# Development of an Alternative Alloying Concept for Additive Manufacturing Using PVD Coating
## 3 Results  
### Influence on the Arc  
Figure 5 shows the individual arc recordings of the modified filler metals. The mean arc lengths over the process are shown as an example. The mean arc lengths were averaged over 50,000 frames per second. The modified filler metals with the elements Al, Cr, Nb, Ni and titanium to be investigated are shown. In addition, the base wire is examined. Usually, this is supplied with a copper layer, which represents the base wire + Cu. However, for the investigation of the modifications, a bare white wire without a copper layer is used. For this reason, these two types of base wire are also examined. Figure 4: PVD coating on wire surface [16]. Figure 3: PVD coating process [27; 28]. The first theory explaining the change in arc length is that it actually remains constant and only the exposed part of the arc appears longer or shorter. This means that with a shorter arc, a large part of the arc is covered, and the arc base is moved deeper into the component. This would result in an increase in the burn-in. To test this thesis, the individual beads are separated, and the seam geometry is closely examined. The comparison of the different seam geometries shows that the seam volume, the width and the penetration change. If the penetration is set in relation to the arc length, a correlation between exposed arc length and penetration can be recognised. However, this is not a question of a constant arc length that shifts. It can only be said that the depth of the penetration decreases with increasing arc length. Furthermore, current and voltage were recorded during the welding tests to be able to recognise an influence on the applied power and a possible change in the values due to the coatings. For the evaluation, interpolation times of 1 s and 10 s were selected for each recording. The welding current source is a source with constant voltage characteristics. This means that the present source regulates the current and tries to keep the voltage relatively constant. According to [PERSON] [29], the arc length is also dependent on the current. The shorter the arc, the higher the current and the lower the voltage. The same applies analogously for a longer arc. This relationship becomes apparent when an extension of the arc is considered, and it results in a greater distance being passed. The voltage increases accordingly. If the distance is shorter, a lower voltage is necessary, and a higher current can be transported. However,  
Figure 5: Arc recordings. the recorded values show that the current increases with aluminium and especially with titanium. However, the greatest arc lengths can be seen with these two coatings. These values are in clear contrast to the theory that with a longer arc length, the voltage increases and the current decreases. In addition, increasing the current usually causes a larger burn-in. This is not the case here because the penetration decreases for both aluminium and titanium. However, this theory refers to a constant burning arc, where all parameters remain the same except for the distance of the torch to the workpiece, which changes the arc length and counter-regulates the current source. Under these constant conditions, the behaviour of current and voltage in relation to the arc is exactly as described. In this work, however, the nature of the welding wire is changed, which has further effects on the arc and its properties. Due to the thin film coating of additional elements on the wire surface, there must be effects on the arc that change its length. Another theory is the energy required to bring an element into the gas phase. For this purpose, the sublimation energy is used and related to the layer thickness and its element-dependent molar mass. The necessary sublimation energy to be applied, here related to 1 mm\({}^{3}\) wire, shows that different energies can result. However, no analogy can be drawn between the necessary energies and the resulting arc length. Furthermore, an influence of the electrical conductivity of the coated elements was considered.