**3.5 Shielding gas**

The purpose of using the shielding gas in welding based WAAM is to protect the molten metal during welding against surrounding atmospheric elements. An acceptable flow rate of shield gas is essential to cover the hot weld deposit in WAAM to separate the atmospheric gases and to prevent the action of detrimental oxide, nitride, and porosity formation and porosity. This shield zone could be taken to the side walls also during the fabrication of WAAM components. A very high flow rate could lead to reduced weld penetration. Most commonly used shielding gases are argon, carbon dioxide, helium, nitrogen, hydrogen, and mixers of these gases.
