Research On Fine Grained Mould Materials Of Ti(C, N)-based Cermets

Ti(C,N)-based cermets have been high hardness, wear resistance, oxidation resistance, phase stability, low thermal expansion coefficient which are necessary for high temperature processing, and have beem its reasonable toughness and strength.At the beginning of this thesis, the history of Ti(C, N) based cermets, properties and characters, and the main usages were presented, which includes the influence of composition, additive, manufacturing process on the microstructures and properties of Ti(C,N)-based cermets, research achievements on phase reaction and microstructure evolution in sintering process of Ti(C,N)-based cermets. Based on above work, the purpose and significance of the thesis are pointed out. The ultrafine cermet powders and fine grained Ti(C,N)-based cermets have been systematically investigated by powders size analyzer, thermal analysis(DTA), X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM) and (TEM).Starting with the hard phase ultrafine powders and the binder phase micron powders fabricating process by planet ball-milling, we have achieved the ultrafine powders with 0.18~0.21μm median diameter and the regular appearance resembling ball.The influence of particle size of hard phase (TiC, TiN and WC) on sintering process of Ti(C,N)-based cermets has also been investigated. The finer the powders were, the earlier the quick consolidation occurred. Particle size of powders greatly influenced microstructures and properties of cermets. Composition of 30%TiC-10%TiN-12%WC -35%Ni -9%Mo,were used to prepare the sintered body. The sintering temperature are 1420℃,1430℃,1440℃, it is found that 1430℃is the best sintering temperature. Simples sintered at this temperature have the highest TRS and density. Fracture analysis diagram is rock-candy structure, the hard-phase grain and the pores which cause the abruption.