OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Fig. 9 shows the distribution of chemical elements along a line positioned perpendicular to the transition zone in the case of nickel alloy deposition onto steel. In all cases, a wide transition zone is observed. As can be seen, under processing mode 1 (1,000 W, 35 mm/s), the concentrations of iron and nickel equilibrate within 50 μm from the visible fusion boundary between the dissimilar materials, already within the first deposited layer (Fig. 9, a). Under mode 2 (1,250 W, 25 mm/s), the concentrations of nickel and iron begin to equalize at a distance of 500–600 μm from the visible fusion line (Fig. 9, b). This region corresponds approximately to the boundary of the second deposited layer of the nickel alloy. In contrast, under mode 3 (1,500 W, 15 mm/s), the concentration equalization occurs significantly beyond the second nickel alloy layer and corresponds to a distance of 800–900 μm from the visible fusion boundary between the dissimilar materials (Fig. 9, c). In these transition regions, the nickel concentration is lower than that of the original nickel alloy and ranges between 35–45 wt. %. Below the visible fusion boundary, the steel regions retain their original composition, with a slightly elevated nickel content of up to 11 wt. %. a b c Fig. 9. Energy-dispersive X-ray spectroscopy (EDS) analysis results for the 316L stainless steel – Inconel 625 joint: a – mode 1; b – mode 2; c – mode 3 According to quantitative energy-dispersive X-ray spectroscopy (EDS) analysis, the zones of mechanical mixing of steel into the nickel alloy are characterized by reduced iron content and increased nickel content (Table 3). An increase in both distance from the fusion boundary and laser power promotes higher nickel content in these regions. During the deposition of steel onto the nickel-based alloy, a wide transition zone and numerous regions of mechanical mixing were also observed (Fig. 10). The visible fusion boundary between the nickel alloy and steel is well-defined under the first two processing modes. Under mode 1 (1,000 W, 35 mm/s), the concentrations of iron and nickel begin to equilibrate within the first deposited layer of the nickel alloy at a distance of 300–400 μm from the visible fusion line, with the iron concentration starting to gradually increase within 50–100 μm beyond that point. Under mode 2 (1,250 W, 25 mm/s), the equalization of iron and nickel concentrations occurs at a distance of 600–700 μm from the visible fusion boundary between the dissimilar materials, corresponding to the level of the second deposited steel layer. Under mode 3 (1,500 W, 15 mm/s), the visible interface between the nickel alloy and steel becomes more diffuse, and the iron concentration exceeds that of nickel at the boundary of the second deposited steel layer, similarly to mode 2. In this region, the iron concentration within the second deposited steel layer is in the range of 40–45 wt. %. In the regions of the nickel alloy located below the visible fusion boundary, the chemical composition under mode 1 corresponds to that of the original alloy. However, for modes 2 and 3, an elevated iron content and a slightly reduced nickel content were observed – 9 wt. % and 52 wt. %, respectively. The composition of the mechanical mixing zones, where nickel alloy is incorporated into the steel matrix, is characterized by an increased iron content and a correspondingly reduced nickel content compared to the original Inconel 625 alloy (Table 4). The varying ratio of chromium and nickel equivalents indicates the formation of zones with different phase compositions. According to established models of phase formation during welding of dissimilar
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