The Influence of Gas Cooling in Context of Wire Arc Additive Manufacturing-A Novel Strategy of Affecting Grain Structure and Size

The continuous building process in additive manufacturing with gas metal arc welding (GMAW) provides the main advantage of a decreased processing time but leads to a high heat input in the built work piece. Especially geometrically small parts are affected by a coarse and constantly growing grain structure throughout the continuous reheating process. A novel approach of influencing the temperature-time regime during the additive manufacturing process is an application of additional cooling gas. Experimental trials with argon, hydrogen and nitrogen were carried out and analyzed by means of thermal imaging, hardness measurement and microscopy. The experimental results showed a significant influence of cooling gases on the temperature during the building process. Hence, grain structure and size can be modeled to a homogeneous microstructure by the composition of the gas.