Low oxygen content iron group based and chromium based fine spherical particles and process for producing same by fluid energy milling and temperature processing

摘要

A powder material and a process for producing the material are disclosed. The powder material consists essentially of iron group based and chromium based spherical particles. The material is essentially free of elliptical shaped material and elongated particles having rounded ends. The material has a particle size of less than about 20 micrometers in diameter and has an oxygen content of less than about 0.8% by weight. The process for making the spherical particles involves reducing the size of a starting material to produce a finer powder essentially all of which has a particle size of less than about 20 micrometers in diameter. This is done by fluid energy milling. The finer powder is entrained in a carrier gas and passed through a high temperature zone at a temperature above the melting point of the powder, the temperature being from about 5500 DEG C. to about 17,000 DEG C. and created by a plasma jet, to melt at least about 50% by weight of the powder and form the spherical particles of the melted portion. The powder is then rapidly and directly solidified while in flight. The carbon content of the spherical particles is no greater than the carbon content of the starting material.