Pressureless sintering of HfB2–SiC ceramics doped with WC

Using WC as sintering aid, nearly full dense (∼99%) HfB2–20 vol% SiC ceramics were sintered at 2200 °C for 2 h without external pressure. The densification mechanism, microstructure evolution, mechanical properties and oxidation resistance were investigated. The results indicated that complex chemical reactions of WC in HfB2–SiC system strongly related to the densification, microstructure and properties. The Young's modulus, fracture toughness and 3-pt bending strength of HfB2–20 vol% SiC with 10 wt% WC were 511 GPa, 4.85 Mpa m1/2 and 563 MPa, respectively, which were comparable to some hot pressed HfB2–SiC ceramics in literature. The oxidation of HfB2–20 vol% SiC with 10 wt% WC at 1500 °C in air exhibited parabolic kinetics. After oxidation at 1500 °C for 10 h, its weight gain and SiC-depleted layer thickness were 3.7 mg/cm2 and 43 μm, respectively, and its residual flexural strength was comparable to or even a little higher than the value before oxidation.