Low-temperature and ultrafast dual-powder spark plasma sintering of (W,Ti)C cermets with the addition of metal core-shell nanopowder

Abstract

Nickel-coated molybdenum metal core-shell (Mo@Ni) nanopowder was prepared by a heterogeneous nucleation–thermal reduction method and then used as the metal binder phase in (W,Ti)C ceramic materials. (W,Ti)C/Mo@Ni/Co cermet was prepared by dual-power spark plasma sintering. The effects of sintering rate and sintering temperature on the microstructure and mechanical properties of (W,Ti)C/Mo@Ni/Co cermets were investigated. Results showed that when the sintering rate was 400 °C/min and the sintering temperature was 1325 °C, the (W,Ti)C/Mo@Ni/Co tool material had the best comprehensive mechanical properties, with a Vickers hardness of 17.44 ± 0.23 GPa, a fracture toughness of 11.27 ± 0.46 MPa·m1/2, and a flexural strength of 1450.23 ± 23 MPa. The core-shell structure of Mo@Ni made full use of the solid solution characteristics of the MoNi binary alloy and produced a solid solution in situ without liquid phase diffusion, which accelerated the sintering rate. The use of Mo nanopowder took advantage of its small-size effects and high surface energy, which reduced the temperature at which the solid solution effect began and reduced the sintering temperature. The combination of these two aspects was used to prepare a (W,Ti)C cermet with good strength and toughness by low-temperature rapid sintering. Low-temperature and ultrafast sintering are helpful to reduce the energy consumption in the preparation of cermets.