FeWB基陶瓷在真空烧结过程中的组织和相转变

研究了烧结温度和保温时间对反应硼化烧结制备FeWB基陶瓷的影响。利用X射线衍射，扫描电镜和能谱仪对FeWB基烧结过程中的相转变，微观组织以及反应机理进行了表征。结果表明FeWB硬质相是通过W + Fe2B = FeWB + Fe和FeB + W = FeWB两种方式合成的，并且反应生成的FeWB晶粒呈各向异性分布。在温度区间为800℃-1150℃之间，FeWB基陶瓷的密度骤然升高，这与Fe2B相的熔化有关。在1300℃时，由于W2B相的存在，会使FeWB相转变为Fe7W6相，从而使密度进一步升高。随着烧结温度的提高，通过液相烧结制备的金属陶瓷表现出相对均匀的微观结构，而且原位合成的FeWB颗粒会发生长大。为了获得较高的致密度，实验结果表明，FeWB基陶瓷的烧结温度应控制在1150℃-1250℃之间。其次，适当的增加铁和硼铁的含量有利于烧结的致密化。

Synthesis and microstructure evolution of FeWB based cermets during the vacuum sintering

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.