependent event, the extended fatigue life of the components, exposed to a corrosive environment, is a key concept to comprehend to design safely against corrosion and ultralong life fatigue failure. Utilizing In-situ (or ex-situ) ultrasonic fatigue testing, the ultralong-life fatigue and corrosion behavior of structural materials in a very high cycle regime could well be studied. In this article, the benefits of ultrasonic fatigue testing, including screening tests' efficiency, acceleration, reliability, and the research of fatigue and corrosion fatigue behavior in very high cycle regimes are mostly described. The focus of this state-of-the-art review paper will be on the significance of corrosion pits and the interaction between mechanical cycling and corrosion pitting in the very high-cycle corrosion fatigue fracture initiation stage. The paper starts with an introduction to various mechanisms of corrosion fatigue. It then continues with a general description of very high cycle fatigue (VHCF) and very high cycle corrosion fatigue (VHC-CF) and then continues with the characterization of VHCF and VHC-CF of conventionally and additively manufactured materials. This review article also analyses available VHC-CF crack models in both conventionally-fabricated and additively manufactured metallic materials. Finally, a comprehensive summary of the needs, importance, and applications of VHC-CF has been provided in the current review paper.