Microstructures and Mechanical Properties of (Ti<SUB>0.8</SUB>Mo<SUB>0.2</SUB>)C-30 mass% Ni without Core-Rim Structure

Abstract

Mechanically alloyed powders having the composition (Ti 0:8 Mo 0:2 )C-30 mass% Ni were sintered at 1723 K for 2, 3, and 6 h. After sintering, a TiC phase without a core-rim structure and a Ni phase appeared. In addition, the X-ray diffraction spectrum of 6 h sintered compact showed a Mo peak. With an increase in the sintering time, the hard phase grain size, mean free path of the binder phase, and the binder phase volume fraction increased. The transverse rupture strength and Vickers hardness of the sintered compacts were measured. The maximum average transverse rupture strength was 1.51 GPa for 3-h sintered compact. The relationship between the hardness and the microstructure could be explained by the composite law including the structural factors. 2-h sintered compact had the highest hardness because of the relatively short mean free path of binder phase. 6-h sintered compact had the largest grain size, lowest volume fraction of the hard phase, and the longest mean free path of binder phase. However, this compact was harder than 3-h sintered compact because of the significantly high hard phase contiguity.