Effect of co-addition of WC and MoSi₂ on the microstructure of ZrB₂–SiC–Si composites

In this paper, ZrB₂–SiC–Si-based ceramic composites with WC and MoSi₂ additives were fabricated using SPS method and their densification behavior was investigated by phase and microstructural studies. During the SPS process and according to the prevailing conditions, WC and MoSi₂ additives reacted with the surface oxide impurities of the main raw materials. As a result of these reactions and the decomposition of some raw materials, a series of oxide liquid phases formed, which were often Si-based, and due to their good fluidity, undissolved and free elements such as Zr, Mo and W moved to open porosities and grain boundaries. According to the established thermodynamic conditions, binary solid solutions and new phases such as MoB, ZrC and WB formed. The synthesis of such phases boosted the densification of the composites due to the fact that they formed in porosities or voids between the main grains. The results showed that the sample doped with 2.5 vol% WC and 2.5 vol% MoSi₂ had the highest relative density (about 99%). Meanwhile, microstructural studies showed that homogeneous and dense parts can be achieved by SPS technology.