*3.2.2 Gas tungsten-wire arc additive manufacturing*

Gas Tungsten-Wire Arc Additive Manufacturing (GT-WAAM) is the same as WAAM process with one difference; a localized gas tungsten shielding is used in GT-WAAM. The tungsten reduces the oxidation on the surface and increases the quality of the layer [15]. There are methods of Direct Energy Deposition (DED) available, and they function on the same concept of WAAM and GT-WAAM (welding method) and they are as follows:

**245**

*An Investigation of the Metal Additive Manufacturing Issues and Perspective for Solutions…*

Several metals (alloys) can be utilized in the MAM method. In this section, the

2.**Titanium alloys:** Ti6Al47 is the dominant titanium alloy; it can be used for the MAM method. This alloy is mainly implemented with SLM, EBM powder-bed and other MAM processes. However, printing parts with these alloys exhibits residual stress and fatigue as defects which affects the quality of the parts. Ti64 is also assigned as a common titanium alloy for MAM. It has high corrosion resistance and is implemented with DMLS-MAM process. The part produced by this process can be used for medical application, aerospace, firearm, and

automotive parts which require high corrosion resistance [9, 15]**.**

3.**Iron-based alloys:** Different types of iron alloys can be utilized in MAM method: 316 L stainless steel, 314 L stainless steel, 15–5 stainless steel, 17–4 stainless steel, and Fe-6.9% Si, maraging steel MS1 and more. These iron-based alloys can be used in powder-bed fusion methods, such as SLM and DMLS. The MAM parts produced from stainless steel can be used for high corrosion resistance and strength applications such as medical, firearms, energy and automa-

4.**Super nickel/chromium alloys:** Nickel/Chromium alloys include IN718, IN625, HX, MK500, and Haynes 282. The parts produced from the powder of these alloys have excellent heat and corrosion resistance with hardness of 40–47 HRC. Different sized parts can be produced from these alloys with different applications such as rockets, space, aerospace, firearm, energy, and automotive. DMLS

5.**Other alloys:** The above-mentioned alloys are the most famous alloys which are used to produce parts by MAM method. However, there are other types of metals that can be utilized to produce parts by different processes of MAM method. Some of these metals can be a real challenge to be melted layer by layer from their powder. For example, Inconel 718 is utilized by EBM process, Inconel 625 is produced by SLM process, copper is printed by EBM process, and Fe65Cu17.5Ni17.5 is printed by SLM. Most of these metals (alloys) can be used to produce parts for different applications, however some of them are still in the stage of study [29].

MAM method has no limitation on size, shape and geometric complexity. Small, medium and large sized parts with complex geometry can be obtained from MAM method. For example, different size and geometry of gears, pistons, pullies, junctions,

and SLM MAM methods can also be used with these alloys [11, 30].

1.**Aluminum alloys:** Al-Si, Al-Si-Mg, and AlSi10 are the most commonly used aluminum alloys for the MAM method. These materials can be used for powder-bed fusion especially in DMLS and SLM process. Performance of these alloys can be enhanced by adding Zr and Sc. Wire based additive manufacturing also uses the aluminum alloys. Aluminum powder is good for parts with thermal properties and low weight, and it is a relatively better choice for parts with thin wall and complex geometry. According to current studies, the alumi-

*DOI: http://dx.doi.org/10.5772/intechopen.93630*

**4. Metal additive manufacturing materials (alloys)**

num alloys will be the major metal in MAM [29].

tion, and tooling applications [30, 31].

**5. Parts size produced by MAM**

most important metals (alloys) are listed as follows:


*An Investigation of the Metal Additive Manufacturing Issues and Perspective for Solutions… DOI: http://dx.doi.org/10.5772/intechopen.93630*
