Microstructure development during sintering and heat-treatment of cemented carbides and cermets

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.

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

Cemented carbide powders milled for various times have been studied with respect to the shape and internal structure of the grains. The shrinkage of powder compacts during heat-treatment was recorded dilatometrically. The major effects of milling seem to be to alter the grain size and morphology of the powder and to form a fine dispersion of small particles of Co3O4.

T. Johannesson

Papers

Some aspects of the milling of cemented carbide powder