PRODUCTION AND CHARACTERIZATION OF METAL POWDERS BY ATOMIZATION FOR ADDITIVE MANUFACTURING

Abstract

The characteristics of the powder used in powder-bed-based additive manufacturing play a significant role in determining both the process conditions and the quality of the parts manufactured. Therefore, it is essential to assess powder characteristics, particularly particle morphology, size distribution (PSD) and rheology. This study aims to characterize the size distribution and morphology of metal powders commonly used in additive manufacturing, such as AlSi10Mg, Inconel-718, Ti6Al4V, titanium, stainless steel and ultrasonic atomized powder AlSi12. The study applies various PSD models to fit the measured volume- and number-based size distributions and conducts a statistical analysis to identify the best-fitting models. Additionally, the study utilizes shape analysis of SEM images based on elliptic Fourier series to quantitatively characterize particle morphology. The study reveals that AlSi10Mg powder exhibits the widest size distribution, while Inconel-718 and stainless steel powders have the narrowest distributions. The ultrasonic atomized AlSi12 powder produced at an angle of 2.5° has the widest particle size dispersion in terms of volume while AlSi12 powder produced at an angle 5° number, according to the data. The narrowest volume- and number-based particle size distributions, however, are shown by AlSi12 powder produced at angle -2.5°and AlSi12 powder produced at angle 0°, respectively. Metal particles, except for AlSi10Mg, are almost spherical, with elongation ratios ranging from 0.90 to 1. AlSI12 exhibit the highest level of sphericity, while AlSi10Mg particles have a rougher surface structure. The Nukiyama-Tanasawa and log-normal distributions fit the experimental PSDs better than the normal and Rosin-Rammler models. Powder rheology tests using FT4 rheometer indicate that AlSi10Mg has the lowest BEF value, resulting in good flowability, Inconel-718 powder forms a denser bed, and titanium has the highest cohesion value and the lowest flow function value, making it the most flowable among all the powders tested. Additionally, we examined the correlations between the powder's rheological properties, measured by a Hall flowmeter, tapped density tester, and FT4 powder rheometer, and the PSD and shape indices using Spearman's coefficient test. The results of this study can assist in selecting the appropriate metal powder for specific additive manufacturing applications.