Alternative Approach to the Manufacture of Ultrafine Grained Hardmetal Powders

摘要

The manufacture and the final alloy properties of cemented carbides with ultrafine carbide grain size (0.2-0.5 μm) are closely linked to the main constituents: WC and Co powder. Ultrafine hardmetals exploit the benefits of three modern powder production techniques: the dominating APT calcination-reduction-carburisation (CRC) process, the rapid carbothermal reduction (RCR) process and the direct carburisation process. Hardmetal production increasingly demands a uniform ultrafine WC grain size coupled with a homogeneous dispersion of the Co-binder in the sintered microstructure. This enables reduced carbide contiguity and optimization of the hardness/toughness relationship. This paper discusses alternative powder concepts for the manufacture of WC/Co composite powders: co-reduction and carburisation processes. The powder characteristics of such ultrafine composite powders are discussed.