Some Observations on the Milling Behaviour of Nitrogen-Atomized Cobalt Powder

Abstract

Cobalt powder was dry-milled using a high-energy vibrational ball mill. Examination of the particle appearance using a scanning electron microscope established that the original spherical particles were initially reduced to platelets and that fracture of these platelets resulted in a marked decrease in the average particle size as milling continued. During milling, pressure welding of fine particles onto the surface of the platelets resulted in an increasingly roughened surface appearance with increasing time. After 32 h, the powder consisted essentially of porous agglomerates of fine, almost equiaxed particles.