PSI - Issue 68

Mahmoud Khedr et al. / Procedia Structural Integrity 68 (2025) 1017–1023 Mahmoud Khedr / Structural Integrity Procedia 00 (2025) 000–000

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Figure 1. Microstructure of base metals; (a) LCS; (b) MMn-SS; (c) NiCr-SS.

Figure 2. Microstructure of FZs; (a) LCS/MMn–SS; (b) LCS/NiCr-SS.

Figure 3 shows the optical micrographs of dissimilar welding of LCS/MMn-SS and LCS/NiCr-SS, respectively. The HAZ was significantly influenced by the value of the heat input during the welding process. The widths of the HAZ of LCS are higher than the widths of HAZ of MMn-SS and NiCr-SS because of volumetric heat capacities of LCS are lower than MMn-SS and NiCr-SS. 3.2. Hardness Measurements Hardness measurements were carried out in the transverse direction which is parallel to the base plate surface from the center of the weld metal towards the fusion boundary, HAZ, and BM for both sides of LCS/MMn-SS and LCS/NiCr-SS. Figure 4 represents the hardness measurement results along the BMs, heat-affected zones, and FZ of LCS/MMn-SS and LCS/NiCr-SS. The average hardness values of LCS, MMn-SS, and NiCr-SS are 125.1±3, 268.9±7, and 181.3±4 VH, respectively. The hardness values of LCS/MMn-SS and LCS/NiCr-SS at the center of the FZ recorded 166.8 and 155.5 VH, respectively. Moreover, the hardness values of HAZs for both sides of MMn-SS and NiCr-SS near the fusion boundary were lower than the HAZs near the BMs due to the grain coarsening presence in the adjacent HAZ to the fusion boundary. It is observed that the welded metals have lower hardness values than the MMn-SS and NiCr-SS. These decreases in the hardness values are attributed to the significant grain coarsening, and thermal softening effects alongside the promoted delta ferrite in the weld metal formed during the solidification stage in this zone.