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

https://doi.org/10.3221/IGF-ESIS.79.02

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.