Evaluation of crevice stress corrosion cracking of austenitic stainless steels in oxygenated high temperature water = 산소가 첨가된 고온 수화학 환경에서 오스테나이트계 스테인리스강의 틈새 응력부식균열 평가

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Socket welds are commonly used in small bore pipes to connect valves, elbows, and flanges in various piping systems in pressurized water reactors (PWRs). During the operation, these welds are subjected to high cyclic fatigue, which may result in fatigue cracking and leakage of primary system coolant. For a temporary measure, an installation of a clamping device surrounding the damaged area is being considered to retain the leakage until the permanent repair by weld overlay or replacement of damaged components. Once clamps are installed, crevices and local tensile stresses would be developed in the bolted region. Therefore, susceptibility to stress corrosion cracking (SCC) of the clamp materials such as types 304, and 316 austenitic stainless steels should be properly evaluated. In this study, crevice bent beam (CBB) tests were performed in simulated pressurized water environment containing up to 8ppm of dissolved oxygen to simulate the anticipated conditions in clamping devices where the trapped air in the clamp could be dissolved into the leaked water. According to the analysis, the results shows high susceptibility to SCC in case of SS304 compared to SS316 that shows efficient resistance even in the oxygenated PWR water. Martensite transformation was found to be a main factor to SCC initiation and propagation in SS304 which showed high susceptibility to such a transformation. The crack propagated both IGSCC and TGSCC, where most of TG cracks branched from IG cracks were associated with the presence of martensites which could have been formed under tensile strain.
Advisors
Jang, Chang Heuiresearcher장창희researcher
Description
한국과학기술원 :원자력및양자공학과,
Publisher
한국과학기술원
Issue Date
2018
Identifier
325007
Language
eng
Description

학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2018.8,[vii, 56 p. :]

Keywords

Austenitic stainless steel▼aoxygenated PWR water▼acrevice beam bent (CBB)▼amartensites▼aintergranular stress corrosion cracking (IGSCC)▼atransgranular stress corrosion cracking (TGSCC); 오스테나이트계 스테인리스강; 고온 수화학 환경; 틈새굽힘보; 마르텐사이트; 응력부식균열

URI
http://hdl.handle.net/10203/266575
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=828545&flag=dissertation
Appears in Collection
NE-Theses_Master(석사논문)
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