| By means of differential scanning calorimeter (DSC), X-ray diffraction (XRD),scanning electron microscope (SEM), transmission electron microscope (TEM), selectedarea electron diffraction (SED), Nitrogen/Oxygen determinator, centrifugal particle analyzer,etc, the preparation of ultrafine grained Ti(C,N)-based cermets and the correlative issueswere systemically investigated in present paper. Research development and movement tendency of Ti(C,N)-based cermets werereviewed, and the effect of grain refinement on microstructure and mechanical propertieswere emphasized in the first part of present paper. The preparation of ultrafine Ti(C,N)-basedcermets was the primary clue throughout this paper. Ultrafine powders of TiC and TiN with uniform particle size distribution weremanufactured by physical process of planetary ball milling, which could satisfy therequirement for this research. Quality of those powders was also compared and evaluated. The pressing characteristics of ultrafine Ti(C,N)-based cermets were investigated. Itwas found that wax could improve the external friction between powders and die walls, thequantity of binder Ni could not cause relative pressed density to increase, however it couldimprove the uniformity of density contribution, and pressing pressure had a great influenceon pressed density, distortion and crack of sintered sample. It was indicated that wax mightbe used as lubricant for ultrafine Ti(C,N)-based cermets shaping. It was found that the rate of heating-up during sintering had a great influence on crackof sintering body, less than 3 ℃ min-1 just adapted to the preparation of ultrafineTi(C,N)-based cermets. The dispersion behavior for ultrafine and nano hard phase powders in water andabsolute ethyl alcohol as well as the effect of surfactants on dispersion were investigated. Interms of the experimental results, the dispersion medium and condition could be reasonablyselected for those powders. The influence of particle sizes of hard phases with coarse, sub-micron and ultrafine sizeon sintering characteristic, microstructure and mechanical properties of Ti(C,N)-basedcermets were systemically investigated. The results distinctly showed the evolutionaryprocess of above aspects. It was revealed that the particle size of raw hard phase had a IIIremarkable effect on rate of shrinkage, density, microstructural homogenity, grain structureand mechanical properties, and ultrafine Ti(C,N)-based cermets were provided with optimaldensification and microstructural homogenity as well as mechanical properties. The deoxygenation of ultrafine Ti(C,N)-based cermets with high oxygen content ingreen compact and solid-state sintering process were studied. The influence of high oxygencontent on microstructure and mechanical properties were almost overcome so that ultrafinestructured Ti(C,N)-based cermets with outstanding mechanical properties were manufactured,for example, the hardness reached the level of HRA93.9, TRS got 2330MPa when N contentin cermets was controlled. The prepared ultrafine structured cermets were of mean grain sizeof about 0.30μm and uniform structure. It was also found that ultrafine Ti(C,N)-basedcermets sintered in vacuum existed serious denitrification. Being analogous to the preparation method of ultrafine Ti(C,N)-based cermets, thesinterability of nano hard phase Ti(C,N)-based cermets were explored. The results openedout that nano hard phase Ti(C,N)-based cermets had very poor sinterability and mechanicalproperties. The effect of chemical compositions of C, N, Mo2C and TaC on microstructure andmechanical properties in ultrafine cermets were investigated. It was revealed that the ratio ofC/N had a significant effect on grain size, higher ratio facilitated grain growth; inverselylower ratio prevented grain from growth. With the extra added C content less than 2.4wt.%,there existed ξ phase in microstructure; in the C content...
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