Characterization of hot-pressed ZrC–TiC composites

Abstract

Synthesis and consolidation of (Zr,Ti)C were investigated in the present work. ZrC–TiC powder mixture was synthesized at 1650°C for 90 min by the carbothermal method. The prepared powder mixture was hot-pressed at 1800 C for 60 min under a pressure of 40Mpa and then heat-treated at 2100 C for 60 min. There were ZrC-rich and TiC-rich phases together with zirconium oxide phases in powder mixture and hot-pressed samples, while there were no oxide phases in the heat-treated sample and only ZrC-rich and TiC-rich phases were present in the sample. The FESEM image of the fracture surface of the samples shows that the porosity of the samples decreases with increasing temperature. Relative density, microhardness, and flexural strength increased from 93.8% to 98.6%, from 15.26 to 21.41 GPa, and from 185.02 to 220.69 MPa, respectively, with increasing temperatures from 1800 C to 2100 C. In contrast to these properties, the fracture toughness of the samples was reduced from 3.71 to 3.47 MPa·m^1/2. The investigation of oxidation behavior also showed that oxidation is influenced by oxygen diffusion and exhibits nonlinear behavior as a function of time. With increasing oxidation temperature of hot-pressed and heat-treated samples from 600 to 1000°C, parabolic oxidation rate constants (k_p) increased from .267 to 11.793 and from .367 to 10.993, respectively.