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Analysis of helium used as protective gas in Laser Metal Deposition of Ti6Al4V highly reactive material
摘要： Laser Material Deposition (LMD) is an additive manufacturing near-net-shape process. Metal powder particles are molten by means of a laser heat source and added to a substrate creating geometries. This technology offers the possibility of generating coatings, repairing damaged high-added-value parts, and manufacturing components with complex 3D geometries. Many industrial sectors, including aerospace and die and mold industries, are interested in this process due to its capabilities and the wide range of materials that can be used with it. Previous works aimed to develop a protective gas module to be able to process highly reactive materials without the necessity of a complete inert atmosphere inside the machine. Additionally, the influence of a mixture of argon and helium on the LMD process for other non-highly reactive alloys was evaluated. Hence, the present work aims to broaden the understanding of how the combination of these two factors may affect the LMD process, combining these previous studies and evaluating the phenomenon for a highly reactive alloy like Ti6Al4V. The study involves the melt-pool temperature measurement and characterization of the deposited clads variating not only the composition of the protective gas but also the flow rates.
关键词： LMD,Ti6Al4V,Helium,Titanium,Shielding gas,protective atmosphere,He,Laser Metal Deposition,Argon,Ar
更新于2025-09-23 15:21:01
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Contamination of Coupling Glass and Performance Evaluation of Protective System in Vacuum Laser Beam Welding
摘要： Vacuum laser beam welding enables deeper penetration depth and welding stability than atmospheric pressure laser welding. However, contaminated coupling glass caused by welding fumes in the vacuum space reduces laser transmittance, leading to inconsistent penetration depth. Therefore, a well-designed protective system is indispensable. Before designing the protective system, the contamination phenomenon was quanti?ed and represented by a contamination index, based on the coupling glass transmittance. The contamination index and penetration depth behavior were determined to be inversely proportional. A cylindrical protective system with a shielding gas supply was proposed and tested. The shielding gas jet provides pressure-driven contaminant suppression and gas momentum-driven contaminant dispersion. The in?uence of the shielding gas ?ow rate and gas nozzle diameter on the performance of the protective system was evaluated. When the shielding gas ?ow was 2.0 L/min or higher, the pressure-driven contaminant suppression dominated for all nozzle diameters. When the shielding gas ?ow was 1.0 L/min or lower, gas momentum-driven contaminant dispersion was observed. A correlation between the gas nozzle diameter and the contamination index was determined. It was con?rmed that contamination can be controlled by selecting the proper gas ?ow rate and supply nozzle diameter.
关键词： welding consistency,coupling glass,shielding gas,laser welding,vacuum,protective system,contamination
更新于2025-09-16 10:30:52
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Effect of helium-argon shielding gas in laser-metal inert-gas hybrid welded-brazed Al/steel dissimilar joint
摘要： Laser-metal inert-gas welding hybrid welding was applied to dissimilar butt joining of 304 stainless steel and 6063 aluminum alloy using three different shielding gas: 100% argon, 25% helium + 75% argon, and 50% helium + 50% argon. The influence of helium–argon shielding gas on the weld appearance and interfacial intermetallics layer of Al/stainless steel welding-brazing joint was discussed. The addition of helium can shrink arc, suppress laser plasma, and increase the stability of the droplet transfer process. Helium could not change the composition of the interface layer, which consists of θ-Fe(Al, Si)3 layer and τ5-Al7.2Fe1.8Si layer in the top, middle, and bottom regions of the joints. However, the interfacial intermetallics layer becomes thinner and the morphology was more uniform as the helium content changed from 0% to 50%. By analyzing the tensile fracture, it was found that the thicker θ-Fe(Al, Si)3 easily caused the fracture at the interface layer when using 100% argon. The highest tensile strength and the best ductility can be obtained by using 50% helium + 50% argon compared with that of joints obtained with 100% argon and 25% helium + 75% argon. Compared with joints welded in the pure argon atmosphere, the strength and ductility of joints increased by 18.4% and 191%, respectively.
关键词： laser-MIG hybrid welding-brazing,microstructure,composition of shielding gas,dissimilar materials
更新于2025-09-12 10:27:22