Microwave Sintering Technology And Properties Of Ultra-fine Ticn Matrix Cermets

Because of their high hardness, excellent wear resistance, red-hardness, thermal conductivity, chemical stability and bond resisitance ability, TiCN matrix cermets are considered as an extremely potential cutting material. In this paper, the ultra-fine TiCN powders were prepared by ball milling method. The size distribution of TiCN particles milled for different times was tested and the effect of ball-powders ratio and milling time on the average particle size of TiCN powders was analyzed. Ultra-fine TiCN matrix cermets reforced by nano-particle were prepared by a microwave sintering. The effect of sintering temperature, holding time and the addition of nanoparticle on the microstructure and mechanical properties of ultra-fine TiCN matrix cermets were studied. Simultaneously, both the micrographs of TiCN powders and the microstructures and distribution of elements of fracture surface of ultra-fine TiCN matrix cermets and their nanocomposite cermets were observed and investigated by scanning electron microscope (SEM) with EDS. The results are shown as follows:1.The ultra-fine TiCN powders were effectively prepared by ball milling. With the increasing of ball-powders ratio and milling time, the average particle size reduces first and then rises, and when milled for 50h with ball-powders ratio of 8:1, the ultra fine spheroidal powders of TiCN with the average size of 0.84μm can be obtained.2.Ultra-fine TiCN matrix cermets were prepared by a microwave sintering. With the increasing of sintering temperature, the shrinkage rate, relative density, bending strength and hardness of the cermets all rise first and then reduce. And the ultra-fine TiCN matrix cermets sintered at 1500℃for 30 minutes shows small grains, homogeneous microstructures, and excellent properties with 1547MPa of bending strength and 90.6HRA of hardness, which are increased 24.0% and 0.7%, respectively, compared with that of the cermets prepared by convention sintering.3.With the increasing of sintering temperature, the shrinkage rate, relative density, bending strength and hardness of the cermets reforced by nano-Al₂O₃ all rise first and then reduce, the maximal value appeared when the temperature is 1500℃, and the suitable microwave technology is 1500℃for 30min. In this experiment, the addition of nano-Al₂O₃ reduces the mechanical properties of ultra-fine cermets which is due to nano- Al₂O₃'s conglobation.4.With the increasing of sintering temperature, the shrinkage rate, relative density, bending strength and hardness of cermets reforced by nano-Si₃N₄ all rise first and then reduce, the maximal value appears when the temperature is 1500℃, and the suitable microwave technology is 1500℃for 30min.5.With the increasing of the addition of nano-Si₃N₄, the bending strength and hardness of the cermets both rise first and then reduce. When the addition of nano-Si₃N₄ is 2.0vol%, the ultra-fine cermets shows excellent properties with 1749MPa of bending strength and 91.8HRA of hardness. Compared with these of the ultra-fine cermets without nanoparticles, a bending strength and hardness are increased 13.1% and 1.3% respectively. The fracture mode of ultra-fine cermets reforced by nano-Si₃N₄ is intercrystalline fracture and a little transcrystalline fracture of large grained hard phase, and the strengthening mechanism is grain refining and dispersion strengthening.