Papers by Keyword: Ti(C,N)

Abstract: The fracture toughness and hardness of Ti (C_0.7N_0.3)-19Mo₂C-xNbC-24Ni cermets (x = 0, 5, 20) were studied. Fracture toughness of 5 NbC was the largest, and it of 20 NbC was the lowest. The microstructures of all the cermets consisted of Ti (C,N) and solid soluted Ti (C,N) hard phase, and Ni binder phase. The solid soluted Ti (C,N) surrounded Ti (C,N), namely, core-rim structures were observed in 0NbC and 5NbC. On the other hand, the isolated Ti (C,N) and solid soluted Ti (C,N) were observed in 20NbC, as a result of the phase separation between Ti (C,N) core and solid soluted Ti (C,N).

Abstract: The present review will try to sum up the research on the microstructure and properties of the Ti(C,N)-based cermets materials in recent years. Firstly, the development history, the microstructure and mechanical properties of Ti(C,N)-based cermets, and the relationship between Ti(C,N)-based cermets microstructure and their properties were introduced respectively. Secondly, Compared with different microstructure and properties of Ti(C,N)-based cermets material which were made by different composite constituent. Furthermore, the relationship between mechanical properties of Ti(C,N)-based cermets and sintering method was introduced. Results show that the high performance products can be produced by means of fast sintering techniques at low temperature successfully, such as spark plasma sintering technology. However, the most widely used way is vacuum sintering method. Lastly, the development trend of Ti(C,N)-based cermets were included.

Abstract: Ti(C,N)-based cermets were fabricated by the vacuum hot-processing technique. The effect of sintering process, initial powder size and binder content on mechanical properties of Ti(C,N)-based cermets were investigated. The composite was analyzed by the observation of scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). The results showed that a lower sintering temperature led to insufficient liquid-phase sintering process, which reduced the density of the composite. However, higher temperature and longer holding time resulted in abnormal grain growth, which was not good for improving the mechanical properties of the composite. With the refinement of the initial powder size of the Ti(C,N), the fracture toughness reduced slightly, the flexural strength and Vickers hardness increased. The better mechanical properties were obtained when the binder content of the cermets was designed based on the eutectic composition of Mo-Ni binary alloy phase diagram.

Abstract: β-Sialon/Ti(C,N) composites were prepared using low and middle grade bauxite and ilmenite as raw material,while coke as reducing agent in high purity nitrogen atmosphere through carbothermal reducrion-nitridation(CRN).The main phases of low and middle grade bauxite are kaolinire(Al2O3•2SiO2•2H2O) and (Al2O3•H2O)2 and ilmenite mainly contain ilmenite(FeTiO3) and rutile(TiO2).The reaction products of bauxite are the β-Sialon(Z=3,Si3Al3O3N5) while those of ilmenite are TiC and Fe.The results showed that the main phases are β-Sialon,Ti(C,N),Al2O3 and Fe when the reaction temperature is at 1400°C holding for 4 hours(10wt% ilmenite and 90wt% bauxite as raw material).However,β-Sialon decomposes into 21R at 1450°C and into 15R and AlN at 1500°C.So 1400°C is selected as the proper temperature to synthesize β-Sialon/Ti(C,N) composites.At 1400°C,the β-Sialon crystals with the largest quantity grow well and show long column in shape.With the increase of the reacrion temperature β-Sialon begin to decompose,the β-Sialon crystals change to short columnar,with the number decreasing quickly.

Abstract: Ti(C,N) powder was prepared via carbothermal reduction nitridation (CRN) using rutile and carbon black as the raw material. The phase evolution and the reaction mechanism during the CRN synthesis of Ti(C,N) were investigated, and the effect of reaction temperature and C/TiO₂ molar ratio on the phase composition and x value in TiC_1–xN_x was analyzed. The XRD and SEM results show that: Ti(C,N) powder was synthesized at 1500°C for 4h with the C/TiO₂ molar ratio of 2.2, under the nitrogen pressure of 0.2MPa. Irregular granular structure and the growth stripes were observed in the final products. The growth of Ti(C,N) grains in CRN process was followed by the gas-solid mechanism.The phase compositions of the products were quite dependent on the reaction temperature and the C/TiO₂ molar ratio. The TiN content in Ti(C,N) decreased with the increase of reaction temperature. TiC_1–xN_x powder with different x values can be synthesized by optimizing the experiment conditions including the synthesis temperature and the C/TiO₂ molar ratio.

