Crystallographic effects on transgranular chloride-induced stress corrosion crack propagation of arc welded austenitic stainless steel

Abstract

The effect of crystallography on transgranular chloride-induced stress corrosion cracking (TGCISCC) of arc welded 304L austenitic stainless steel is studied on >300 grains along crack paths. Schmid and Taylor factor mismatches across grain boundaries (GBs) reveal that cracks propagate either from a hard to soft grain, which can be explained merely by mechanical arguments, or soft to hard grain. In the latter case, finite element analysis reveals that TGCISCC will arrest at GBs without sufficient mechanical stress, favorable crystallographic orientations, or crack tip corrosion. GB type does not play a significant role in determining TGCISCC cracking behavior nor susceptibility. TGCISCC crack behaviors at GBs are discussed in the context of the competition between mechanical, crystallographic, and corrosion factors.

Nanoindentation Investigation of Chloride-Induced Stress Corrosion Crack Propagation in an Austenitic Stainless Steel Weld

“…Moreover, the cracks appear to propagate along grains having alternating high and low mechanical hardness. This behavior is consistent with previously reported observations that crystallographic hardness-namely, Schmid (m) and Taylor (M) factor mismatch-control the crack propagation tendency in 304L stainless steel welds [27]. Specifically, our previous work showed that cracks tend to propagate either from crystallographically hard to crystallographically soft grains (i.e., high m, low M grains to low m, high M grains), or vice versa.…”

“…The bent coupon was sectioned by diamond saw into a smaller piece for ease of metallographic polishing; the section piece contained a cross-section of the weld, heat-affected zone (HAZ), and base metal, as represented by the blue dashed lines in Figure 1c. From our earlier study [27], the HAZ was found to be most susceptible to CISCC, and thus, this study focused only on the HAZ. The sectioned piece was polished following standard metallurgical sample preparation processes [50] and finished with 12 h of vibratory polishing.…”

“…Thus, the chlorine-rich corrosive environment on the canister surface, combined with the residual tensile stress from fabrication, makes the weldment region of nuclear waste storage canisters highly susceptible to TGCISCC. Recently, crystallographic and mechanical factors, i.e., the Schmid factor and Taylor factor, have been found to play a significant role in determining TGCISCC behavior [27,28]. Specifically, the mismatch of the Schmid factor and Taylor factor between adjacent grain pairs controls whether the crack will continue to propagate or will arrest at a GB.…”

“…SCC is commonly characterized using techniques such as scanning electron microscopy (SEM) fractography [29], SEM electron backscatter diffraction (EBSD) [5,27], focused ion beam [30], analytical transmission electron microscopy [31], atom-probe tomography [32], 3D X-ray tomography [33,34], and atomic force microscopy [35]. Meanwhile, nanoindentation has been shown to be a versatile tool for evaluating the mechanical responses of nuclear materials [36][37][38][39][40][41][42][43][44][45][46][47].…”

Influence of Nonuniform Microstructure on High‐Cycle Fatigue Properties of the Electron‐Beam‐Welded Joint of High‐Strength Steel

“…Grains with a high Taylor factor are more resistant to plastic deformation than those with a low Taylor factor, making crack deflection or termination easy to occur when there is a large Taylor factor mismatch between adjacent grains. [ 26 ] In Figure 11b, grain I, with a high Taylor factor (3.6), behaves as a “hard” grain, while grain II, with a low Taylor factor (2.5), behaves as a “soft” grain. Due to the large Taylor factor mismatch (1.1) between these two grains, cracks can hardly pass through the grain boundary of the “hard” grain (grain I), resulting in crack deflection.…”