# Wire Arc Additive Manufacturing of Stainless Steels: A Review
## 1 Introduction
\begin{table}
\begin{tabular}{l l l} \hline \hline
**Abbreviations** & \multicolumn{1}{c}{**Phrases**} \\ \hline
3D & Three-dimensional \\ AD & As-deposited \\ AD+H900 & As-deposited plus H900 ageing treatment \\ AM & Additive manufacturing \\ BJ & Binder jetting \\ CGEF & Complete grown equiaxed ferrite \\ CMT & Cold metal transfer welding \\ DED & Directed energy deposition \\ DED-GMA & Directed energy deposition with gas metal arc \\ DED-L & Directed energy deposition-laser \\ DSS & Duplex stainless steel \\ DWF-PAM & Double-wire feed and plasma additive manufacturing \\ EL & Elongations \\ GMAW & Gas metal arc welding \\ GMAW–CMT & Gas metal arc welding with the cold metal transfer process \\ GTAW & Gas tungsten arc welding \\ H & Horizontal \\ IGEF & Incomplete grown equiaxed ferrite \\ LMPD & Laser metal powder deposition \\ ME & Material extrusion \\ MJ & Material jetting \\ PAW & Plasma arc welding \\ PBF & Powder bed fusion \\ PBF-L & Powder bed fusion-laser \\ RP & Rapid prototyping \\ SG & Shielding gas \\ SG1 & Shielding gas1 \\ SG2 & Shielding gas 2 \\ SL & Sheet lamination \\ SLM & Selective laser melting \\ ST & As-deposited followed by solution treatment only \\ ST+H900 & As-deposited followed by solution treatment and H900 ageing \\ SWF-PAM & Single-wire feed and plasma additive manufacturing \\ UTS & Ultimate tensile strength \\ V & Vertical \\ VP & Vat photo-polymerization \\ WAAM & wire arc additive manufacturing \\ YS & Yield strength \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Commercial WAAM machines. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Company** & **Model** & **Details** & **Country** \\ \hline \multirow{2}{*}{Gefertec GmbH} & GTarc3000-3 & \multirow{2}{*}{A three-axis system for the production of parts} & \multirow{2}{*}{Germany} \\  & WAAM machine & up to 3 m\({}^{3}\) with a maximum mass of 3000 kg. & \\ \hline \multirow{2}{*}{Mazak} & \multirow{2}{*}{VARIAXIS j-600 AM} & \multirow{2}{*}{Applied to the production and repair of aerospace parts, molds, and dies and oil-drilling components.} & \multirow{2}{*}{Japan} \\  & & & \\ \hline \multirow{2}{*}{Addilan} & \multirow{2}{*}{Addilan VO.1} & A closed loop control system and an inert chamber with a special loading and unloading system. & \multirow{2}{*}{Spain} \\  & & & system. \\ \hline \multirow{2}{*}{Nanjing Enigma Automation} & \multirow{2}{*}{ArcMan-600} & Building Dimensions: 400 \(\times\) 400 \(\times\) 600 mm & \\  & CO., Ltd. & \multirow{2}{*}{China} \\ \cline{1-1} \cline{5-5}  & & Layer thickness resolution: 0.5–0.25 mm & \\ \hline \multirow{2}{*}{Nanjing Zhongke Raycham} & \multirow{2}{*}{RC-WAAM-3000} & Building Dimensions: 3000 \(\times\) 2000 \(\times\) 1000 mm & \\  & & Max wire feed rate: 1–5 m/min & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of abbreviations. The WAAM process can be achieved through gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), plasma arc welding (PAW), or cold metal transfer welding (CMT) for melting metal wires and constructing a 3D component layer by layer [50; 51; 52; 53; 54]. Among these, GMAW is limited by the minimum wall thickness and coarse sidewall surface owing to its relatively large melt pool and heat input [50; 55; 56]. To surpass the limitations, cold metal transfer welding (CMT) [57; 58; 59] can be adopted to achieve a very smooth droplet detachment by minimizing the arc burn time and moving the wire electrode back and forth at frequencies up to 150 Hz [60; 61]. TIG-WAAM has very clean deposition and can manufacture metal components with high quality [62; 63]. In theory, metals with good weldability could be potentially used for WAAM process and so far researchers have successfully fabricated 3D objects in Ti-based [64; 65; 66; 67], Al-based [68; 69], steel-based [70; 71], and Ni-based [72] alloys. Stainless steels--such as austenitic, martensitic, and duplex stainless steels--are good candidates for WAAM due to their excellent mechanical properties and high corrosion resistance [73].