Sintering and Properties of Cobalt-coated Al_2O_3/TiC Composits

The hot-pressing sintering studies were carried out by using mixtures of cobalt coated Al2O3 and TiC micro-size and nano-size powders with different cobalt content at different temperatures.The results show that the sintering effects of nano-size powders is super than micro-size powders.The hardness(HRA),flexure strength and fracture toughness of the composites measured are 92.7,782 MPa and 7.81 MPa·m1/2.Compared the fracture surfaces of three materials prepared by the same technology,the fracture modes of Al2O3 and Al2O3/TiC are intergranular mainly.Thus the fracture surfaces of cobalt coated Al2O3/TiC composites(ATC)is the mixture of intergranular and transgranular.Some phenomenon helpful for improving flexure strength fracture toughness such as intergranular-type structure,the tortuous routes of crack propagation,the crack branching,crack deflecting and bridging are observed on the ATC fracture surface.