Rapid densification mechanism and properties of h-BN/ZrO2 composites with oxide additives by spark plasma sintering

Large size high density h-BN/ZrO 2 composites (ø = 110 mm, h = 15 mm) were rapidly prepared by spark plasma sintering (SPS) with sintering cycle 20 min. The effects of additives on the mechanical properties , microstructure evolution, and corrosion resistance of the h-BN/ZrO 2 composites were studied. The Al 2 O 3 , MgO , SiO 2 , La 2 O 3 and ZrO 2 rapidly formed heterogeneous eutectic crystals under the action of SPS. The low eutectic compounds significantly promoted the diffusion of h-BN or ZrO 2 , also increased the density. The flexural strength of h-BN/ZrO 2 composites could reach 196.31 MPa, and the apparent porosity was only 0.42 %. The additives are combined with zirconia to form a high viscosity eutectic, whose corrosion resistance to molten steel is obviously better than that of single ZrO 2 . The corrosion depth of h-BN/ZrO 2 composites was only 114 µm after corroded in molten steel at 1550 °C for 80 min. The comprehensive properties of h-BN/ZrO 2 composites were obviously improved by appropriate additives.