Abstract
A new approach to produce nanostructured WC/Co composite powders by a mechanochemical process was made to improve the mechanical properties of advanced hardmetals. Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution from ammonium metatungstate(<TEX>$(NH_4)_6(H_2W_{12}O_{40})\cdo4H_2O$</TEX>,AMT) and cobalt nitrate hexahydrate (Co(NO<TEX>$_3$</TEX>)<TEX>$_2$</TEX>.6<TEX>$H_2O$</TEX>). spray dried W-Co salt powders were calcined for 1 hr at <TEX>$700^{\circ}C$</TEX> in atmosphere of air. The oxide powder was mixed with carbon black by ball milling and this mixture was heated with various temperatures and times in <TEX>$H_2$</TEX>. The <TEX>$WO_3/CoWO_4$</TEX> composite oxide powders were obtained by calcinations at <TEX>$700^{\circ}C$</TEX>. The primary particle size of W/Co composite oxide powders by SEM was 100 nm. The reduction/carburization time decreased with increasing temperatures and carbon additions. The average size of WC particle carburized at <TEX>$800^{\circ}C$</TEX> by TEM was smaller than 50 nm.
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