# Development of an Alternative Alloying Concept for Additive Manufacturing Using PVD Coating
## 1 Introduction  
The continuously growing interest in resource efficiency and the associated development of additive manufacturing processes continue to result in the need to develop adapted filler materials, especially for wire arc additive manufacturing (WAAM) [1]. The functional principle of additive manufacturing is a layer-by-layer construction of structures [2]. Additive manufacturing using metallic materials is divided into powder-based and wire-based additive manufacturing [3]. Adapted material development for powder-based materials with little effort is possible by mixing the powders accordingly [4; 5; 6; 7]. Wire-based additive manufacturing by means of an arc, also known as wire arc additive manufacturing, requires a welding filler material in wire form [8; 9; 10]. A corresponding alloy development up to the wire-shaped welding filler material is very costly. However, the necessity of this alloy development lies in the newly gained design freedom of the components and the possibility of being able to locally adapt material properties in a targeted manner depending on the load, for which the corresponding alloys are required [11]. It should also be noted that when components are built up in layers, a low surface tension means that the dimensional stability cannot be maintained. This means that the required geometry and its tolerances cannot be guaranteed, which are relevant parameters [12; 13; 14]. However, to develop new filler metals for this case, it is necessary to prepare steel melts, to alloy them based on secondary metallurgy and to then draw a welding wire for the process [15]. This procedure is costly and time-consuming. For this reason, a new innovative alloy concept is investigated for the development of a new type of filler metal with regard to wire arc additive manufacturing. For this purpose, a thin film coating is applied to a welding filler wire.  
HSLA (high-strength low-alloy) steel is used as a filler metal. These low-alloy filler metals can be alloyed very well by means of PVD thin-film coating due to the low proportion of alloying elements. Such materials are used for complex bionic structures or spare parts with an adapted chemical composition that has to be procured quickly.  
For the development of an alternative alloying concept, it has already been proven by preliminary investigations that a change in the mechanical properties occurs through the application of thin-film coatings on solid wire surfaces. Furthermore, it was shown that an influence on the process properties is caused by the alloying elements present on the surface [16; 17; 18; 19; 20; 21; 22]. In addition, an influence on the process properties and explicitly on the characteristics of the welding arc was recognized. This is due to the ionisation potential of the thin film layer. A validation between the alternative alloy concept and a filler metal produced by secondary metallurgy is described here.  
Within the scope of the investigations, it is to be determined how the influence on the process properties is pronounced and what the reasons are for this. Furthermore, it must be investigated whether the process influence has an effect on the resulting weld seam.  
For qualification of an alternative alloy concept, the influence on the material properties must also be identical to the properties of the classical alloy concept of secondary metallurgy. For this purpose, the effects of the different alloying concepts on the microstructure morphology and the mechanical properties are investigated. If the results agree, the qualification of the alternative alloy concept is successful.