Materials Science and Engineering A 452–453 (2007) 652–656 Validation of a novel approach to determination of threshold for stress corrosion cracking (K ISCC ) R.K. Singh Raman a,b,∗ , R. Rihan a , R.N. Ibrahim a a Department of Mechanical Engineering, Monash University, Vic. 3800, Australia b Department of Chemical Engineering, Monash University, Vic. 3800, Australia Received 19 June 2006; accepted 2 November 2006 Abstract Determination of threshold stress intensity for stress corrosion cracking (K ISCC ), using circumferential notch tensile (CNT) specimens has been developed recently. This has also been claimed to be a novel and considerably cost-advantageous approach in comparison with the traditional methods, viz., compact tension (CT) and double cantilever beam (DCB) techniques for determination of K ISCC . However, the limited first K ISCC data, generated using CNT specimens have been queried for the lack of their comparison with the data generated by other techniques. This work presented here provides the first comparative results and validation for use of the novel CNT testing for generation of K ISCC data. © 2006 Elsevier B.V. All rights reserved. Keywords: Circumferential notch tensile (CNT) testing; Stress corrosion cracking (SCC); Threshold stress intensity for SCC (K ISCC ) 1. Introduction Stress corrosion cracking (SCC) is the premature cracking of materials under the synergistic action of a tensile stress and corrosive medium [1]. The features that make SCC possibly the most dangerous among the corrosion-assisted failures, as well as a serious consideration in material selection and design of equipment operating in corrosive environments include: (a) given the required combination of stress and environment, stress corrosion cracks may propagate undetected to leaks or even to sudden catastrophic failures, (b) environments that are only mildly corrosive may cause severe SCC and (c) sometimes, the alloy may virtually appear unattacked over most of its sur- face and only a few fine and localized cracks may propagate undetected to failure [2]. A great proportion of failures of indus- trial components operating in corrosive environment occur by SCC. Hence, a reliable, cost-effective and rapid characteriza- tion of SCC susceptibility of in-service and failed components is highly attractive for plant operation and maintenance. Life extension/prediction of components exposed to in-service cor- rosive environments often involves assessment of susceptibility ∗ Corresponding author at: Department of Mechanical Engineering, Monash University, Vic. 3800, Australia. Tel.: +61 3 9905 3671; fax: +61 3 9905 1825. E-mail address: raman.singh@eng.monash.edu.au (R.K. Singh Raman). of existing cracks to environment-assisted propagation. Deter- mination of the critical value of stress intensity factor (K I ) necessary for propagation of an existing crack is a critical mate- rial selection criterion [3]. For an alloy–environment system conducive to SCC, determination of the threshold stress inten- sity with the influence of environment at the crack tip (i.e., K ISCC ) is essential for any mechanical engineering design. K ISCC has traditionally been determined using bulky specimens (viz., compact tension (CT) and double cantilever beam (DCB) test specimens [4,5]), in order for the specimens to comply with the requirements of valid plain strain condition. Such spec- imens are generally expensive to manufacture/test, requiring prohibitively long testing time and relatively expensive loading system for applying desired loads. Therefore, a rapid, accurate and cost-effective determination of K ISCC is of immense interest to prudent design engineers. Circumferential notch tensile (CNT) specimens are one of the smallest possible specimens that have been used for generation of K ISCC data [6–8]. Potential advantages of smallness of the CNT specimens are likely to include a considerable reduction in testing costs because of requirement of small amounts of testing material and small loading devices for achieving desired stress intensities. Recently, CNT technique has been successfully used for determination of K ISCC of spheroidal graphite (SG) cast iron in hot caustic solutions [6,8]. Choice of SG cast iron as the first test material was based on the fact that this is an inherently brittle 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.11.067