Microstructures and mechanical properties of Mo2FeB2-based cermets prepared by two-step sintering technique

Ternary boride based cermets were prepared by two-step sintering technique. The first pre-coarsening step was short at a relatively high-temperature in order to yield critical density and render pores unstable. The second step at lower temperatures for long holding duration facilitated further densification with limited grain growth occurring by the slower grain-boundary diffusion. It was shown that for fine-grained Mo2FeB2-based cermets, the optimum processing condition included pre-coarsening temperature (T-1) = 1160 degrees C, pre-coarsening duration (t(1)) = 30 min, subsequent sintering temperature (T-2) = 1080 degrees C and (t(2)) = 20 h. The cermets exhibited excellent mechanical properties with the transverse rupture strength of 2139.5 MPa and the hardness of 90.2HRA. Compared to conventional vacuum sintering, the grain size of the cermets prepared by two-step sintering technique was reduced from 1.89 mu m to 1.21 mu m.