Composite WC–35% Ni produced from ultrafine WC + NiO powders. II. mechanical properties

The mechanical characteristics of ultrafine-grained WC–35 wt.% Ni composite produced by shortterm solid-phase pressing at different temperatures and at a pressure of ~1200 MPa are studied. The initial powder mixture consists of tungsten carbide and nickel oxide. One part of the mixture was reduced by hydrogen, while the other part was mixed with saccharose to reduce the oxide to nickel during heating of green briquettes. In the latter case, the synthesis of the metal phase and the consolidation of the WC–Ni mixture proceed in one stage. It is established that the powder mixture samples treated by hydrogen have lower bending strength if the composite is consolidated at temperatures below 1250°C. At this temperature, the samples acquire a bending strength of 2700–2800 MPa, irrespective of how the mixture was prepared. The liquid-phase consolidation of the composite leads to a decrease in the strength to 1800 MPa. It is shown that the fracture of the composite consolidated in the temperature range 950–1150°C occurs generally in the nickel matrix, which deforms severely before fracture in the composite pressed at 1150°C. The fracture toughness of the solid-phase compacted composite is ≥25 MPa ⋅ m^1/2 and its hardness is higher than 6000 MPa.