Near boundary gradient zone and sensitization control in austenitic stainless steel

The dependence of degree of sensitization on partially deformed (rolled and then sensitized) microstructure of 304L stainless steel was investigated. Structures with visible grain fragmentation, or clear reductions in grain size, showed a poor resistance to sensitization. However, non-fragmented deformed grains with clear presence of near boundary orientation gradients provided an improved resistance. Bulk statistical data were further corroborated through direct observations from electron backscattered diffraction (EBSD) and white light interferometry (WLI). EBSD quantified the near boundary gradient zones (NBGZ) while WLI characterized localized corrosion. Scaling between grain average depth of attack and dimension of NBGZ was established.