This project aims at understanding the effect of the process gas on the interaction of the laser beam with the powder bed during the Laser-Powder Bed Fusion process. Today, the process gas is considered a minor parameter compared to for example the laser power or the scanning speed. Its role has been limited to ensuring a laminar flow over the building area and removing projections.
To fulfill this, the inert argon and sometimes nitrogen are the two options widely available today. However, the scope of available industrial gases and gas mixtures is broad, and has been extensively developed thanks to progress in areas like welding. Gas recipes have been defined for very specific applications such as increased weld penetration.
In this project, the possibility to control the melt pool stability by acting on the heat input and the related generation of by-products is studied. In that respect, new gases are investigated to understand the influence of the process gas density and thermal properties. Among these, helium and argon-helium mixtures are employed. In addition, the effect of the atmosphere purity is analyzed as it can be expected to be critical for alloys like Ti-6Al-4V exhibiting a high affinity for oxygen and nitrogen. The result of this work have been summarized in a scientific paper published open-access[1].
The figure depicts the productivity gain that can be obtained when using a tailored process gas and laser parameters allowing to obtain similar density and mechanical properties as when using argon and standard process parameters.
The study continues and focuses on the use of in-situ monitoring tools to better understand the effect of the gas on the melt pool stability and quantify the generation of process by-products.
Researchers: Camille Pauzon and Eduard Hryha, Chalmers
Industry partner: Linde Gas, AGA Gas
Material: Ti-6Al-4V
Additive process used: Laser-Powder Bed Fusion (EOS M290)
Process gas: Argon, helium, argon-helium mixtures, oxygen monitored