Design of cobalt gradient via controlling carbon content and WC grain size in liquid-phase-sintered WC–Co composite

WC–Co composites with a gradient of cobalt content can offer an improved performance as a cutting tool. During liquid phase sintering, a Co gradient can be created through Co redistribution induced by pre-designed gradients of WC grain size and/or C content in green parts. The driving force of Co redistribution is migration pressure, which is dependent of three factors – liquid Co volume fraction, WC grain size, and C content. In order to obtain a desired Co gradient, it is necessary to quantitatively understand the dependence of migration pressure as a function of the three factors. This study experimentally established the dependence of migration pressure as a function of C content and liquid Co volume fraction. Combining this result with the previously obtained dependence on WC grain size and liquid Co volume fraction enables the design of Co gradient via controlling carbon content and WC grain size.