Study on Binderless Cemented Carbides and Their Related High-Temperature Reactions between Different Phases

Abstract

This paper reviews the investigations carried out in the author’s laboratory for developing of new-type binderless cemented carbides. WC-WB, WC-SiC, and WC-MoC composites were prepared by using resistance-heated hot-pressing (called spark-plasma sintering), and the sinterability, microstructure, and mechanical properties and carbide addition effects on them were mainly examined for application as binderless cemented carbides. WC-SiC had the best sinterability, but the SiC addition induced hardness decrease due to the abnormal growth of WC grains. The abnormal grain growth was prohibited by the addition of small amounts of Cr₃C₂ and/or V₈C₇. WC-MoC composites were prepared by reaction sintering of WC, C, and Mo₂C powder mixtures accompanied by the solid-state reaction (1 − x)WC + x/2Mo₂C + x/2WC → W_1−xMo_xC during sintering. This reaction was accelerated by SiC addition. Carbon addition to WC greatly influenced the grain growth of WC. Carbon nonstoichiometry generated by carbide addition is discussed on the basis of the phase diagram of the added carbide-WC system.