超重力燃烧合成ZTA-TiC-Fe金属陶瓷的高温稳定性

使用超重力燃烧合成技术制备了ZTA-TiC-Fe金属陶瓷复合材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)及变温X射线衍射对金属陶瓷样品的物相组成、微观结构以及升降温过程中材料的微观结构演变行为进行研究。结果表明:利用超重力燃烧合成熔铸方式可直接制备出ZTA-TiC-Fe金属陶瓷;其中t-ZrO2与Al2O3形成的ZTA共晶陶瓷相呈三维网状结构,TiC包覆金属Fe填充于三维ZTA陶瓷骨架中;ZTA-TiC-Fe失效机理:Fe和ZrO2相在750℃左右发生相变;Fe、ZrO2在升降温过程中相变产生的体积变化以及各组分相热膨胀系数不同所引起的内应力释放,导致材料微观结构破坏;有氧环境中,温度超过550℃,表层Fe相的氧化速度加快,生成结构疏松多孔的红褐色Fe2O3。Fe相氧化产生约8倍的体积膨胀,导致三维陶瓷骨架不可逆破裂。

High Temperature Stability of ZTA-TiC-Fe Cermets Synthesized by High Gravity Combustion

ZTA-TiC-Fe cermet composites were prepared by high gravity combustion synthesis technology.X-ray diffraction(XRD),scanning electron microscopy(SEM) and variable temperature X-ray diffraction were used to study the phase composition,micro structure and micro structure evolution of the cermet during heating and cooling process.The results show that ZTA-TiC-Fe cermet can be fabricated directly by high gravity combustion synthesis melting-casting method.The ZTA eutectic ceramics formed by t-ZrO2 and Al2O3 present a three-dimensional network structure,and TiC-coated Fe are filled in the three-dimensional ZTA ceramic skeleton.The inefficacy mechanism of ZTA-TiC-Fe is as follows:the phase transformation of Fe and ZrO2 occurs at about 750℃;the volume changing due to phase transformation of Fe and ZrO2 during heating and cooling and the internal stress release caused by the different thermal expansion coefficients of each component lead to the thermal expansion of the ZTA-TiC-Fe cermet.In the aerobic environment,the oxidation rate of Fe phase in the surface layer increases when the temperature exceeds 550℃,forming porous red-brown Fe2O3.The oxidation of Fe phase produces a volume expansion of about 8 times,resulting in the irreversible rupture of three-dimensional ceramic skeleton.