Stress corrosion cracking crack path

Fig. 7.90 Effect of stressing direction on the intergranular stress-corrosion crack path in susceptible high-strength aluminum alloy. Dark boundaries are representative of ones favored for cracking for indicated direction of applied stress. Source Ref 97...

V.Y. Gertsman and S.M. Bruemmer, Study of grain boundary character along intergranular stress corrosion crack paths in austenitic alloys, Acta Materialia 49 1589-1598,2001. 

Figure 15.19 shows various crack orientations that can occur in connection and attachment welds. Applied stresses from external loading of these components can add to the residual weld stresses, producing still higher stress loads. This can increase the susceptibility to stress-corrosion cracking and can affect orientation and location of crack paths. 

Stress-corrosion cracking based on active-path corrosion of amorphous alloys has so far only been found when alloys of very low corrosion resistance are corroded under very high applied stresses . However, when the corrosion resistance is sufficiently high, plastic deformation does not affect the passive current density or the pitting potential , and hence amorphous alloys are immune from stress-corrosion cracking. 

Heat treatment may also affect the extent and distribution of internal stresses. These may be eliminated by appropriate annealing treatments which can remove susceptibility to stress-corrosion cracking. This must be explored in any studies of the performance of materials in environments where stress-corrosion cracking is a hazard. In particular cases, stress-relief annealing treatments may result in the appearance of new phases which, while eliminating the stress-corrosion effects, will induce another type of path of attack. This possibility must be kept in mind in assessing the overall benefits of heat treatments applied primarily for stress relief. 

Much earlier in this book (Section 7.10), the point was made that the path and rds for hydrogen evolution divide themselves into those (e.g., H30+-> Hads+H20 2Hads- H2) in which 9H is 1 and those (e.g., H30++ e H20 + H H30+ + Hads + e —> H20 + H2) in which 6 —> 1. The distinction between these mechanisms is important for Fe because of the effect of the value of the coverage with 9 on embrittlement and the related stress corrosion cracking (Section 12.6.5). This is more likely if 9 is larger than when it is small because a large 9 increases the driving force for the permeation of H into the metal. 

E.N. Pugh, J.V. Craig, and W. Montaguer, Factors Influencing the Path of Stress-Corrosion Cracking in Alpha-Phase Copper Alloys Exposed to Aqueous Ammonia Environments, Trans. ASM, Vol 61, 1968, p 468-473... 

Active Path. Since the term stress corrosion cracking implies corrosion, it is not surprising that... 

Figure 19.7. Stress-corrosion cracking of 18-8, type 304 stainless steel exposed to calcium silicate insulation containing 0.02-0.5% chlorides, 100°C (250x). Note that the cracks for this environment start at a pit. An undulating path accounts for disconnected cracks as viewed in one plane [47]. (Copyright ASTM International. Reprinted with permission.)...

Stress corrosion is cracking that develops in sensitive aHoys under tensile stress which is either internally imposed or is a residual after forming, in environments such as the presence of amines and moist ammonia. The crack path can be either intercrystaHine or transcrystaHine, depending on aHoy and environment. Not aH aHoys are susceptible to stress corrosion (31). 

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