Pressureless sintering of HfB2-SiC ceramics doped with WC

Using WC as sintering aid, nearly full dense (similar to 99%) HfB2-20 vol% SiC ceramics were sintered at 2200 degrees 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 m(1/2) 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 degrees C in air exhibited parabolic kinetics. After oxidation at 1500 degrees C for 10 h, its weight gain and SiC-depleted layer thickness were 3.7 mg/cm(2) and 43 mu m respectively, and its residual flexural strength was comparable to or even a little higher than the value before oxidation. (c) 2012 Elsevier Ltd. All rights reserved.