Scanning Electron Microscopy Analysis of the Interfacial Failure of Oxide Scales on Stainless Steels and Its Effect on Sticking during Hot Rolling.

Despite various strategies to address sticking failure in stainless steels (STSs), difficulties in understanding its fundamental mechanisms hinder precise solutions during STS fabrication. This study investigated the effect of chromium (Cr) content on the microstructures and failure modes of oxide scales under a tensile load, simulating the hot-rolling process. The dynamic, real-time behavior of crack initiation, propagation, and interfacial delamination in the oxide scales under tension was analyzed using an scanning electron microscopy (SEM) tensile test. With a high Cr content, iron (Fe) oxide and chromium(III) oxide (CrO) form a layered structure, which is delaminated along the interfaces between the thin CrO layer and the bulk after perpendicular cracking. The saturated crack densities obtained from SEM provide interfacial strength, while the elastic modulus and hardness obtained from nanoindentation provide vertical fracture strength. In combination with an elemental image analysis, the SEM results reveal three different failure modes of the four different STSs. The results confirm that sticking failure is more likely to occur as the Cr content increases.