Design of a New Stress Corrosion Cracking Test for Austenitic Stainless Steel Welds

Stress corrosion cracking (SCC) in austenitic stainless steel (SS) welds remains a complex challenge due to the interplay of metallurgical heterogeneities and environmental parameters. This study proposes a new accelerated SCC test designed to evaluate the SCC susceptibility of 316L SS welds under conditions that better simulate in-service environments. The newly designed test is a uniaxial tensile test which incorporates incremental loading combined with anodic polarization cycles in a 1 M NaCl solution acidified to pH 4 at 60°C, i.e., a solution more representative of in-service applications than the usual boiling MgCl2 often used in the literature. Tensile specimens were machined to align the weld axis with the loading direction, and 1-mm diameter stress concentrators (i.e., holes) were strategically located between the fusion zone (FZ), heat-affected zone (HAZ), and base metal. When the tensile loading was incrementally increased to 450 MPa, fracture of the tensile specimen was observed. Fractographic analysis confirmed crack initiation in the HAZ and unstable propagation toward the FZ. Two reference tests were performed for comparison. For one reference test, the same methodology was used, but without stress concentrators: only microcracks were observed, primarily intergranular in nature and concentrated in the HAZ, validating this zone as the most susceptible to SCC. Another reference test used the tensile specimen with stress concentrators, but it was conducted at open-circuit potential (OCP) for one month. This long-term test demonstrated similar failure patterns and corrosion mechanisms as the newly designed test, confirming its representativeness despite anodic polarization. The newly designed test successfully accelerates SCC while preserving the relevance of observed damage modes, bridging the gap between traditional accelerated methods and actual service conditions. The findings emphasize the critical role of the HAZ in SCC initiation, as well as the influence of microstructural features and stress and deformation gradients. This methodology offers a robust framework for screening SCC resistance in welded SS components and for further mechanistic studies under controlled but representative conditions.