Pierre Foret, Expert Additive Manufacturing, The Linde Group
This presentation will present facts from two studies investigating the influence of shielding gases like Helium and Helium/Argon mixtures on the process parameters, chemical composition and mechanical properties of Ti-6Al-4V and IN718 alloys parts produced by Selective Laser Melting. The results show that tensile strength can be increased while using Helium or Helium/Argon mixtures instead of Argon. In Additive Manufacturing processes based on powder bed fusion, the chamber is commonly inerted with highly pure gases like Argon or Nitrogen. The inert gas role is to remove air from the chamber and avoid any oxidation of the metal during melting. Helium is as Argon and Nitrogen inert to metals. However Helium has a much higher thermal conductivity and a significant lower density. By adjusting the composition of the shielding gas, the distribution of heat to the weld can be modified. These influences parameters like penetration, building speed or energy required. We will show that the role of the atmosphere can be, not only to inert the chamber and remove air, but also to improve the process parameters as well as the mechanical properties.