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 Xray 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.
Materials consisting of a hard phase, usually WC, and a tough binder, traditionally Co, form the most successful class of composite materials, also known as Hard Metals (HM) or Cemented Carbides. Powder metallurgy routes are employed generally for the production of such [1]. The typical processing route of such materials involves mixing the components, kneading and consolidation. Alcohols, alkanes and alkenes are commonly used to limit any excessive heating and oxidation of powders during mixing the components. In this study, we report the results of milling in a more environmentally friendly aqueous milling media. The obtained results are presented comparatively with milling under a traditional media, such as isohexane and acetone. The characterization of the milled samples has been done from the structural, compositional and morphological point of view. Considering our previous results, an important aspect of the milled powder is the carbon content, which dictates the sintering behavior of such parts. The carbon balance investigation performed on a carbon analyzer has revealed no significant differences upon changing the milling media. This work emphasizes the influence of the milling media on the HM powder. HM powders with similar properties have been obtained both by traditional and aqueous milling. The comparative study has revealed that the substitution of the traditional milling media does not influence the carbon content in the HM powder.
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