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((NH_4)_6(H_2W_12O_40)cdo4H_2O,AMT) and cobalt nitrate hexahydrate (Co(NO_3)_2.6H_2O). spray dried W-Co salt powders were calcined for 1 hr at 700°C 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 H_2. The WO_3/CoWO_4 composite oxide powders were obtained by calcinations at 700°C. 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 800°C by TEM was smaller than 50 nm.

• Keywords: Mechanochemical process;Nanostructure;WC/Co;