Most of the existing batches of spent nuclear fuel (SNF) dry storage canisters (DSCs) are made up of 304L austenitic stainless steel. The major concern with these welded austenitic stainless steel canisters is the occurrence of pitting and stress corrosion cracking (SCC) due to a combination of deliquescence of chloride-rich salts deposited on the warm outer canister surfaces under certain conditions of humidity near marine environments and tensile residual stresses present in the weldments. For continuous utilization of these SNF DSCs around the world, employing cost-effective and efficient repairing and mitigating methods is of paramount importance. In this investigation, the effects of laser shock peening (LSP), with and without ablative coating, and ultrasonic nanocrystalline surface modification (UNSM) on the corrosion resistance of 304L stainless steel (SS) weldments and base metal was studied using DLEPR to evaluate the degree of sensitization (DOS) and susceptibility to intergranular attack (IGA). In addition, boiling MgCl~2~ test was also conducted to study the SCC resistance before and after surface treatment. Characterization of the microstructure was achieved using SEM, TEM, EBSD and XRD. Residual stress depth profiling by XRD was utilized to understand the depth of effect from the mechanical surface treatments. Current results are indicating a notable impact of both LSP and UNSM on reducing the susceptibility of 304L SS under corrosive conditions. The specific complexities as effected by the varying LSP and UNSM treatments (residual stress, deformation-induced martensite, etc.) and their aforementioned effects will be presented and discussed.


A Study of the Effects of Laser Shock Peening and Ultrasonic Nanocrystalline Surface Modification on the Susceptibility of 304l Stainless Steel to Intergranular Corrosion

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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