Effects of MoSi2 additions on the properties of Hf- and Zr-B2 composites produced by pressureless sintering

Composites in the HfB2-(5-20 MoSi2) system were produced from powder mixtures and densified through pressureless sintering at 1950°C. Microstructure and mechanical properties were compared with pressureless sintered ZrB2-based composites containing the same amount of MoSi2. The addition of MoSi2 allowed the achievement of highly dense bodies without degrading the high temperature behaviour. Flexural strength measured at 1500°C in air were in the range of 480-580 MPa