Effects of AlN addition on the reactive sintering behavior and comprehensive properties of h-BN/ZrO2 composites prepared by spark plasma sintering

• Reaction sintering significantly promoted the densification of h-BN/ZrO 2 composites, and ZrN played an important role in resisting molten steel corrosion as one of the reaction products. • During the molten steel corrosion process, ZrN consumed a portion of [O] in the molten steel and the newly generated ZrO 2 filled the pores in the matrix. • The corrosion depth of h-BN/ZrO 2 composite was only 69 μm after corroded in molten steel at 1600 °C for 2 h. The h-BN/ZrO 2 composites for preparing ceramic side sealing plate were obtained with spark plasma sintering (SPS) at 1700 °C for 10 min in the study. By varying AlN content from 0 to 20 wt%, we systematically explored its influence on sintering behavior, microstructure evolution, mechanical performance, and corrosion mechanism at1600 °C. Results show that the rapid heating and uniaxial pressure during SPS and the in-situ reactions between AlN and ZrO 2 promoted the densification of composites. The main reaction products were ZrN, which acted as an effective oxygen scavenger, consuming dissolved oxygen ([O]) and converting into ZrO 2 . These newly formed ZrO 2 particles filled residual porosity within the matrix and nucleated around pre-existing ZrO 2 grains, progressively coalescing into continuous Zr-rich barrier layer.Thereby preventing molten steel from further penetrating into the matrix. The corrosion depth of the composite with 5 wt% AlN content in molten steel at 1600 °C after 2 h was only 69 μm. Meanwhile, it showed a thermal conductivity of 25 W m −1 K −1 and a coefficient of thermal expansion of 3.7 × 10 -6 K −1 , demonstrating excellent thermal shock resistance. The composites are expected to be used to manufacture side sealing plates for the novel continuous casting of thin strip.