Mechanical behavior of zirconium diboride-silicon carbide-boron carbide ceramics up to 2200 °C

The mechanical properties of hot pressed zirconium diboride-silicon carbide-boron carbide (ZrB2-SiC-B4C) ceramics were characterized from room temperature up to 2200 degrees C in an argon atmosphere. The average ZrB2 grain size was 3.0 mu m. The SiC particles segregated into clusters, and the largest clusters were >30 mu m in diameter. The room temperature flexural strength was 700 MPa, decreasing to 540 MPa at 1800 degrees C and to 260 MPa at 2200 degrees C. The strength was controlled by the SiC cluster size up to 1800 degrees C. At higher temperatures, strength was controlled by formation of liquid phases, and precipitation of large BN and B-O-C-N inclusions. The mechanical behavior of these materials changes at similar to 1800 degrees C, meaning that extrapolation of properties from lower temperatures is not accurate. Mechanical behavior in the ultra-high temperature regime was dominated by impurities and changes in microstructure. Therefore, the use of higher purity materials could lead to significant improvements in ultra-high temperature strength. (C) 2014 Elsevier Ltd. All rights reserved.