Chapter 22 - Production of Cobalt and Cobalt-Alloy Powders

Abstract

The hydrometallurgical technique, the reduction of oxides, atomization, carbonyl processing, the electrolytic method, the amalgam technique, the ultrasonic spray pyrolysis of cobalt, and cobalt-alloy powder production are discussed in this chapter. The fundamentals of the leaching autoclave process based on the ammoniacal pressure leaching of the sulfides to produce soluble nickel and cobalt hexamine sulfate complexes are considered. Properties of composite powders based on autoclave cobalt coating of different metal seed types are presented. The carbide-containing alloys and alloys containing the Laves phase—the two types of commercially effective cobalt-base hardfacing alloys—are described. The plasma-transferred arc hardfacing process is considered. The composition of several typical hardfacing alloys is presented. Spherical cobalt powders made by ultrasonic spray pyrolysis of cobalt nitrate aqueous solutions followed by thermal decomposition of generated aerosols in a hydrogen atmosphere are discussed. The characteristic structure and surface morphology of cobalt and cobalt-alloy powders are displayed by SEM and TEM micrographs. The high toxicity of work materials in the carbonyl and amalgam processes is revealed. Safety aspects of powder and granule production are considered.