Mitigating Stress Corrosion Cracking in Austenitic Stainless Steel Canister Welds Using Peening Techniques
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Authors
John, Merbin
Issue Date
2023
Type
Thesis
Language
Keywords
Austenitic stainless steel , Grain refinement , Peening , Residual compressive stress , stress corrosion cracking , Welding
Alternative Title
Abstract
Austenitic stainless steel (ASS) is an ideal material choice for storing spent nuclear fuels (SNFs) in dry storage canisters (DSCs). However, due to the chloride-rich environments in which they operate, stress corrosion cracking (SCC) failures frequently occur in DSC weld joints manufactured using gas tungsten arc welding (GTAW). To mitigate this issue, the present investigation utilizes various peening techniques to enhance the SCC resistance of DSC weld joints. In this work, the effect of laser-based peening (laser shock peening (LSP), and laser shock surface patterning (LSSP)), and mechanical-based peening (shot peening (SP), and ultrasonic impact peening (UIP)) on SCC resistance of the GTAW’ed ASS were investigated. The strain-induced martensite transformation, residual stress, surface roughness, and microstructure were studied in the weld joints and weld joints subjected to peening and correlated with SCC resistance. All the peening techniques induced grain refinement, enhanced surface properties, and introduced residual compressive stress (RCS) in the subsurface. The synergistic effect of RCS and grain refinement enhanced the SCC resistance of peened weld joints. Among the peened weld joints, UIP’ed weld joints showed superior SCC resistance, followed by SP, LSP, and LSSP. The superior SCC resistance of UIP’ed weld joints is attributed to the absence of strain-induced martensite transformation in the microstructure that was present in all other peened weld joints. The inferior SCC resistance of LSP’ed and LSSP’ed weld joints is attributed to residual tensile stress (RTS) on the surface, which caused crack initiation at an early stage.
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License
Creative Commons Attribution 4.0 United States