Ti(C,N)/Fe-Co-Ni金属陶瓷烧结过程中的结构和相变

Microstructure and Phase Transformation of Ti(C,N)/Fe-Co-Ni Cermets during Sintering Process

在不同温度下采用真空烧结、X射线衍射(XRD)和背散射扫描电镜(BSE-SEM)研究了Ti(C_(0.7)N_(0.3))-WC-Mo_2C-TaC-Fe/Co/Ni体系金属陶瓷在烧结过程中的微观结构和相转变规律。研究结果表明,在1000℃以后WC相突然消失,显微组织中出现大量白色絮状析出相,其为固相烧结阶段形成与环形相成分相似的(W,Ti,Mo,Fe)C固溶体,并且大量的M_(12)C型η_2相存在于合金烧结体中。在1200℃以后Mo_2C,TaC和η_2相消失,随着温度的变化,合金中η相的种类及其含量发生变化。在1250℃以后M_(12)C型η相逐渐转变为M6N型脆性相,且高Fe含量粘结相的存在促进了M6N型脆性相的生成。在1410℃以后,原子扩散和溶解-析出过程更为充分,环形相厚度增加,且组织中析出了亮芯灰环结构,M_6N型脆性相减弱至逐渐消失,因此可以认为脆性相是在烧结的初期阶段形成但是随着烧结的进行而逐渐溶解消失。

Using X-ray diffraction（ XRD）, back scattered scanning electron microscope （BSSEM） and vacuum sintering at different temperatures, the microstructure and phase transformation rules of Ti（ Co7 No3 ）-WC-Mo2C-TaC-Fe/Co/Ni system cermets during sin- tering process were studied. The results showed that WC phase suddenly disappeared after 1000℃, many white flocculent precipitated phase existed inside the microstructures, which was （W, Ti, Mo, Fe）C solid solution that formed during solid-phase sintering stage. Its chemical composition was similar to that of the rim phase, and a large number of Ml2 C-type℃ phases appeared in the sintered body. The Mo2 C, TaG and η2 phase disappeared after 1200℃, and with the change of sintering temperature, species and content of η phase in the alloy would also alter. The M12C-type η phase was transformed to M6N-type brittle phase above 1250℃, and higher Fe concentration in binder would promote the formation of M6N-type brittle phase. Above 1410℃, atomic diffusion and dissolution-pre- cipitation process was more effective, the thickness of rim phase increased, and bright core-grey rim structure phase was precipitated. In addition, the M6 N-type brittle phase gradually decreased and then disappeared in the alloy. Therefore, it could be concluded that the brittle phase was formed in the early stages of sintering, and then gradually dissolved and disappeared during sintering process.