WC-(Ti,W)C-(Ta,Nb)C-Co试样烧结过程中组织结构的变化

Microstructure Transformation of WC-(Ti,W)C-(Ta,Nb)C-Co Sample during Sintering Process

将成分为WC-5%（Ti,W）C-5%（Ta,Nb）C-6%Co的混合料在1 150、1 200、1 250、1 300、1 350、1 400、1 450℃不同的温度下烧结,保温30 min制备成烧结体。利用X射线衍射仪、扫描电镜及能谱仪研究各温度下烧结体的相成分和组织结构变化。研究结果表明：当烧结温度为1 150℃时,烧结体中存在四种物相：白色的WC,浅灰色的（Ta,Nb）C,深灰色棱角分明的（Ti,W）C和深灰色的Co相。当烧结温度升高到1 200℃时,（Ti,W）C和（Ta,Nb）C发生轻微的固溶反应形成（W,Ti,Ta,Nb）C相,WC向（Ti,W）C中扩散形成W含量更多的（Ti,W）C相。当温度升高到1 250℃时,（Ti,W）C相几乎消失,（Ta,Nb）C相进一步减少,形成大量的成分不均匀的（W,Ti,Ta,Nb）C相。当温度升高到1 300℃时,（W,Ti,Ta,Nb）C相的成分均匀化过程基本完成。当温度升高到1 350~1 450℃时,WC晶粒进一步长粗,烧结体中存在三个稳定的相：WC、（W,Ti,Ta,Nb）C、γ。

The sintered body with composition of WC-5%（Ti,W）C-5%（Ta,Nb）C-6%Co（mass fraction） was prepared by sintering the powder mixture at 1 150、1 200、1 250、1 300、1 350、1 400、1 450 ℃ for thirty minutes. The transformations of phase and microstructure were studied by using X-ray diffraction and SEM-EDS. The results show that when the sintering temperature is 1 150 ℃, there are four kinds of phases in the sintered body including white WC, light grey（Ta,Nb）C, dark grey angular（Ti,W）C and dark gray Co. When sintered at 1 200 ℃, minor（W,Ti,Ta,Nb）C phase is formed by reaction of（Ti,W）C and（Ta,Nb）C solid solution, and（Ti,W）C phase with more W content is formed by diffusion of WC to（Ti,W）C.When sintered at 1 250 ℃,（Ti,W）C phase almost disappears and（Ta,Nb）C phase decreases further, meanwhile a largenumber of heterogeneous（W,Ti,Ta,Nb）C phase forms. When sintered at 1 300 ℃,the composition homogenization process of（W,Ti,Ta,Nb）C phase is finished. When sintered at 1 350~1 450 ℃, WC grain grows and three stable phases are formed in the sintered body including WC,（W,Ti,Ta,Nb）C and γ.