Effects of B2O3 on the Microstructure and Properties of h-BN-ZrO2-SiC Composites

Side seal plates for thin-strip continuous casting require exceptional resistance to thermal shock, corrosion and wear, for which h-BN based ceramics serve as promising candidates. However, h-BN-ZrO 2 -SiC composites suffer from poor sintering densification. h-BN-ZrO 2 -SiC composites modified with varying amounts of B 2 O 3 as a single additive were prepared via vacuum hot-press sintering at 1550 °C, 1600 °C and 1650 °C. The phase composition, microstructure, relative density, flexural strength and thermal shock resistance were systematically investigated. The composite with 1 wt% B 2 O 3 sintered at 1650 °C achieved a flexural strength of 76.6 MPa, which was 42% higher than that of the additive‑free sample. The results revealed that B 2 O 3 facilitates the in-situ formation of ZrB 2 via a liquid‑phase sintering mechanism. This work clarified the modification mechanism of B 2 O 3 in h-BN-based composites, providing experimental basis and theoretical guidance for the development of h‑BN‑based ceramics used for side dams in thin‑strip continuous casting.