Abstract Spark Plasma Welding (SPW) is among the most advanced methods for joining dissimilar materials. This process enables precise control over atomic diffusion, phase transformation, an‎d grain boundary modification, making it suitable for the fabrication of critical components. The joining of dissimilar materials, such as low-carbon 316 stainless steel an‎d Inconel 718 superalloy, presents significant challenges in the production of components exposed to high temperatures an‎d corrosive environments in aerospace, marine, energy, an‎d petrochemical industries. The joining of these alloys by conventional fusion welding techniques, such as Gas Tungsten Arc Welding (GTAW), is often hindered by the formation of brittle intermetallic phases, heat-induced cracking, an‎d chemical segregation due to considerable differences in chemical composition, thermal expansion coefficients, an‎d alloy element diffusivities. Fusion welding methods cause extensive melting, rapid cooling rates, an‎d severe microstructural heterogeneity; consequently, a significant accumulation of niobium an‎d titanium at elevated temperatures leads to the formation of compounds such as Fe₂Nb, Ni₃Nb, an‎d unstable brittle carbides, severely reducing the tensile strength, bending resistance, impact toughness, an‎d ductility of the joint—rendering the joining of such alloys practically impossible by these processes.Given all these considerations, solid-state welding processes offer the best solution for achieving this joint. Although various solid-state techniques like diffusion bonding, friction welding, an‎d explosive welding have been previously examined, they have shown limited success. Spark Plasma Welding, by generating pulsed electrical discharge an‎d simultaneous pressure, facilitates joining in a quasi-solid-state regime without full melting of the joint area.The present study aims to investigate the microstructure an‎d mechanical properties of the joint between low-carbon 316 stainless steel an‎d Inconel 718 using Spark Plasma Welding. The joining process was studied at temperatures ranging from 800 to 1000 °C, pressures of 40 to 60 MPa, an‎d process times of 5 to 10 minutes. The resulting joint microstructure was characterized by optical microscopy, an‎d grain boundaries an‎d structure were assessed. For detailed analysis of intermetallic phases an‎d reaction layers at the joint interface, X-ray diffraction (XRD) was employed for phase identification, an‎d scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM/EDS) was used to determine layer morphology an‎d thickness. Analysis revealed that the thickness of reaction layers increased with higher process temperatures, an‎d distinctive intermetallic phases with notable continuity were observed at the interface. At 900 °C, a continuous Fe-Ni intermetallic phase formed at the joint boundary. Microhardness at the interface was measured at the aforementioned temperatures. Tensile an‎d bending strengths of the joint were eva‎luated at 850, 900, an‎d 950 °C, yielding maximum tensile strength of approximately 960 MPa an‎d bending strength of 19 MPa at 900 °C. Fracture surfaces were also examined using scanning electron microscopy. Keywords: Spark Plasma Welding, Inconel 718, Low-Carbon 316 Stainless Steel, Mechanical Properties, Microstructure, Dissimilar Joint.

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محمدحسين مصلي‌نژاد , محمدرضا طرقي نژاد