Microstructure and mechanical properties of Al2O3-TiC-4vol.%Co composites prepared from cobalt coated powders

Al2O3-TiC-4vol.%Co composite was fabricated by hot pressing cobalt-coated Al2O3 and TiC powders. A chemical electroless method for cobalt deposition on the surface of ceramic powders was used. Microstructure and mechanical properties of the Al2O3-TiC-4vol.%Co composite were compared with that of conventional Al2O3-TiC composite. Cobalt phase was uniformly dispersed in the matrix, especially along the interfaces between Al2O3 and TiC grains, which inhibited the grain growth of the matrix. The fracture mode changed from intergranular to a mixture of intergranular and transgranular type. Overall improvement in fracture toughness (7.8 +/- 0.8 Mpa m(1/2)) and bending strength (782 +/- 60 Mpa) was obtained in the composite, which should be attributed to the improved crack bridging and crack deflection after interfacial modification. And no obvious decrease in hardness was found in the Al2O3-TiC-4vol.%Co composite. The sinterability, homogeneity and fracture behavior appear to be significantly improved due to the application of cobalt coated powders. (c) 2005 Elsevier B.V. All rights reserved.