This study explores the application of Electron-Beam Welding (EBW) for joining Laser Powder-Bed-Fused Inconel 718 (L-PBF IN718) superalloy. Three different levels of electron beam speed and beam current were explored to give nine different electron beam heat inputs for experimentation. To define the weld characteristics microhardness, tensile, and fractography analysis using scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were conducted. Typical nail-shaped weld geometry was observed with penetration depth proportional to heat input. Most welded samples exceeded the yield strength (600MPa) and tensile strength (920MPa) requirements from the ASTM F3055 specifications for additively manufactured IN718, however, the specimens did not meet the ductility requirements (27%). Brittleness of the weld was attributed to the presence of brittle secondary phases in the weld matrix, and unfused metal powder of adjacent L-PBF layers. Post-processing heat treatments were recommended to improve the weld quality while improving the ductility of EBW joints.
This paper explores the feasibility of welding Inconel 718 (IN718) and compares the quality of electron beam welded samples produced by rolling and laser-based powder bed fused (L-PBF). Electron beam heat input, varying in the range 175-300 J/mm, was the main parameter in welding. Microhardness, tensile properties, and fractography study using both optical and scanning electron microscopy were employed to analyze and compare the quality of the welded samples. Energy dispersive x-ray analysis was used to identify chemical compositions of different phases on the fractured surfaces. Large voids were observed at high heat inputs (≥ 213 J/mm). Excellent weld penetration was obtained and was proportional to the beam heat input. Both yield and tensile strength of the welded L-PBF'ed materials exceeded those of rolled materials and met the minimum requirement from ASTM speci cation; however, the ductility of welded L-PBF'ed material did not. The brittleness of these L-PBF'ed materials came from the brittle Laves phase and Al-Ti-O compounds in the microstructure and nonoptimal L-PBF parameters. These drawbacks can be further reduced by adjusting the L-PBF parameters and suitable post-processing techniques before electron beam welding.
This paper explores the feasibility of welding Inconel 718 (IN718) and compares the quality of electron beam welded samples produced by rolling and laser-based powder bed fused (L-PBF). Electron beam heat input, varying in the range 175-300 J/mm, was the main parameter in welding. Microhardness, tensile properties, and fractography study using both optical and scanning electron microscopy were employed to analyze and compare the quality of the welded samples. Energy dispersive x-ray analysis was used to identify chemical compositions of different phases on the fractured surfaces. Large voids were observed at high heat inputs (≥ 213 J/mm). Excellent weld penetration was obtained and was proportional to the beam heat input. Both yield and tensile strength of the welded L-PBF’ed materials exceeded those of rolled materials and met the minimum requirement from ASTM specification; however, the ductility of welded L-PBF’ed material did not. The brittleness of these L-PBF’ed materials came from the brittle Laves phase and Al-Ti-O compounds in the microstructure and non-optimal L-PBF parameters. These drawbacks can be further reduced by adjusting the L-PBF parameters and suitable post-processing techniques before electron beam welding.
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