SUB-MICRON DEFECTS IN RAPIDLY SOLIDIFIED TYPE-304 STAINLESS-STEEL POWDERS CONTAINING NOBLE-GASES

The purpose of this work is examine the defect microstructure of 304 SS powders processed by different atomization methods. The powders examined were processed by centrifugal atomization (CA) and vacuum gas atomization (VGA). In the CA process the molten droplets exiting from the spinning cup were convectively cooled with flowing helium. The VGA process involves pressurizing and mechanical mixing of the melt with argon. The entrapped argon in the melt as well as the carrier argon associated with the melt stream produces the molten droplets. Optical microscopy was performed on screened particle sizes to resolve the morphological features such as porosity and solidification microstructure.