Kozo Kitamura

Development of new WC–Ni hardmetals for use in high pressure experiments

Ultrafine-grained (0.2–0.3 µm) WC–Ni hardmetals with a low Ni content (3–5 wt%) were developed using new production techniques based on adding an appropriate amount of VC and Cr3C2, combined with the strong mixing of raw materials. Their uniaxial compressibility was subsequently compared with that of existing WC–Ni and WC–Co hardmetals to assess their suitability for use as anvils in various high pressure experiments, particularly those associated with neutron or magnetic studies. The ultimate compressive strength of the newly developed hardmetals was over 7.7 GPa, which was higher by 1.2 GPa than that of the existing WC–Ni hardmetal ‘MF10’. When these hardmetals were used as anvils, a pressure of approximately 16 GPa was generated using a Paris-Edinburgh-type apparatus with φ8 mm culet, thereby proving that they can allow the physical properties of various materials to be measured at higher pressures than is possible with existing hardmetals.

Structure Change Appearing around Vickers Hardness Indentation on TiC-based Cermets at High Temperature

It was found that the binder phase frequently appeared around Vickers hardness indentation (V.H.I.) to form dotted structure of binder in TiC-based cermets at high temperature, and this phenomenon was never found in WC-based cemented carbides. Then the present study as to the phenomenon was carried out using TiC-(0, 20) vol%TiN-20 vol%Mo2C-(5-20) vol%%Ni cermets in relation to the alloy composition, structure and hardness testing conditions. It was made clear that the appearance of the binder phase was influenced by the factors mentioned above, and also caused by the fact that the plastic flow of the binder phase under compressive stress due to V. H. I. occurred more easily than that of the alloy, depending on the alloy structures, testing temperatures, etc.