Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

TiC based steel bonded carbides with the addition of nano TiN were prepared by vacuum sintering techniques. The microstructure was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanical properties, such as bending strength, impact toughness, hardness, and density, were measured. The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition; several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains. The smaller and larger carbide grains joint firmly, and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition. But the mechanical properties do not increase monotonously with an increase in nano addition. When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides, the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.