Microstructure and properties of an HfB(2)-SiC composite for ultra high temperature applications

The present study deals with an HfB2 matrix composite containing 19 v/o beta-SiC, hot pressed at 1850°C and a pressure of 30 MPa for 20 min. The addition of Si3N4 and SiC proved to be effectiove in improving the sinterability and performance of ZrB2-based materials. Densification behaviour during hot pressing and the microstructure developmenmt were studied. Some mechanical properties (fracture toughness, hardness, thermal expansion, flexural strength up to 1500°C in air) were studied as well. Their behaviour were correlated to the microstruxctural features.