Role of Si۳N۴ on microstructure and hardness of hot-pressed ZrB۲−SiC composites

The impact of Si۳N۴ content on the hardness and microstructural developments of ZrB۲-SiC material has been investigated thoroughly in the present investigation. Having prepared the raw materials in a jar mill, the ZrB۲-SiC samples containing various amounts of Si۳N۴ were hot-pressed at ۱۸۵۰ °C. Furthermore, XRD, FESEM, and HRTEM were utilized to evaluate the microstructure of samples. The formation of in-situ h-BN was proved by the mentioned methods. Also, it was shown that the Vickers hardness of ZrB۲-SiC increases up to ۲۰ GPa in presence of ۴.۵ wt% Si۳N۴ which is ۳ GPa more than the sample without Si۳N۴. Results show that the positive effect of increased relative density on hardness is more than the negative effect of h-BN soft phase formation.

Keywords:

Hot-pressing , ZrB۲-SiC-Si۳N۴ , Microstructure , Hardness