Oxidation–Reduction of Ti-6Al-4V in Direct Energy Deposition Subject to Minimum Argon Consumption

Ti-6Al-4V is a well-known alloy for its low density and excellent corrosion resistance, making it popular in aerospace, marine, medical, and automotive applications. However, at elevated temperatures, the alloy forms oxides, leading to embrittlement. In additive manufacturing, particularly in the direct energy deposition (DED) process, which involves high temperatures, the alloy experiences oxidation. An inert gas chamber provides shielding during the process but limits the size of the manufactured components, and deposition in a vacuum chamber can alter the chemical composition of the alloy. Local shielding is a technique generally used for such applications, but it uses a high volume of shield gas, contributing to environmental contamination. This study presents a novel approach for the development and preliminary evaluation of a prototype nozzle attachment system for the additive manufacturing (AM) of Ti-6Al-4V using a direct energy deposition (DED) process in an open-air environment system. The system was designed to reduce shield gas consumption by providing conformal shielding in critical areas. This was achieved by dividing the shielding area into eight segments, with each of the eight attachments of the nozzle attachment system selectively activated to supply shield gas only where required. Four different shield gas flow rates of 20, 25, 30, and 35 SCFH were tested at three different locations under the attachment to investigate the optimal flow rate. The results proposed maintaining a baseline flow rate of 5 SCFH in all attachments and employing 60 SCFH during transitions between attachments for rapid shielding. The system maintained oxygen concentration levels below 200 PPM within 2.1 s, with an average gas consumption of 65 SCFH, underlining an 85% reduction compared to other studies. These findings highlight the potential of this system for future implementation and scalability for reactive metal depositions like Ti-6Al-4V in AM using DED processes. This study addresses the need for an effective shielding environment during deposition while minimizing the shield gas consumption. A nozzle attachment system was designed and developed to provide conformal shielding during the deposition process. Key parameters, such as the shielding flow rate, activation time, and shielding range of the nozzle attachments, were investigated. The system successfully delivered shield gas to the critical areas and provided a safe environment for deposition. Argon consumption was reduced by 85% compared to other studies in the same field, with an optimal flow rate of 25 Standard Cubic Feet per Hour (SCFH) of shielding gas used to cover all critical areas in the experiments. The effect of the laminar and turbulent flow of shield gas on the deposition path was also analyzed in this study.