**2.1 Plasma arc welding (PAW)**

Plasma arc welding process shall be employed for AM using filler material for the fabrication in either powder form or wire form. This may familiarly be called as Plasma Transferred Arc Welding (PTAW), an important variant of PAW. This welding process is found to be the best process for the depositions to suit surfacing or cladding processes with several materials. The same deposition approach may also simply be extended to a very simple approach for AM as like multi-layers surfacing or cladding. This process is capable of separating the energy input and the weld metal flow entirely from the filler metal. This process is applicable to different type of materials.

### **2.2 Gas metal arc welding (GMAW)**

GMAW is a more frequently employed famous welding process for many decades in metal surfacing, cladding, and additive manufacturing too. Thus, this process is very familiar nowadays for WAAM because of its suitability. In recent years, much focus has been given to the development of control systems for welding arc power and this leads to the development of new process variants such as CMT-GMAW [7]. Furthermore, these controlled short arc welding processes can be ranked high by innovative wire feed control to achieve control on droplets. Also, a variant called the multi-wire process has been developed particularly to improve the mass of the deposited metal.

### **2.3 Gas tungsten arc welding (GTAW)**

This GTAW is familiarly known as Tungsten Insert Gas (TIG) welding. The important major benefit of this TIG welding process is that the separation between the filler metal and heat energy input is highly possible. The possibility for using more than a single wire during the process made TIG an well-suited process for WAAM. A variant of TIG called the pulsed TIG welding process has shown a very good melt pool shape thus to suit for additive manufacturing. Various properties of the AC-TIG and pulsed TIG welding processes are also under rigorous investigation to meet the WAAM process. It is believed that GTAW would be a great choice for WAAM in near future.

### **2.4 Submerged arc welding (SAW)**

SAW can be a successful welding process for AM but positioning the flux plays an important role in this process because of this reason the flexibility of this process *Welding Based Additive Manufacturing: Fundamentals DOI: http://dx.doi.org/10.5772/intechopen.104768*

**Figure 3.** *Skeleton arc WAAM.*

is limited AM. For carrying the electrode and current, a welding gun and cable set are used and thus deliver the flux to the arc. The flux to be supplied depends upon the position of the gun. On the other hand, the torch is attached to the motor that is feeding wire and takes necessary actions regarding current to take tips for the reason of transmitting the welding current to filler wire. SAW would become complex by including additional devices like weavers, seam followers, and work rovers, etc. Because of these complex reasons SAW has not been identified with ease for the WAAM process.
