Development Of Ti(C, N)-based Nano-composite Cermet Die Material

Recently, die is one of the important equipments needed in modern industry. But the working condition of die is extremely harsh, for instance the unit extrusion pressure of cold extrusion is up to 2000MPa. So some phenomena often happen such as soldering, oxidation and even welding in the extrusion process, leading to the intensifying of wear and reduction of service life because of the friction between die and workpiece. Therefore, the major way of improving die service life is to select the materials with better wear resistance and higher hardness. From the performance requirement of cermet die materials, a new Ti(C,N)-based nano-composite cermet die material with better comprehensive mechanical properties was prepared by hot pressing technique under vacuum atmosphere. The correlations among the material composion, the microstrures, the hot pressing process technique and comprehensive mechanical properties were investigated. Then, the strengthening and toughening mechanism of the Ti(C,N)-based nano-composite cermets die material has been systematically investigated. Meanwhile, the friction and wear behaviors of the Ti(C,N)-based nano-composite cermets die material has been studied in detail.The influence of nano-ZrO₂ and micro-WC on the microstructure and mechanical properties of Ti(C,N)-based nano-composite cermets die material has been discussed, then the hot press sintering was optimized. Ti(C,N)-based nano-composite cermets die material were fabricated successfully with better comprehensive mechanical properties. Its flexural strength, fracture toughness and hardness is 1144MPa, 8.60MPa·m^1/2 and 14.57GPa, respectively. Although the hardness is slightly decreased, the flexural strength and fracture toughness is nearly 16.73% and 40.07% higher than that of the cermet without any addition of nano-ZrO₂ and micro-WC. It is found that grain-refining trend and inter/trans mixed fracture mode happens with adidtion of nano-ZrO₂. Morever, some strengthening and toughening mechanisms, such as crack bridging, crack deflection and branching has improved the comprehensive mechanical properties of Ti(C,N)-based nano-composite cermet die material.The friction and wear mechanisms of Ti(C,N)-based nano-composite cermets Die Material were investgated by the scanning electron microscopy and X-ray diffraction on the wearing sample of Ti(C,N)-based nano-composite cermets die material.Meanwhile, the friction and wear behaviors of the Ti(C,N)-based nano-composite cermets die material has been studied, its dominant wear mechanisms are abrasive wear, oxidative wear and adhesive wear, while the dominant wear mechanisms of Ti(C,N)-based cermet die material are grain stripping and brittle fracture. At last, a primary process validation of die manufacture was done.