On the hardness of submicrometer-sized WC-Co materials

The hardness-composition-grain size relationships of cemented WC-Co with WC particle sizes in the submicrometer range have been investigated. It is found that the Hall-Petch relations for individual WC and Co phases derived from micrometer-sized WC-Co are still applicable to submicrometer-sized WC-Co, suggesting that the deformation mechanism remains the same when WC particle sizes change from micrometers to submicrometers. However, the measured hardness of submicrometer-sized WC-Co is lower than that predicted using the equation derived from micrometer-sized WC-Co and the principle that the applied loads are transmitted through the carbide skeleton and the continuous binder phase (Lee and Gurland (1978) [7]). It is proposed that this discrepancy can be addressed by the reduced continuity of WC when WC particle sizes decrease from micrometers to submicrometers at a given WC volume fraction.