# Oxidation-Reduction of Ti-6 Al-4V in Direct Energy Deposition Subject to Minimum Argon Consumption
## 6 Conclusions  
This study focuses on the additive manufacturing of Ti-6 Al-4V using a direct energy deposition (DED) process with a coaxial deposition nozzle in an open-air environment. In this study, a prototype of a new nozzle attachment system was developed to provide conformal shielding to reduce the oxygen concentration in critical areas by a minimal amount of shield gas usage. The critical shielding area was divided into eight segments, with each segment corresponding to one attachment in the nozzle attachment system. This design ensures that shielding gas is supplied only to the specific attachment required for the deposition path, eliminating unnecessary gas usage across all eight attachments simultaneously.  
Due to the unavailability of the DMG MORI coaxial AM machine, a 3D-printed nozzle was used to facilitate the conformal shielding nozzle attachment system. An oxygen sensor was used to monitor the oxygen concentration using the attachment system. Four different flow rates were tested to determine the optimal shield gas flow rate at three different locations under the attachment. This study also evaluated the time required to establish a safe shielding environment during the deposition process.  
A shield gas flow rate of 25 SCFH was chosen to be used in this study. However, due to the extended time required to establish optimal shielding conditions with a 25 SCFH flow rate, a high activation flow rate of 60 SCFH per attachment was introduced for 2.1 s during the initial activation phase of the attachment. Additionally, to further minimize the time required to create an optimal shielding environment, a constant baseline flow rate of 5 SCFH was maintained in all attachments at all times. This approach ensured the rapid establishment of effective shielding conditions while optimizing gas consumption.  
Overall, the system uses 65 SCFH of shield gas for the deposition process in the DED process. Compared with other shielding procedures that use 150-250 L/min (300-550 SCFH), with this new system, the shield gas consumption was reduced by 85%.  
B.R.: Conceptualization, Methodology, Validation, Investigation, Data curation, Writing-original draft preparation; P.R.: Writing--original draft preparation, writing--reviewing and editing; T.S.--Formal Analysis, Supervision, Project Administration; F.L.--Funding Acquisition, Supervision, Project administration. All authors have read and agreed to the published version of the manuscript.  
This study was also supported by the Center for Aerospace Manufacturing Technologies (CAMT)/Boeing, the Intelligent Systems Center (ISC), and the Material Research Center (MRC) at Missouri S&T. Their financial support is greatly appreciated.  
Not Applicable.  
The original contributions presented in this study are included in the article.  
This study was supported by the Center for Aerospace Manufacturing Technologies (CAMT)/Boeing, the Intelligent Systems Center (ISC), and the Material Research Center (MRC) at Missouri S&T. Their financial support is greatly appreciated.  
Author [PERSON] was employed by the company Product Innovation and Engineering LLC. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.