Microstructure and properties of pressureless sintered ZrC-based materials

ZrC-based composites were produced by pressureless sintering thanks to the addition of MoSi₂ as sintering aid. After preliminary tests, a baseline ZrC material and two mixed ZrC–HfC and ZrC–ZrB₂ composites with 20 vol% MoSi₂ were densified at 1900 to 1950 °C reaching final relative densities of 96%–98%. Mean particle size of the dense bodies ranged from 5 to 9 μm. Secondary phases were found to form during sintering, such as SiC and Zr–Mo–Si-based compounds. Room-temperature mechanical properties were in the range of the values reported in the literature for similar materials densified by pressure-assisted techniques. The flexural strength was tested at room temperature, 1200 and 1500 °C.