ON THE CONTROL OF POWDER-SIZE DISTRIBUTION IN FULL-SCALE GAS ATOMIZATION OF NICKEL-BASED ALLOYS

The relationships between the main process parameters in gas atomizati on and powder-size distribution were studied in this work. The aim was to improve the understanding of the process as a basis for subsequent work on process optimization. 2 nickel-based alloys were used in the study and the experiments were performed using design of experiment pr inciples in an industrial setting. The method of design of experiment has proven to be a powerful tool to deepen the understanding of the pr ocess of gas atomization. Statistically-significant effects on size di stribution for changes of parameter settings could be distinguished in the experiments where gas pressure, alloy composition and angle betwe en melt stream and gas jets (apex angle) were found to be the most imp ortant parameters; an unanticipated interaction between gas pressure a nd alloy composition was also found. In contrast to prior expectations , the diameter of the melt orifice and the superheat (temperature exce eding the liquidus temperature) proved to have a negligible effect on the size distribution of the atomized powder in the parameter range th at was selected for these experiments. The 2 methods used to analyze t he powder-particle size distribution, laser diffraction and sieving, g ave different numerical results. However, changes in the parameter set tings studied gave the same major effects on the powder particle size distribution, independent of method. (C) Munksgaard, 1997.