## 1 Introduction  
Additive manufacturing (AM), also known as 3D printing, is a new type of manufacturing that creates three-dimensional parts layer by layer by converting data from computer-aided design (CAD) data to a final part [1, 2]. Despite subtractive manufacturing techniques, which are based on shaping or cutting, AM adds material to build the final part. This technique allows industries to have more flexibility in fabricating complex parts while reducing production time and waste material. In 2010, the American Society for Testing and Materials (ASTM) group \"ASTM F42--Additive Manufacturing\" [3] classified AM into seven groups, namely material jetting [4], binder jetting [5], material extrusion [6], VAT photopolymerization [7], powder bed fusion [8], sheet lamination [9], and directed energy deposition [10, 11]. In these methods, the feeding material is either powder or wire (metal or polymer), depending on the process requirement. Recently, wire-based DED (WDED) has been accentuated by research centers and industries, particularly material engineering units. Figure 1 indicates a flow chart of fabrication via the AM process. Figure 2a-d depict the number of studies, fields of research, bibliographic map, and contributing countries in the field of WDED, respectively. Figure 2a shows the number of research studies over a period of two decades. This growth has been particularly sharp in recent years, which reflects the rapid advancements of WDED technology across various industries. As can be seen in Figure 2b, DED has been mostly used in the engineering field, given the demand for high-performance, complex components that can be tailored to specific requirements in industries such as aerospace, automotive, and manufacturing. Figure 2c,d show the field map, which highlights the geographical distribution of DED  
Figure 2: Number of publications in the field of WDED, based on Scopus database and Web of Science. (**a**) Number of publications per year. (**b**) Research fields in WDED. (**c**) Bibliographic (filled) map in WDED. (**d**) Contributing countries. WDED is categorized based on feeding materials and energy sources, shown in Figure 3. In laser metal deposition (LMD), a laser beam melts the material (powder or wire) to create a melt pool on the metallic substrate, as shown in Figure 3a. Electron beam DED is similar to LMD, but the main difference is the energy source for melting the material, which can be powder or wire, as shown in Figure 3b. Wire and arc additive manufacturing (WAAM), as shown in Figure 3c, is a combination of two manufacturing processes, namely AM and gas metal arc welding (GMAW). In this method, the process is carried out by a welding robot, which has an attached welding torch integrated with a power source. Molten DED, Figure 3e, is a method that mainly focuses thermal energy to melt and deposit material (mostly wire, and in some cases, powder) onto the substrate. Friction DED, Figure 3e, is a solid-state AM process that does not melt material but mostly relies on the frictional heat generated between the deposition tool and substrate. Figure 3: \(Cont\). Table 1 provides information and classifies the DED techniques. Figure 3: Classification of WDED. (**a**) Laser metal deposition [12], (**b**) electron beam DED [13], (**c**) wire and arc additive manufacturing (WAAM) [14], (**d**) molten DED, (**e**) friction DED [15].