Microstructure refinement and mechanical properties improvement of HfB2–SiC composites with the incorporation of HfC

HfB2 and HfB2–10 vol% HfC fine powders were synthesized by carbo/boronthermal reduction of HfO2, which showed high sinterability. Using the as-synthesized powders and commercially available SiC as starting powders, nearly full dense HfB2–20 vol% SiC (HS) and HfB2–8 vol% HfC–20 vol% SiC (HHS) ceramics were obtained by hot pressing at 2000 °C/30 MPa. With the incorporation of HfC, the grain size of HHS was much finer than HS. As well, the fracture toughness and bending strength of HHS (5.09 MPa m1/2, 863 MPa) increased significantly compared with HS (3.95 MPa m1/2, 654 MPa). Therefore, it could be concluded that the incorporation of HfC refined the microstructure and improved the mechanical properties of HfB2–SiC ceramics.