Novel binders for WC-based cemented carbides with high Cr contents

Substitution of Co as binder in cemented carbides has led to the study of a wide range of alternatives. Researchers look for novel binders that can provide similar characteristics as those found in WC-Co alloys, and also systems that can improve certain characteristics such as the oxidation and corrosion resistance or high temperature properties. Some of the binder systems proposed contain rather high Cr in their composition; like in cemented carbides prepared from stainless steel powders, or from certain High Entropy Alloys (HEA). However, phase formation in such systems is often not well described, in particular with regard to the formation of Cr-rich carbides. This work presents an overview on the phase formation in cemented carbides prepared from different Cr-rich binders, providing both experimental studies and thermodynamic calculations. The results show how additions of Cr above a certain limit (mainly determined by its maximum solubility in the binder) lead to the formation of Cr-containing carbides at all carbon contents. As a consequence, no classical two phase area -containing only WC and metallic binder-can be expected in these systems. Due to the formation of Cr-rich carbides, the composition of the metallic binder after sintering can change dramatically, and the amount of metallic binder can decrease significantly. As a consequence, the final properties might not meet the expectations.