PSI - Issue 79

Saveria Spiller et al. / Procedia Structural Integrity 79 (2026) 176–181

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prevent the need for replacement (AL-Nafeay et al., 2021; Henderson et al., 2004). Typical welding defects are a lack of penetration, welding cracks, porosity, extended heat-affected zone (HAZ), and others (Schnell et al., 2011). Laser Beam Welding (LBW) is a high-energy density welding technique that, unlike conventional welding processes, induces a reduced heat input on the plates to be welded. This results in a narrow fusion zone, limited HAZ, minimal distortion, and residual stresses in the joints, also preventing elements segregation in the FZ (Patterson et al., 2021). For these reasons, LBW is often claimed to be more appropriate than conventional welding processes to increase the quality of the joint obtained, even in the absence of filler material. Although a proper tuning of the process parameters is paramount to enhance the abovementioned positive characteristics of the joints, the chemical composition and the microstructure of the parent material (i.e., the furniture state) play a crucial role in the appearance of welding defects (Donnini et al., 2025). The weldability of Inconel 625 (IN625) is usually favored by the fact that it is a solution-strengthened alloy with a limited amount of Al and Ti (Sekhar et al., 2002). Indeed, in precipitation-hardened alloys, these are the elements that tend to form precipitation phases that might have a detrimental effect on the welding process itself. These phases, named γ ’ and γ ’’, decrease the ability of the material to accommodate residual stresses and tend to create regions with eutectic composition at the grain boundaries prone to liquate during the welding process. On the contrary, IN625 in wrought and cast conditions is mainly composed of the γ ’ phase. The precipitation of γ ’’ is possible only through high-temperature heat treatments (Sundararaman et al., 1985). The weldability of IN625 produced via Additive Manufacturing (AM) has been rarely studied (Talei et al., 2025). However, AM processes such as Laser Power Bed Fusion (L-PPB) induce a peculiar microstructure on the components with a high degree of anisotropy, related to the unique thermal history of the parts. Considering the benefits associated with additive manufacturing, it is of paramount interest to investigate whether the weldability of the alloy is preserved in the case of an additively fabrication process of the parent material.

Nomenclature AM

Additive Manufacturing Building Direction

BD BoP

Bead on Plate Fusion Zone

FZ

HAZ Heat Affected Zone LBW Laser Beam Welding L-PBF Laser Power Bed Fusion PM Parent Material WD Welding Direction

2. Materials and Methods One Bead on Plate (BoP) was obtained on an IN625 plate produced via L-PBF. The plate was built in a horizontal layout as depicted in Fig. 1, with the main process parameters adopted being laser power 260 W, scanning speed 960 mm/s, and layer thickness 0.04 mm. The chemical composition of the IN625 powder that was used is reported in Table 1. The laser welding parameters that were chosen are reported in Table 2. The power mode was modulated with a ratio of R=P min /P max =0.6. The average power is 1920 W, and the welding speed is 25 mm/s. A metallographic section was extracted from the cross-section of the plate and prepared following standard metallurgical preparation. The cross-sections of the welds were observed with the optical microscope Leica® CTR6 and the scanning electron microscope (SEM) FEI® Quanta 250. Microstructural and chemical composition analyses were carried out using the energy dispersive spectroscopy (EDS, Thermofisher® UltraDry X-Ray detector) and the electron backscattered diffraction (EBSD, EDAX® Hikari camera). To highlight the fusion zones, the specimens were etched using the solution composed of 70 ml H 3 PO 4 and 30 ml water. Microhardness profiles were produced on the fusion zone’s cross-sections using the indenter FutureTech® microhardness tester FM810 equipped with a Vickers’ indenter and loaded with 500g.