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n this paper, a type of Si3N4/TiC micro-nanocomposite ceramic tool materials were fabricated via hot pressing technique by adding Si3N4 and TiC nanoparticles. Cutting forces, temperature and wear behavior in dry machining of nodular cast iron with Si3N4/TiC micro-nanocomposite ceramic tool were investigated, in comparison with a commercial Sialon ceramic tool. Turning experiments were carried out at three different cutting speeds, which were 110, 175, and 220 m/min. Feed rate ( f ) and depth of cut (ap) were kept fixed at 0.1 mm/rev and 0.5 mm. The results show that the radial thrust force (Fy) become the largest among the three cutting force components (Fx , Fy and Fz), and Fy is the most sensitive to the changes of feed rate and depth of cut. In dry cutting of nodular cast iron, the cutting tool temperature rise rapidly with increase in cutting speed. The cutting temperature reach nearly 1000°C at the cutting speed of 220 m/min. The two types of ceramic tools have similar cutting performance, while the Si3N4/TiC micro-nanocomposite tool exhibits a better cutting performance than that of the Sialon tool. The wear rate of Si3N4/TiC micro-nanocomposite ceramic cutting tool is mainly dominated by the abrasion, while the wear rate of Sialon ceramic cutting tool is dominated by the abrasive action, and pullout of grains.

Al2O3-TiC-ZrO2 micro-nano-composites with addition of ZrO2 nanoparticles were fabricated by vaccum hot pressing with Mo and Ni powders as sintering aids. Results showed that the mechanical properties and relative density of the micro-nano-composites increased firstly and then decreased with the increase in the content of ZrO2 nanoparticles. Al2O3-TiC-ZrO2 micro-nano-composites containing about 4vol% ZrO2 nanoparticles have the highest synthetical properties, its flexural strength, Vicker's hardness, Fracture Toughness and relative density are 920MPa, 20.4GPa, 6.3MPa•m1/2 and 98.9%, respectively. The microstructural characterization revealed that adding proper ZrO2 nanoparticles to the matrix can greatly strengthen the grain boundaries, causing more transgranular fractures and consuming more fracture energy. The excessive amount of ZrO2 nanoparticles may bring about agglomeration effect, leading to the decrease of properties of the micro-nano-composites.

Al2O3-TiC-ZrO2 ceramic composites (ATZ) were fabricated by hot-pressed sintering. The phases and microstructure of the composites were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative density and mechanical properties (flexural strength, fracture toughness and Vicker’s hardness) of the composites were tested. The results show that the microstructure of the composites was the gray core-white rim. With the increase of sintering temperature, the relative density and mechanical properties of the composites increased first and then decreased. The composite sintered at 1705℃ has the highest synthetical properties, and its relative density, flexural strength, fracture toughness and Vickers hardness are 98.3%,970MPa,6.0 MPa•m1/2 and 20.5GPa, respectively.

Si3N4-based composite ceramic tool materials reinforced with TiC0.5N0.5 particles were fabricated by using hot-press-sintering technique with Al2O3 and Y2O3 as sintering aids. The effects of the content of TiC0.5N0.5 on the microstructure and properties of composite ceramic were investigated. The experimental results show that optimal mechanical properties were achieved for the composite with the addition of 20 vol.% TiC0.5N0.5 microparticles, with the flexural strength, fracture toughness and Vicker's hardness being 838 MPa, 8.5 MPa•m1/2 and 15.6 GPa. The fracture surface microstructure of the composites is characterized by scanning electron microscopy (SEM). Phase identification was carried out by X-ray diffraction (XRD). It was found that the microstructure of the material was homogenous and the elongated grain of β-Si3N4 was interlaced. And the fracture surfaces were observed to exhibit a mix of intergranular and transgranular fracture.