Ordinarily, two parts of the cohesive forces are summarized as the surface energy and the plastic deformation work. It is indicated that the IGSCC of non-sensitized austenitic stainless steel becomes another probably-existing phenomenon, and the corresponding mechanism is necessarily elucidated at length.įurthermore, whether the IGSCC or the TGSCC occurs obviously depends on the cohesive forces between the SCC facets in the cohesive zones. More interestingly, for the type 304 solution-annealed austenitic stainless steel, the SCC cracks nucleated transgranularly at the initial stage, and switched to the IGSCC mode with increasing the crack-tip stress under the constant load 13. These experimental results indicate that the sensitized austenitic stainless steel is susceptible to both the IG- and TGSCC. Subsequently, Sarvesh Pal and Singh Raman 13 also discovered that the IGSCC initiated and propagated with a few accompanying TGSCC phenomena in the type 304 sensitized austenitic stainless steel. At the average stress level of 300 MPa, the IG- and TGSCC of the type 316 sensitized austenitic stainless steel took place in the 133 ☌ and 145 ☌ boiling MgCl 2 solutions, respectively 12. For the type 304 sensitized austenitic stainless steel, the average IGSCC stress level of 300 MPa was higher than the average TGSCC stress level of 200 MPa 11. Alyousif and Nishimura 11, 12 have carried out some constant-load SCC experiments in the sensitized austenitic stainless steel immersed into the boiling MgCl 2 solutions. In particular, since the Cr-depleted grain boundaries in the sensitized austenitic stainless steel heated at 415–850 ☌ act as anodes and dissolve preferentially 10, the localized stress concentrates in the vicinity of the dissolved grain boundaries, and the brittle cleavage is apt to occur on the grain boundary facets at relatively low applied stress levels. To sum up, the non-slipping TGSCC of the type 316L austenitic stainless steel exhibits the same crystallographic features even using the diverse characterizations and analysis techniques, whereas no common understanding of the TGSCC with dislocation slipping has been arrived at until now.Īpart from the TGSCC, the intergranular (IG) SCC is probable to occur in the austenitic stainless steel as well. Thus, it is difficult to distinguish between the ductile fracture and the brittle cleavage.
The two-surface trace analysis has demonstrated that the non-slipping TGSCC advances along cleavage planes in ligaments was simultaneously observed in the same tests 8. Previous experimental results have indicated that the transgranular (TG) SCC fractography is generally river-like and crystallographic in type 316L stainless steel at the elastic stress levels 1, 2, 3, and the TGSCC can also take place in mode I, II and III loaded austenitic stainless steel 4, 5, 6. Brittle rupture of ductile metals, for instance stress corrosion cracking (SCC) of austenitic stainless steel in chloride solutions, usually advances on grain boundaries or crystal planes.
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