Effect of Added Cr_3C_2 on the Microstructure and Mechanical Properties of WC-SiC Ceramics

摘要

WC-20 mol% SiC ceramics with added Cr_3C_2 were sintered at 1600°C with a resistance-heated hot-pressing machine. Dense WC-SiC ceramics containing 0.1-0.9 mol% Cr_3C_2 were obtained. Above 1.2 mol% Cr_3C_2,the relative density decreased with increasing CY3C2 content. A small amount of a Nowotny-phase-type (Mo_5Si_3C-type) product was formed by the addition of Cr_3C_2 , and no Cr_3C_2 -based solid solution was found. The WC-20 mol% SiC-Cr_3C_2 ceramics had very fine equiaxed granular WC grains because of inhibited grain growth of WC. The Young's modulus of the WC-20 mol% SiC-Cr_3C_2 ceramics decreased with increasing Cr_3C_2 content because Cr_3C_2 has a much lower Young's modulus than WC. Cr_3C_2 addition below 0.9 mol% increased the Vickers hardness from 20.9 to 23.0 GPa, but a larger added amount reduced the Vickers hardness. The hardness of the WC-20 mol% SiC-Cr_3C_2 ceramics and the WC grain size obeyed a Hall-Petch-like relationship, suggesting that the hardness was strongly controlled by the WC grain size. A higher fracture toughness, 6.4 MPa m , was obtained for the ceramics containing a small amount of Cr_3C_2 than for the binder-free WC. The addition of 0.1-0.3 mol% Cr_3C_2 improved the fracture toughness without reducing the hardness.