Densification and oxidation behavior of a novel TiB2-MoSi2-CrB2 composite

Titanium diboride (TiB2) composite with MoSi2 and CrB2 has been prepared and tested to possess excellent oxidation resistance. Dense composite pellets were fabricated by hot pressing of powder mixtures. Microstructural characterization was carried out by XRD and SEM. Hardness and fracture toughness values were measured. Extensive oxidation studies of the composites were also carried out. Density of >= 96% p(th) was obtained by hot pressing at 1800 degrees C under a pressure of 35 MPa for 1 h. Hardness and fracture toughness were in the range of 18-24 GPa and 35-4 MPa.m(1/2) respectively. Crack branching, deflection and bridging mechanisms were observed in the crack propagation paths. Isothermal and continuous oxidation studies of these composites up to 1000 degrees C showed improved oxidation resistance with the formation of protective glassy layer. TiO2, Cr2O3 and SiO2 phases were identified on the oxidized surface. Diffusion controlled mechanism of oxidation was observed in the composites. (C) 2012 Elsevier Ltd. All rights reserved.