Composite WC–35% Ni Produced from Ultrafine WC + NiО Powders.
II. Mechanical Properties

Abstract

The mechanical characteristics of ultrafine-grained WC–35 wt.% Ni composite produced by short-term pressing in a solid phase at different temperatures and at pressure ~1200 МPа are studied. The initial powder mixture of the composite consists of tungsten carbide and nickel oxide, but one part of the mixture is reduced in hydrogen and the other part is mixed with saccharose to reduce nickel from oxide 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 samples from a mixture of powders treated in hydrogen have lower transverse rupture strength if the composite is consolidated at temperatures lower than 1250 °С. At this pressing temperature, the samples acquire transverse rupture strength of 2700–2800 МPа irrespective of the mixture preparation procedure. The consolidation of the composite in a liquid phase leads to decrease in strength to 1800 МPа. It is shown that the fracture of the composite densified in the temperature range 950–1150 °С occurs generally along the nickel matrix, which deforms severely before fracture in the composite pressed at 1150 °С. The fracture toughness of the composite densified in a solid phase is 25 МPа • m^1/2 and its hardness is higher than 6000 МPа.