Influence of milling media on the structure and agglomeration behaviour of some hardmetal powder

This paper presents the influence of milling media on the structure and morphology of WC-Co powders for sintered tools. WC-Co powders have been milled in two different organic media, acetone and isohexane. The characterisation of the as-milled samples has been done by X-ray diffraction, scanning electron microscopy (SEM) and differential scanning calorimetry. The mean crystallite size decreases with milling time for the samples processed in acetone, while in the case of isohexane, the crystallite size stays at a relatively constant value when increasing the milling duration. The calculated mean crystallite size is below 50 nm for any milling duration, with larger values for acetone (16-46 nm) as compared to isohexane samples (10-12 nm). The SEM revealed that the dried powder is composed of agglomerated submicronic particles, and at high magnification, the presence of nanoparticles is noticed. The density of the aggregates was linked to the polarity of the solvents, which influences the sedimentation kinetics.