Pressureless liquid-phase sintered TiCX-NiTi/Ni cermets

TiC0.7-NiTi and TiC0.95-Ni cermets with 10, 20 and 30 vol% binder content were prepared by pressureless liquid-phase sintering. The shrinkage behavior and liquid forming temperature of TiC0.7-NiTi powder compacts were investigated to determine the optimum sintering temperature (1380 degrees C) and dwell time (60 min). The microstructure of the sintered cermets was characterized and correlated to the measured mechanical properties (hardness, fracture toughness, strength and E-modulus). The TiCx stoichiometry of the TiC0.7-NiTi cermets was modified by the addition of TiH2 powder to the TiC0.95+Ni49.4Ti50.6 starting powder mixture, and a pure austenite NiTi binder phase was obtained. The carbide and binder phase displayed a homogeneous elemental distribution in the TiC0.7-NiTi and TiC0.95-Ni cermets. The differences in grain size, contiguity and binder mean free path length of the TiC0.7-NiTi and TiC0.95-Ni cermets were correlated to the measured wetting angle between binder and carbide phases at 1380 degrees C. The Ni binder showed a brittle fracture, whereas the NiTi binder fractured in a ductile way. The hardness and E-modulus of the TiC0.7-NiTi cermets were lower than for the corresponding TiC0.95-Ni equivalent, whereas the fracture toughness and bending strength were significantly higher.