Effect of Atomization Parameters on Size and Morphology of Al-17Si Alloy Powder Produced by Free Fall Atomizer

In the present work the effect of process parameters on the characteristics of Al-17Si alloy powder produced by gas atomization using a free fall nozzle of different apex angles. The axial gas velocity away from the nozzle exit is measured for different operating pressures. The alloy was melted to a superheat temperature of 100,150 and 200° C and atomized by varying the gas flow rate and melt flow rate. The powder produced during gas atomization process generally exhibits a wide size distribution. ASTM standard sieve with vibratory shaker is used for powder analysis. The characterization of powder particles was accomplished by the parameters such as mass median, average size of powder particles; standard deviation and morphology of powder were studied by scanning electron microscopy. It is observed that decrease of apex angle results in axial velocity decreases in entire applied gas pressures range. Increase in apex angle results in decrease of gas jet length to metal stream collision, the median particle diameter of the powder increases resulting in decrease in particle irregularity. The median particle diameter of the powder has been shown to decrease almost linearly with increase in gas to melt flow (G/M) ratio. The sauter mean diameter variation, however, decreases slowly with increase in G/M ratio. Median particle diameter is significantly reduced with increase in the melt superheat.