A Simple Approach to the Determination of Threshold Stress Intensity for Stress Corrosion Cracking ( K ISCC ) and Crack
- PDF / 952,791 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 255 Views
INTRODUCTION
STRESS corrosion cracking (SCC), the brittle failure of otherwise ductile metallic materials under a simultaneous action of stress and corrosive environment, is an ongoing concern in numerous industries. The threshold stress intensity factor (KISCC) is the most common parameter for design and life prediction of stressed engineering components exposed to corrosive environments. Austenitic stainless steels are the most widely used corrosion-resistant alloys. However, when these steels having sufficient carbon contents are heated for sufficient durations at 542 K to 977 K (415 C to 850 C), chromium-rich carbide precipitates (M23C6) form along the grain boundaries, and as a result, the areas adjacent to the grain boundaries suffer depletion of free Cr (this phenomenon is known as sensitization[1]). Sensitized grain boundaries are known to provide easy propagation path for SCC of austenitic stainless steels in chloride solutions.[2,3] The areas adjacent to the weld pool, i.e., heat-affected zone (HAZ), of austenitic stainless steel weldments are susceptible to sensitization and, hence, are more susceptible to SCC. Therefore, chloride SCC of sensitized stainless steels has been investigated considerably.[4–7] However, the determination of KISCC of sensitized R.K. SINGH RAMAN, Professor, is with the Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC 3800, Australia, and also with the Department of Chemical Engineering, Monash University. Contact e-mail: raman. [email protected] SARVESH PAL, formerly PhD Student with the Department of Mechanical and Aerospace Engineering, Monash University, is now Postdoctoral Fellow with the School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4800, Australia. Manuscript submitted November 7, 2010. Article published online April 21, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
stainless steels has invariably necessitated using bulky specimens of various geometries (viz. double cantilever beam (DCB), compact tension (CT), and wedge opening loading (WOL)[4,7–12]), in order for the specimens to satisfy the valid plane strain conditions, which is a mandatory condition for application of linear elastic fracture mechanics (LEFM). Nevertheless, the life prediction of in-service welded components would necessitate determination of KISCC of the most susceptible regions, i.e., HAZ and weld metal, which are narrow, and hence prohibit the use of any bulky specimens (namely, DCB, CT, or WOL). For another critical reason, these traditional techniques are not suitable even for testing fabricated specimens of weld metal or HAZ; i.e., because of the geometrical limitations at the notch and crack tip, it may be difficult to control the crack propagation in one plane. As a result, the crack may propagate out of the zone of interest (as illustrated in Figure 1). The complications arising due to the narrowness of the HAZ or weld metal may be circumvented by simulation of the HAZ microstructure over a wide area using a precise th
Data Loading...
