Mechanisms of stress-induced deterioration of corrosion resistance of the laser-desensitized 316L stainless steel

Abstract

Austenitic stainless steels (SS) frequently suffer severe corrosion degradation under mechanical stress, yet the atomic-scale mechanisms governing this ubiquitous phenomenon remain poorly understood. Here, we present a multi-scale study combining electrochemical analysis, x-ray photoelectron spectroscopy (XPS), aberration-corrected transmission electron microscopy (TEM), density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations to investigate the effect of elastic tensile stress on the passive film stability of a laser-desensitized 316L SS. It is found that increasing tensile stress dramatically degrades corrosion resistance, as evidenced by lower film resistance and intensified metastable pitting. XPS results confirm that degradation of corrosion resistance is linked to the promotion of detrimental Fe-oxides and a reduction in protective Cr₂O₃ content in the passive film. In addition, TEM analysis indicates that high tensile stress thickens the passive film by ∼18.6 % and transforms it into a vulnerable Fe-enriched and Cr-depleted structure. Theoretical simulations with both DFT and AIMD reveal that the outward diffusion of Fe driven by tensile elastic stress is thermodynamically favoured and kinetically accelerated. This work provides a novel understanding of stress-induced deterioration of the corrosion resistance of austenitic SS.