Microstructural Characterization of Rapidly Solidified Type 304 Stainless Steel

ABSTRACTThe microstructures of rapidly solidified Type 304 stainless steel powders produced by vacuum gas (VGA) and centrifugal atomization (CA) have been examined. The solidification morphology and phase distribution have been characterized using optical and scanning electron microscopy, and the relative amounts of ferrite and austenite have been quantified using x-ray diffraction. Most CA powder particles contain both fcc and bcc phases, with the bcc phase predominating at small particle sizes and the fcc phase at large particle sizes. The VGA powder generally contains less ferrite, with very little dependence on the particle size. The ferrite was metastable and transforms to austenite on annealing at 900°C.