Mechanical properties and oxidation resistance of hafnium carbonitride hot pressed ceramics

In this study, ceramic hafnium carbonitride samples were obtained, consolidated by hot pressing commercial hafnium carbide and nitride powders. Consolidation was performed at a temperature of 2000 °C, a pressure of 40 MPa, and a holding time of 15 min. The mechanical properties of the materials were determined during the study. It was found that during the formation of hafnium carbonitride, increasing the stoichiometric C:N ratio from 20:80 to 80:20 increases the hardness from 17.7 to 22.9 GPa, Young’s modulus from 452 to 479 GPa, and strength from 622 to 694 MPa. In turn, increasing the nitrogen content increases the crack resistance of the material. A study of the oxidation resistance of materials exposed to high temperatures of 1200 °C revealed that hafnium carbonitride samples exhibited increased oxidation resistance compared to hafnium carbide and hafnium nitride samples. As the carbon content in the carbonitride increased, the oxidation rate decreased. Upon heating, parabolic oxidation kinetics were observed. After oxidative exposure, a dense, highly adhesive oxide layer formed on the surface of the samples.