The sinterability of ultrafine WC powders obtained by a CVD method

Abstract

The sintering behaviour of ultrafine WC powders produced by a CVD method (particle size <0.3μm) and commercial WC powders (particle size ~ 1μm) is investigated in hydrogen and in vacuum. It has been found that ultrafine WC powders have an extremely high sinterability and give a sintered body with a relative density of 100% by sintering at a considerably lower temperature than normal, such as 1750° C. Also WC powders with a large particle size and a wide-size distribution have a high sinterability caused by the presence of fine particles and the sinterability of WC powders is influenced significantly by the sintering atmosphere. The atmospheric effect is discussed in connection with the heating behaviour of a surface oxide layer and free carbon.