Dominant crack selection in multi-crack stress corrosion cracking of AISI 316L stainless steel under sustained loading in flowing HCl

Abstract

Abstract

Stress corrosion cracking (SCC) in structural components often involves the simultaneous development of multiple cracks; however, the mechanism by which a dominant crack emerges under sustained loading remains insufficiently resolved. This exploratory study investigates competitive multi-crack SCC behavior in AISI 316L stainless steel under sustained tensile loading in flowing 1 M HCl. Five naturally nucleated surface cracks formed around a central hole were monitored using repeated in situ optical imaging. Interval-based crack growth rates (Δa/Δt) were calculated from five discrete inspection times. Post-test fracture paths were analyzed, supported by SEM fractography and SEM–EDS to assess localized degradation. Fracture-path analysis showed that Cracks 3 and 4 controlled the final trajectory. Interval-based descriptors identified Crack 4 as kinetically dominant within the tested specimen, exhibiting the highest mean and maximum growth rates and the largest cumulative extension. SEM–EDS revealed localized degradation, secondary branching, higher oxygen content, and a detectable chlorine signal in the Crack 4 region. Within the tested multi-crack configuration, dominant-crack behavior could be distinguished using interval-based growth descriptors from discrete observations. The findings are consistent with a combined influence of stress redistribution and localized corrosion-assisted degradation and provide a proof-of-concept basis for comparing crack-growth persistence from discrete observations.