Microstructure, Mechanical Properties and Oxidation Behavior of Reactive Hot-Pressed (Zr,Ti)B2-SiC-ZrC Composites

Reactive hot pressing of an initial powder mixture including ZrB₂, SiC and TiC particles with volume ratio of 75:20:5 was investigated in this study. The sintering process was conducted under 40 MPa uniaxial load at 1850°C for 1 h. The microstructure and mechanical performance of hot-pressed specimen were analyzed using an X-ray diffractometer, scanning electron microscope and Vickers indenter and bending strength tests. The (Zr,Ti)B₂ phase was detected because of the solid solution formation. A relative density of 98.7% was recorded. Additionally, the composite material exhibited a hardness of 19.4 GPa, fracture toughness of 4.5 MPa.m^0.5 and bending strength of 367 MPa. To investigate the oxidation behavior of the composite, several samples were subjected to oxidation at 1000, 1400 and 1700°C for durations of 1 h, 4 h and 10 h, respectively. Utilizing the rates of parabolic oxidation determined for all temperatures, an activation energy of 167.4 kJ/mol was calculated. Microstructural characterization of the section of the sample oxidized for 4 h at 1700°C showed the presence of four distinct layers: (1) porous ZrO₂-rich layer, (2) dense protective SiO₂ and TiO₂ layer, (3) SiC-depleted layer and (4) unaffected section.