Metal Additive Manufacturing Conference - MAMC 2022

Thermophysical property data such as surface tension, density and viscosity of liquid metals and alloys are key input-parameters for various simulations in fundamental as well as in industry related research. The field of additive manufacturing (AM) became a technological trendsetter in the last years and consequently, the interest in thermophysical property data gained more and more momentum as researchers and developers build and run simulations to better understand and optimize the processes involved in various AM techniques. In case of surface tension and viscosity, however, ab-initio models to calculate said properties for steels and alloys hardly exist and simulations have to rely on experimental data instead. Moreover, surface tension for instance is influenced by surface-active elements like sulfur or oxygen, which is why precise experimental data of the material actually used is to favor.

But measuring thermophysical properties of liquid steels and alloys is a challenging task due to the high temperature and high chemical reactivity of the melt. Hence, a measurement method that allows a contact- and container-less processing of the melt is favorable. The oscillating drop (OD) method in combination with an electromagnetic levitation (EML) device allows to elegantly satisfy these requirements. The sample is levitated freely in an inert gas atmosphere and surface tension and density are obtained from the analysis of high-speed videos while the sample’s temperature is measured simultaneously using pyrometry.

In this talk, we will present results from such EML experiments that were performed at the Institute of Experimental Physics (IEP) at Graz University of Technology (TU Graz), among them measurements on products by voestalpine BÖHLER Edelstahl GmBH & Co KG (for instance on BÖHLER W360, L625). These data are used at BÖHLER in simulations targeting to better understand and improve the behavior of those materials in powder production (gas atomization) for AM applications. Furthermore, we will give an outlook on thermophysical property measurement activities planned in the future at BÖHLER that will include not only EML but also measurements with a high temperature rheometer (FRS 1800, Anton Paar GmbH) that was recently acquired.