Characterization of 316 L stainless steel powders produced by supersonic gas atomization

316 L stainless steel powders were prepared by supersonic gas atomization.The characteristic of the powder particles was investigated by means of laser particle size analyzer,scanning electron microscopy(SEM),optical microscopy(OM) and X-ray diffraction(XRD) technique.The result indicates that the mass median particle diameter is about 24 μm and the geometric standard deviation δ is 1.75.Three main types of solidification microstructures were observed in the powders:well-developed dendrite,cellular and a mixture of dendrite and cellular.XRD measurements show that γ-austenite phase is found in the big particle while small particle is a composite consisting of δ-ferrite and γ-austenite phases.The cooling rate is inversely related to the particle size,i.e.,it increases with decreasing particle size.The mean cooling rates of melt droplets range from 10⁴ to 10⁷ K·s^-1.