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winterev 05

The second of the WINTEREV meetings was held at UPC, Barcelona on 24-25 February 2005 hosted by Professor Luis Llanes of the Department of Materials Science and Engineering, Universitat Politècnica de Catalunya. The WINTEREV was attended by 17 persons from twelve organisations from across industry, academia and RTOs. Because hardmetals are made from micrometre-sized particles the measurement of "fine" particle sizes is an issue of substantial interest. Particle size and distribution, in particular changes in the form of the distribution and particle shapes are very important. The suitability of fine powders depends not only on average size but also on size distribution and chemistry since coarse particles can be a source of weakness in the final product and very small particles (fines) can induce problems in sintering through their high surface area and consequent reactivity. The number of potential methods is large and it is not easy to decide which is the most appropriate technique for solving a given size measurement problem. Often, there are few good technical reasons to expect similar results from different methods. However, the repeatability and reproducibility of each technique is very important. Submicron carbide nomenclature is complicated by the lack of an agreed method for powder size measurement. The traditional Fisher sub-sieve sizer reaches its limit at about half a micrometre, so other methods based on laser diffraction, gas adsorption, and Brownian motion have been used. Nanostructured materials are also on the horizon. It is important for industry to have methods suitable for quantifying powders and grain structures and to have knowledge of their accuracy and validity.

The complex process route from raw material to final sintered product highlights the need for measurement techniques. The ultimate driver is structural control in the final sintered materials, for which grain size measurement techniques are required and a new ISO standard "WC Grain Size in Sintered Materials" has been developed. This includes seven categories of size from Nano (<0.2 mm) up to Extra Coarse (>6 mm) as measured by the intercept value technique. EBSD is another new technique at the development/research stage for hardmetals but it may be tedious for sub micron grains with current technology. It is important to know the uncertainty inherent in the measurement method.

WINTEREV 05 Presentations

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