ZrO2-BN composites with different additives have been fabricated by hot-pressing at 1600°C for 60min in vacuum.The mechanical properties and corrosion resistance of composites have been investigated systematically.The composite with B2O3-Si3N4-CaF2 as additive has excellent mechanical properties.The flexural strength,fractural toughness and Vickers' hardness can reach 307MPa,5.82 MPa·m1/2 and 3.09GPa,respectively.However,the corrosion resistance of composite with B2O3-Si3N4-CaF2 as additive has poor corrosion resistance due to the dissolution of Si3N4 and CaF2 in molten steel.When using B2O3-SiC as additive,the corrosion resistance of composite has been improved effectively and the thickness of corrosion layer is 100μm against 45# steel at 1600°C for 30min.The corroded layer is formed by porosities and remained ZrO2 phase at interface between composite and steel,which as a protective layer to obstruct the infiltration of liquid steel according to the EDS analysis.Meanwhile,a new corrosion patch is produced with the residual porosities when low-molten point phases dissolution in molten steel.The molten steel infiltrates in the corrosion patch and promotes further corrosion of composite by chemical reaction between BN and the dissolved oxygen.
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