The effect of boron-doped cobalt additions on mechanical properties of a recycled WC-Co powder

Abstract

Cobalt and tungsten have been listed since 2008 as “critical raw materials” by the European Commission. Recycling used cemented carbide tools is a solution to reduce the criticality of those materials. However, recycled tungsten carbide powder, made from the Coldstream process, shows low sinterability properties at conventional sintering temperatures. To enhance mechanical properties, boron-doped cobalt powder is added during the ball milling step. Due to the formation of a eutectic between boron and cobalt, the sinterability of the powders is greatly improved, and the sintering temperature could be decreased by 100 °C compared to conventional processes.The as-received recycled powder contains 7.5 wt% cobalt. That powder has been milled with the addition of boron-doped cobalt powder. Three powders have thus been prepared: WC-7.5(CoB), WC-10(CoB), and WC-15(CoB). The sintered parts have been characterized in terms of physical, and mechanical properties, and grain size distributions. The boron-doped parts showed superior mechanical properties for a lower sintering temperature than boron-free samples.