Synthesis and microstructure evolution during vacuum sintering of Mo2FeB2 based cermets

Mo2FeB2 based cermets were prepared by vacuum sintering at different temperatures and with different holding times. The phase transformation and microstructure evolution were studied by using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). It was found that the hard phase Mo2FeB2 was produced in the compact at the stage of solid phase sintering by the reaction Mo and Fe2B, which exhibited an equiaxed morphology. An extremely rapid densification occurred in the temperature ranging from 1050 °C to 1080 °C, and almost full densification was obtained at the temperature of 1080 °C without holding time. With an increase of liquid phase sintering temperature, the cermets exhibited a relatively homogenous microstructure, accompanied by an in situ growth of elongated Mo2FeB2 grains. Abnormally large and faceted Mo2FeB2 grains occurred during the isothermal hold at 1320 °C. These abnormal grains usually coalesced with surrounding grains and grain boundaries were formed between them.