# Oxidation-Reduction of Ti-6 Al-4V in Direct Energy Deposition Subject to Minimum Argon Consumption
## 5 Discussion
### High Activation Flow Rate and Constant Argon Flow in the Attachments  
To rapidly reduce the oxygen concentration during deposition, a constant baseline flow of 5 SCFH was maintained in all the attachments. During activation, an additional flow rate of 60 SCFH was provided to bring down the oxygen concentration in the critical area. It was observed that it took 1.4 s for the oxygen concentration to get to 0 PPM at locations B and C and 2.1 s at location A using this additional flow of 60 SCFH. From the graph in Figure 13, it can be observed that using a 60 SCFH flow rate alone achieves a 0 PPM oxygen concentration within 4.9 s from an initial level of 200,000 PPM. However, by combining the baseline flow rate of 5 SCFH in each attachment, the time was reduced by half. This is because the increased Ar gas around the AM nozzle created an argon shield, acting as a barrier for O2 molecules to enter. Providing a constant supply of 5 SCFH significantly reduced the oxidation in the critical areas, followed by 60 SCFH of shielding gas by the required attachment. Considering location A in the graph in Figure 15, the time required to keep the activation flow is determined to be 2.1 s. Overall, the system requires a 25 SCFH in any given attachment during deposition, along with a 5 SCFH in each of the eight attachments, totaling a flow rate of 65 SCFH for steady-state deposition. The additional requirement of 60 SCFH, activated for a very short duration during attachment transitions, can be considered negligible in the overall gas consumption calculation. Compared with other means of shield gas usage of  
Figure 14: Variation in the oxygen concentration with flow rates of 50 and 60 SCFH. 423 SCFH (200 L/min) for additive manufacturing, this system reduced the consumption by 85%. The recent advancements in shielding methods for Ti-6 Al-4V in direct energy deposition (DED) processes have been explored in the literature. [PERSON] et al. emphasized the importance of supplementary argon flow for high-quality deposition of Ti-6 AL-4V using a DED process [29]. This study approached shield gas distribution for the deposition process. The attachment system in this paper provides shield gas with greater precision on the substrate compared to [PERSON]'s study, which significantly reduces shield gas usage. [PERSON] et al. and [PERSON] et al., in their studies, were able to provide effective shielding to the substrate but relied on a static system, such as the bath and bag methods [27]. In comparison, the modular design conformal shielding attachment system dynamically adjusts to varieties of additive manufacturing coax nozzles and can produce various shapes of prints. Unlike vacuum-based shielding systems, which restrict the shape and size of the print, this design has open-air applications that do not limit the size of the component. In comparison with traditional shielding methods, where shield gas is provided at 360 degrees across the entire deposition area, this study optimizes the shield gas usage by providing the shield gas directed only on the critical areas, significantly reducing the shield gas usage. Scalability, operational flexibility, and operational costs are key parameters that drive manufacturability at industrial levels. This design offers scalable solutions with reduced operational costs by reduced shield gas usage. This work represents a significant advancement in the field of additive manufacturing, considering the prior work on shielding concepts. The system uses a high activation flow rate of 60 SCFH, which is used to rapidly achieve optimal shielding conditions. This approach significantly reduces the time to bring down the safe oxygen concentration levels during the deposition process. In this nozzle attachment system, a high activation flow rate is only used while transitioning from one attachment to the other. For large-scale and continuous operations, for which the open-air coax nozzle is intended, fewer transitions among attachments will take place.