Effects of SiC on densification, microstructure and nano-indentation properties of ZrB₂–BN composites

Introducing the SiC additive resulted in a noticeable enhancement in the sintering behavior of the ZrB₂–hBN composite, profiting from the SiC involvement in the surface oxide removal. This research intended to compare two ceramics of ZrB₂–hBN and ZrB₂–SiC–hBN in terms of sinterability, microstructure, and mechanical features. Both samples were spark plasma sintered at 2000 °C for 5 min under 30 MPa. The SiC-free specimen reached a relative density of lower than 95%, while incorporating SiC improved this value up to 99.3%, resulting in near fully dense material. The role of SiC on oxide removal was found to be the chief cause in enhancing the sinterability of the ZrB₂–SiC–hBN sample compared to ZrB₂–hBN. According to the field emission scanning electron microscopy (FESEM), field emission-electron probe microanalyzer (FE-EPMA), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS) studies, both systems were unreactive, and no major in-situ phase could be produced over the sintering process. The ZrB₂–SiC–hBN composite reached an elastic modulus of 374 GPa and a Vickers hardness of 19 GPa.