## 5 Conclusions and Future Work  
The present study describes an experimental procedure for determining the spatial oxygen concentration of the direct metal deposition process. Furthermore, the influence of the carrier gas volume flow on the shield gas volume flow is presented. Furthermore, a numerical model is developed that considers thermal effects on the resulting oxygen concentration. The results confirm that the nozzle type and gas settings have a noteworthy influence on the oxygen concentration. This can be used to improve the quality of AM parts made from oxidation-critical materials. The experimental results and the simulation led to the following conclusions:  
* The simulation of the oxygen concentration is congruent with the results of the experimental oxygen measurements. Figure 13: Influence of the shield gas chamber on the oxygen concentration for various carrier to shield gas flow ratios. **Top**: Three-jet nozzle. **Bottom**: Coaxial nozzle. * The spatial oxygen concentration of the three-jet nozzle is less pronounced in comparison to the coaxial nozzle. The center of low oxygen concentration follows the nozzle geometry. * The carrier gas volume flow has a greater impact on the oxygen concentration compared to the shield gas volume flow. * The coaxial nozzle is less sensitive to gas ratio variations than the three-jet nozzle. From a carrier gas volume flow to shield gas volume flow ratio of 0.4, the three-jet nozzle leads to high oxygen concentrations. * A shield gas chamber practically eliminates the influence of the gas settings on the present oxygen concentration. In further studies, it is necessary to clarify which oxygen concentration in AM parts with oxidation-critical materials can be achieved with the present nozzle types with and without a shield gas chamber at different gas settings. In the case of Ti\({}_{6}\)Al\({}_{4}\)V, the microstructure must not contain an oxygen concentration greater than 2000 ppm. Furthermore, an oxidation model should be developed that can be used to estimate whether the process is oxidation-critical or not. Conceptualization, D.K. and K.W. ; methodology, D.K. and A.M.; software, D.K. and A.M.; validation, D.K., A.M., T.S. and K.W. ; investigation, D.K. and A.M.; resources, K.W. ; writing--original draft preparation, D.K. ; writing--review and editing, A.M., T.S. and K.W. ; visualization, D.K. ; supervision, T.S. and K.W. ; project administration, D.K. and K.W. ; funding acquisition, K.W. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The datasets generated during and/or analyzed during the current study are available from the corresponding authors on reasonable request. The authors declare no conflict of interest. Relative coordinates in mm of the oxygen point grid measurements of the three-jet nozzle. The center of the coordinate system (\(x=0,y=0,z=0\)) is in the hole of the hole plate. \begin{tabular}{c c c} \hline \hline \(x\) & \(y\) & \(z\) \\ \hline  
\hline \hline \end{tabular}   
**Table A1. ** Relative coordinates in mm of the oxygen point grid measurements of the three-jet nozzle. The center of the coordinate system (\(x=0,y=0,z=0\)) is in the hole of the hole plate.