| Abstract Scope |
Surface finishing processes significantly influence near-surface microstructure of austenitic stainless steels (SSs) with different stacking fault energies (SFE). While SFE-dependent phase transformations are well understood, the impact of surface finishing on mechanical properties at the surface remains unclear. This study systematically evaluates how surface preparation affects microstructural evolution and mechanical behavior in 304 SS (low SFE) and 310 SS (high SFE). Three surface finishing protocols were employed: electropolishing in perchloric-acetic acid, mechanical polishing with SiC to 2.5 μm, and colloidal silica polishing to 0.05 μm. Characterization included cross-sectional scanning electron microscopy (SEM), 3D optical profilometry, X-ray diffraction (XRD), nanoindentation, and transmission electron microscopy (TEM) analysis. Results demonstrate strong coupling between surface finishing and SFE in determining deformation mechanisms. Notably, mechanically polished 304 SS specimens exhibited significant subsurface plastic deformation and localized γ→α' martensitic transformation, while electropolished 304 SS showed minimal phase transformation. Conversely, 310 SS maintained predominantly austenitic microstructure across all surface conditions, showing limited dislocation activity without phase transformation. Surface finishing creates distinct subsurface deformation fields that interact with intrinsic SFE to govern phase stability and surface mechanical properties. These findings provide fundamental insights for optimizing surface treatment protocols, enabling improved control over near-surface mechanical properties and phase stability in structural applications. |