Effects of SiC platelet and ZrSi2 additive on sintering and mechanical properties of ZrB2-based ceramics by hot-pressing

Fully dense Zirconium Diboride (ZrB2)-based ceramics with Zirconium Silicide (ZrSi2) and Silicon Carbide platelet (SiCpl) additive were fabricated by hot-press sintering in flowing argon atmosphere. Their mechanical properties and microstructure were examined. The contents of ZrSi2 and SiCpl were optimized. The defined addition of ZrSi2 was beneficial for densification and improving the mechanical properties of the ZrB2-based ceramics. The addition of SiCpl obviously improved the fracture toughness of the ZrB2-based ceramics. The range of fracture toughness of ZrB2–SiCpl–ZrSi2 composite was 6.7–9.0 MPa m1/2. The flexural strength of the composites varied a little and the maximum was 597 MPa when the content of ZrSi2 and SiCpl was both 5 vol.%. XRD results showed that a small amount of Zirconium Carbide (ZrC) formed during sintering. The microstructure of the composites was fine, compact and homogeneous.

► ZrSi2 and SiC platelet (SiCpl) were added together to fabricate ZrB2-based composites by hot-press sintering.
► The flexural strength and fracture toughness of specimen with optimum addition were 597 MPa and 8.98 MPa m1/2.
► The main toughness mechanism was synergistic toughening of different toughness mechanisms.