LOW OXYGEN CONTENT FINE SPHERICAL PARTICLES AND PROCESS FOR PRODUCING SAME BY FLUID ENERGY MILLING AND HIGH TEMPERATURE PROCESSING

摘要

ABSTRACTA powder material and a process for producing the materialare disclosed The powder material consists essentially ofspherical particles selected from the group consisting ofmetals, metal alloys, ceramic glasses, crystalline ceramicmaterials, and combinations thereof The material isessentially free of elliptical shaped material and elongatedparticles having rounded ends The material has a particle sizeof less than about 20 micrometers in diameter and has an oxygencontent of less than about 0.8% by weight. The process formaking the spherical particles involves reducing the size of astarting material to produce a finer powder essentially all ofwhich has a particle size of less than about 20 micrometers indiameter. This is done by fluid energy milling. The finer powderis entrained in a carrier gas and passed through a hightemperature zone at a temperature above the melting point of thepowder, the temperature being from about 5500°C to about17,000°C and created by a plasma jet, to melt at least about 50%by weight of the powder and form spherical particles of themelted portion. The powder is then rapidly and directlysolidified while in flight. The carbon content of the particlesis no greater than that of the starting material.16