Speaker
Description
In additive manufacturing of metals, high quality powder with uniform size distribution and spherical, satellite-free particles of defined size is required. SMS group has built-up a metal powder production plant which operates using the close-coupled atomization principle. For reliable plant operation, it is important to understand the atomization mechanisms, i.e. the effect of plant parameters such as nozzle geometry or melt and gas flow rates on the particle size. Thus, the challenge lies in modeling the atomization process under extreme plant conditions.
A cooperative project with five partners from India and Germany is being funded by the Indo-German Science & Technology Center with support from the Federal Ministry of Education and Research. The project builds on a coupled approach of laboratory experiments, numerical simulations and plant operation to develop models and design guidelines for production plants.
The basis is the production plant, which produces austenitic, nickel based, and in the future maraging steel powder. The nozzle system has been replicated in a one-to-one scale laboratory test rig. Here, the plant conditions are reproduced using heated water and air as fluids, satisfying most dimensionless numbers of the production plant. The test rig allows investigation of the interaction between shock/expansion waves and water flow by focusing Schlieren optics, high-speed imaging and phase Doppler anemometry. On the Indian side, a shock-droplet-interaction test rig and a supersonic wind tunnel have been built-up. Using high-speed shadowgraphy and Schlieren optics, the mechanisms of droplet breakup are visualized.
Parallel to the experimental work, CFD models are being developed to predict the behavior of the ligaments beneath the nozzles, liquid-gas-interaction and droplet solidification. Promising results have been computed for the flow of water and air, matching the conditions of the laboratory test rig.