Evaluation of chloride stress corrosion cracking susceptibility of stainless steels

The comparative chloride stress corrosion cracking (Cl-SCC) susceptibility for 304 L, 316 L, 317 L, and AL-6XN was evaluated using double cantilever beam (DCB) specimens in boiling MgCl 2 by measuring the threshold stress intensity (K ISCC ), crack initiation time, and stage-II crack growth rate (CGR) for each material using in situ monitoring. Materials 304 L, 316 L, and 317 L were measured to have K ISCC upper limit values of 2.5–5 MPa√m, substantially lower than previously measured for 304 L in DCB specimens in boiling MgCl 2 . The K ISCC for AL-6XN was measured to be substantially higher, as would be expected in this more highly alloyed material. This work describes the challenge in measuring low K ISCC values and how this was accomplished in the present work. More prototypical conditions were used to evaluate Cl-SCC behavior of 304 L using a DCB-like geometry with a smooth gauge area in a low humidity environment in the presence of MgCl 2 salt. Finite element modeling (FEM) was used to establish the relationship between applied loads and stress and strain. Loading to 15 % strain led to low temperature creep that masked in situ Cl-SCC measurements. Below the yield stress (YS), no low temperature creep was observed, and Cl-SCC cracking could be distinguished using in situ methods.