Influence of Alternative Hard and Binder Phase Compositions in Hardmetals on Thermophysical and Mechanical Properties

Abstract

Due to the classification of Co as a CMR (carcinogenic, mutagenic, toxic to reproduction) as well as the classification of both Co and WC as CRM (critical raw materials) more and more research is being carried out to investigate possible substitutes for WC-Co hardmetals. To directly compare their microstructure as well as mechanical and thermophysical properties, five very different hardmetals were investigated. For this purpose, the compositions WC-Co, WC-FeNiMn, WC-HEA, NbC-Co and HEC-Co were selected in order to investigate alternative binders for cobalt as well as different alternative hard phases for WC. The results of the hardness measurements showed that for the hardmetals with alternative binders (WC-FeNiMn and WC-HEA) hardness values of 1327 HV10 and 1299 HV10 comparable to WC-Co with 1323 HV10 can be achieved. When WC is replaced by HEC as the hard phase, a significantly higher hardness of 1543 HV10 can be obtained, demonstrating the great potential of high-entropy carbides. Furthermore, the hot hardness measurements between RT and 900 °C showed significantly higher values (up to approx. 290 HV10) for the WC-HEA and HEC-Co hardmetals compared to those of WC-Co. However, the fracture toughness of the alternative hardmetals was lower compared to that of conventional WC-Co hardmetals. In terms of thermophysical properties, the results of the hardmetals with alternative binders were close to those of WC-Co. Thus, it can be shown that it is possible to produce alternative hardmetals with comparable properties to WC-Co and that with further optimization they show great potential to replace WC-Co in the near future.