## 2 Materials and Method
### Specimens Fabrication  
To determine the purpose of the research, two sets of specimens were made according to the ASTM standard E8-E8M-2016a [16]. The geometric shape of the specimens made is of plate-type, having the dimensions represented in the technical drawing from Figure 2.  
The materials used to manufacture the four sets of specimens were equivalent in terms of composition. In the case of the first specimen set, representing parts made by subtractive processes, the specimens were made of laminated sheet, while for the sets of specimens fabricated with hybrid manufacturing technology (DED and CNC milling), the material was X2 CrNiMo17-13-2 as metal powder from Sandvik Osprey(r) powders.  
For the specimens fabricated with subtractive processes, a set of 5 specimens was made and an extra one was made for machine calibration and fixture validation. The specimens were cut from a single stainless steel sheet with 2 mm thickness using a 1800 W laser.  
In the case of the specimens manufactured with hybrid technology, the additive manufacturing process consisted of a DED process using X2 CrNiMo17-13-2 metal powder. The equipment used for the hybrid manufacturing process was a DMG Lasertec 65 DED hybrid machine with a COAX 14-coaxial nozzle technology installed at Compa S.A. Sibiu, Romania. The nozzle assembly is depicted in Figure 3.  
The flow of metal powder is distributed through holes placed at the base of the cone and the laser beam exits through the central hole. The DED additive manufacturing parameters are shown in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Nozzle Type**} & **Nozzle** & **Calculated** & **Adjusted** & **Printing** & **Layer Height** \\  & **Diameter** & **Working** & **Working** & **Distance** & **Federate** & **Layer Height** \\ \hline COAX 14 & 3 mm & 13 mm & 13 mm & 1000 mm/m & 0.9 mm \\ \hline \end{tabular}
\end{table}
Table 2: DED manufacturing parameters.  
Figure 2: Specimen dimensions with respect to ASTM standard.  
Considering that the laser deposition process creates a rough, uneven surface with low geometrical precision [17], to obtain the right dimensions for the specimens, the 3D DED specimen was fabricated with a 2 mm offset on all the part's faces surfaces, which was removed using CNC manufacturing to obtain a precise geometry in conformity with the ASTM standard [16; 18]. Moreover, to study the influence of the height of the DED process on the mechanical properties of the final part, the specimens were fabricated one on top of the other in stacks of 3, as detailed in Figure 4. Considering that we have 3 specimens with an offset of 0.15 mm between them and the base and an addition of 2 mm on top, the total height of the stack is 8.45 mm.  
For the DED process, a nozzle with a diameter of 3 mm and a 13 mm offset between the printed layer and the nozzle were used. As for the powder carrier gas, argon was chosen. The initial laser power was set to 1800 W to aid the bounding of the first layer to the support plate. Progressively, the laser power was decreased by 100 W at each layer until a deposition power of 1400 W was reached. The layer height was 0.9 mm, and the specimens were printed on an S235 JR metal plate with a thickness of 18 mm. To obtain the required geometrical and dimensional precision, the stack of specimens was milled on the upper surface and on the contour. The fabrication process is detailed in Figure 5.  
Figure 4: Stack of 3 specimens prepared for DED hybrid manufacturing.  
Figure 3: COAX 14 nozzle used in the metal powders deposition.  
After the hybrid manufacturing process, the specimens (Figure 6) were removed from the metal plate using an electrical discharge machining process which also sliced the specimen stack to single specimens with a 2 mm thickness. The electrical discharge process used a 0.15 mm wire to separate the specimens.