Rapid densification mechanism and properties of h-BN/ZrO2 composites with oxide additives by spark plasma sintering
Mao Chen, Bingbing Fan, Haoyuan Lei, Zijie Song, Shaojun Zhang, Hailong Wang, Rui Zhang, Hongxia Li, Yongqiang Chen
Abstract
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.