Layer-by-layer analysis of gradient corrosion behavior of ultrasonic rolling-processed 20CrMnTi steel

Abstract

The gradient corrosion behavior of 20CrMnTi treated by the ultrasonic surface rolling process (USRP) was investigated by layer-by-layer analysis. As the nanostructured layer gradient changed from the surface to the interior, multiple electrochemical behaviors were studied at different depths in a neutral corrosive environment. The results showed that the corrosion resistance of the deformed layer underwent a nonmonotonic transition. Although the outer surface exhibited excellent corrosion resistance, this resistance decreased sharply and reached a minimum at a depth of 50 μm. This study showed that the corrosion resistance at different depths was mainly influenced by the density of low-angle grain boundaries (LAGBs) rather than by the grain size. The highest LAGB density was observed at depths of 30–50 μm, resulting in the greatest lattice distortion that induced the lowest corrosion resistance.