Pressureless sintering of HfB2–SiC ceramics doped with WC

Abstract: Using WC as sintering aid, nearly full dense (∼99%) HfB2–20vol% SiC ceramics were sintered at 2200°C for 2h 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 HfB2–20vol% SiC with 10wt% WC were 511GPa, 4.85Mpam1/2 and 563MPa, respectively, which were comparable to some hot pressed HfB2–SiC ceramics in literature. The oxidation of HfB2–20vol% SiC with 10wt% WC at 1500°C in air exhibited parabolic kinetics. After oxidation at 1500°C for 10h, its weight gain and SiC-depleted layer thickness were 3.7mg/cm2 and 43μm, respectively, and its residual flexural strength was comparable to or even a little higher than the value before oxidation. [Copyright &y& Elsevier]