Effect of ZrO2 on sintering behavior and properties of h-BN/ZrO2 composites by spark plasma sintering

The h-BN/ZrO 2 composites with different 3Y–ZrO 2 content were prepared by spark plasma sintering at 1800 °C. The sintering behavior , bulk density, apparent porosity , thermal conductivity , thermal expansion coefficient , bending strength , thermal shock resistance , microstructure and phase were analyzed. The optimum specimens were used to test the resistance to corrosion of molten steel for 10, 20, 40, 80 min respectively. The results indicated that ZrO 2 could facilitate the sintering process of h-BN matrix under the action of spark plasma. Especially, for the composites with 30 wt% 3Y–ZrO 2 , the porosity could decrease to 1.1% and the flexural strength could exceed 150 MPa. The microstructure showed the h-BN grains and 3Y–ZrO 2 grains are closely combined. The XRD patterns indicated that the t-ZrO 2 diffraction peak gradually enhanced with the increase of density. With the increase of erosion time, the erosion rate increased significantly. After the surface of the specimen is eroded, the erosion resistance of the matrix would decrease significantly. This h-BN/ZrO 2 could be as side-dam used in the thin strip continuous casting process .