Study On Pressureless Sintering Processes Of TiB₂-TiC And TiB₂-TiN Composites

Based on pressureless sintering and lower densification temperature of eutecticcomponent material, TiB2-TiC and TiB2-TiN composites are designed. Theirdensities?microstructure and mechanical properties, together with the effections byadditives and sintering temperature, have been systematically studied by X-raydiffraction(XRD), scanning electron microscopy(SEM), energy dispersivespectroscopy(EDS), X-Ray fluorescence(XRF), Vickers hardness and indentationfracture method. Also, the densification behaviors of sintering have been studied.To TiB2-TiC composite, the influence of ZrO2is positive correlated to thecarbon content in raw materials. The addition of WC does not promote thedensification, but do inhibite the grain growth. Different crafts determined differentmechanical properties, and the greatest Vickers hardness and toughness of thehighest maximum reach to19.1GPa and4.3MPa·m1/2, respectively. Also, therelation between singtering tempetature and relative densiye as well as grain sizehas been analysed.To TiB2-TiN composite, ZrO2can improve the densification greatly and thegrowth of grains, which is quite different from the composite without addtives.High density, as well as microstructure with plate-like TiB2grains, comes from thereaction between ZrO2and free [N]?which promotes the diffusion of Zr atoms.Single WC does not work, but when together with ZrO2, the microstructure ischanged. The diffusion of W, which is promoted by the reaction between ZrO2andWC, is the reason for the appearance core-rim structure of TiB2phase. The greatestVickers hardness and toughness of the highest maximum reach to18.6GPa and4.4MPa·m1/2, respectively. Also, the influerence of nitrogen, which is released by TiNduring sintering, has been studied.