Abstract: TiB2-Ti(C, N)-(Ni, Mo) composite ceramic tool materials were fabricated by the hot-press sintering technology. The effects of the content of Ti(C, N) on the microstructure and mechanical properties were investigated by XRD and SEM observations. It is shown that the grain size of the composites is small, the fracture surface is irregularity, the grain boundaries of TiB2 and Ti(C, N) are connected tightly, and a new crystalline phase of MoNi is formed. A small amount of Ti(C, N) is decomposed into TiN, and the decomposition of Ti(C, N) is intensified as the content of Ti(C, N) is increased during the sintering process. The fracture pattern is the combination of the intergranular mode and transgranular mode. It is found that the flexural strength and fracture toughness of TiB2-Ti(C, N)-(Ni, Mo) composites increase consistently owning to the addition of Ti(C, N), the maximum resultant mechanical properties of TiB2-Ti(C, N)-(Ni, Mo) composites are 1019.53MPa for the flexural strength, 6.89MPa•m1/2 for the fracture toughness and 23.65GPa for Vickers hardness.

Abstract: Cermets Ti(C，N)_80%Co_(10-x)% TiC_10% Cu_x%(wt%，x=0，1，2，3， 4， 5) were prepared by powder metallurgy method under vacuum condition at 1500°C and the effects of Cu element to the electrical resistivity and flexural strength were studied in this paper. It turns out the electrical resistivity of the samples obviously decreases with the introduction of Cu element, but the electrical resistivity of the samples increases when the amount of Cu element in the samples becomes more. The flexural strengths of the samples decrease with the amount of Cu element increasing. Ti（C，N）_80% Co_9%TiC_10% Cu_1% shows the lowest electrical resistivity and the biggest flexural strength, 7.35*10-7Ω•m and 50.6Mpa. This may be due to the big wetting angle between Cu and the powders of the based body. With the amount of Cu element increasing, the obvious interfaces are made thus the electrical resistivity becomes bigger.

Abstract: Ti(C,N)/Al₂O₃ in situ solid solution composites have been synthesized by mechanically induced self-propagating reactive synthesis (MSR) from the mixture of Ti, Al, C and TiO₂ in nitrogen milling atmosphere. The phase transformation and powder morphology characteristics were studied by using XRD and SEM. Full dense and pure Ti(C,N)/Al₂O₃ composites were fabricated at 1450 °C for 1 h under 10 MPa. The phase composition, microstructure and some mechanical properties of the composites were investigated. The results show that the synthesized Ti(C,N)/Al₂O₃ composites posses a density of 4.66 g/cm³ and a good combination of mechanical properties of hardness of 25.54 GPa and the flexural strength of 404 MPa. The reaction process mechanism was also discussed.

Abstract: Si₃N₄-Ti(C,N) nanocomposites fabricated by vacuum hot pressing with Al₂O₃ and Y₂O₃ as additives were investigated. The results showed that the α-Si₃N₄ phase converted completely into whisker-shaped β-Si₃N₄ grains after vacuum sintering at 1700°C. Suitable addition and well dispersion of the Ti(C,N) particles can restrained the lateral growth of the β-Si₃N₄ grains, increasing aspect ratio of the β-Si₃N₄ grains and improving bending strength of the composites. Fracture toughness of the composites is higher than that of the β-Si₃N₄ ceramics, and the main toughening mechanism is crack bridging due to the higher aspect ratio of the β-Si₃N₄ grains.With the addition of 1vol% of Ti(C,N), the composite has a relative density of 99.31%, Vicker’s hardness of 15.9 GPa, bending strength of 993 MPa, and fracture toughness of 9.9 MPa·m^1/2.

Abstract: Al₂O₃-Ti(C,N)composite ceramics were prepared by in situ aluminothermic reduction and pressureless sintering. The effects of different Ti(C,N) contents and sintering temperatures on microstructure and mechanical properties (bulk density ,apparent porosity and blending strength)of samples were investigated through experiments.The results show that Al₂O₃-Ti(C,N) composite ceramics with 10 wt.% Ti(C,N) prepared using titanium dioxide and metal aluminum powder as raw materials and sintered at 1300 °C for 3h under a flowing nitrigen stream have good properties ,with bulk density 2.94g/cm³,apparent porosity 26.4%, and blending strength reaches to 28.04 MPa. According to the microstructure analysis,the fine in situ synthesis Ti(C,N) particles are uniformly dispersed in tabular alundum matrix. Ti(C,N) and tabular alundum phases are closely combined and can inhibit grain growth each other,which is benefical in improving the comprehensive properties of composite ceramics.