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The FeWB based cermets were produced by the reaction boronizing sintering at different temperature and with different holding time. The influences of temperature and holding time on the phase transformation, microstructure of cermets as well as the reaction mechanism were investigated by X-ray diffraction meter (XRD), scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). The results showed that the hard phase FeWB was produced in the compact at the stage of solid phase sintering by the reaction W + Fe2B = FeWB +Fe and W + FeB = FeWB. Besides, the FeWB phase exhibited an equiaxed morphology. The distinctly rapid densification occurred at the temperature ranging from 800°C to 1150°C while the FeWB phase transformed to Fe7W6 phase, which resulted in the further improvement of the density when the temperature exceeded 1300°C. With an increase of temperature, the cermets prepared by liquid phase sintering exhibited a relatively homogenous microstructure, accompanied by in situ growth of thick FeWB grains. In order to obtain a higher density, the experimental results showed that the sintering temperature of preparing FeWB based cermets should be controlled between 1150°C and 1250°C. Moreover, it was necessary to appropriately increase the content of iron and ferro-boron.