Study on the mechanism of high-cycle corrosion fatigue crack initiation in X80 steel

Corrosion fatigue experiments on X80 steel in 3.5% NaCl solution were conducted on a researcher-developed cantilever-bending corrosion fatigue testing machine. The morphology of corrosion pits and the change in the surrounding microstructure were carefully examined using SEM and TEM, and the stress field was simulated using the finite-element method. The results show that the corrosion fatigue crack initiation is due to not only the corrosion pits’ stress concentration effects but also the adhering corrosion products. Corrosion products formed on the surface of slip bands, and the action of corrosion products on fatigue crack initiation was explained using physical models.

► We examine corrosion fatigue morphology and change in microstructure of test sample.
► We model the acting process of corrosion products on crack initiation.
► Slip bands appears under very low load because of stress concentration.
► Iron oxides on slip bands may intrude into steel substrate under cyclic load.
► Corrosion products cause irreparable damage in steel.