In recent time, solid state crack repair techniques in spent nuclear fuel dry storage canisters (SNF-DSC) have garnered significant interest. Plates of austenitic stainless steels are usually arc welded to fabricate the cylindrical canisters which are prone to chloride-induced stress corrosion cracking. Friction stir welding (FSW) is considered to be a potential candidate for damage repair. In this work, electrical discharge machining was used to simulate cracks in 304L stainless steel plates of 12.7 mm thickness. Subsequently, isothermal FSW was carried out at two different temperatures (725 and 825°C) in order to repair the simulated crack. Microstructure-mechanical property correlations in FSWed plates were studied in detail. Significant grain refinement observed in the stir zone (SZ) was attributed to dynamic recrystallization occurring during FSW. A comparison of Vickers microhardness showed higher hardness and homogeneity in the 725°C SZ than its 825°C counterpart. The fraction of Σ3 boundary is found to be low in the SZ as compared to base metal (BM). Yield strength of the joints was found to be approximately 100 MPa higher than that of the BM accompanied by a drop in ductility by a factor of 2. Residual stress profile across 825°C weld was measured using x-ray diffraction.

Friction Stir Spot Welding (FSSW) is a solid-state joining technique widely applied to high conductive metals. In this paper, the effects of FSSW parameters, namely, rotational speed (N), plunging rate (V) and dwell time (DT) on the joint fracture mode and fractured surface morphology were investigated using scanning electron microscopy (SEM). The effect of the abovementioned welding parameters on the microhardness profile along the sheets’ interface was also investigated to gain insight into the strength of the joint and the width of the bonding ligament. Two conditions were considered for each parameter 1200 rpm and 900 rpm for N, 60 mm/min and 20 mm/min for V, 4 and 2 seconds for DT. The welding condition 1200 rpm rotational speed, 20 mm/min plunging rate and 2 seconds dwell time showed a wider bonding ligament, relatively higher elongation, higher tensile failure load, and greater microhardness on the sheets’ interface. Dimple surface morphology (DSM) with regular dimples along the stir zone was also observed at the abovementioned set of process parameters.