Papers by Keyword: Ceramic Tool Material

Abstract: Aiming at the low mechanical property of existing self-lubricating ceramic cutting tool material, a new Al₂O₃ based nanomicro composite gradient self-lubricating ceramic tool material was developed by applying the design concept of nanomicro composite. The self-lubricating ceramics was composed of ceramic matrix and self-lubricating component, and was prepared by hot pressing technology at a hot-pressing temperature of 1650°C, pressure of 30MPa, and duration of 15min. The model of gradient ceramic tool material is symmetrical composition distribution, and the compositional distribution n and layer number are 1.8 and 7, respectively. The result shows that the interfaces between layers are bonded well and no cracks or defects can be observed. Compare with the homogeneous material, the flexural strength, hardness and fracture toughness of Al₂O₃ based graded material increase by 74%, 5.2% and 3.9%, respectively.

Abstract: A new nanomicro composite self-lubricating ceramic tool material was prepared with vacuum hot pressing technique. The effect of nanoAl₂O₃ powders on the microstructure and mechanical properties of nanomicro composite self-lubricating ceramic tool material was investigated. With the increase of nanoAl₂O₃ content, the hardness and fracture toughness first up then down. When the nanoAl₂O₃ content is 4 vol.%, the flexural strength, hardness and fracture toughness reaches 562 MPa, 8.46 MPa·m^1/2 and 18.95 GPa, respectively. The microstructure and mechanical property of nanomicro composite self-lubricating ceramic tool material can be improved by the grain refinement strengthening of nanoAl₂O₃.

Abstract: A 3D finite element polycrystalline microstructure model of ceramic tool materials is presented. Quasi-static crack propagation is modeled using the cohesive finite element method (CFEM) and the microstructure is represented by 3D Voronoi tessellation. The influences of cohesive parameters, the ratios of maximum traction of grain boundary to maximum traction of grain on the crack patterns of Al2O3 have been discussed. This study has demonstrated the capability of modeling 3D crack propagation of ceramic microstructure with CFEM and Voronoi tessellation model. It is found that the fracture mode is changed from intergranular to transgranular as the maximum traction of grain boundary is increased.

Abstract: In the paper, the Voronoi tessellation model is used to represent the microstructure of ceramic tool materials. And a finite element model based on cohesive element method has been developed to investigate the fracture behavior of the microstructure. The influences of mesh densities and cohesive parameters on the cracking patterns have been discussed. It is found that the enhancement of the grain boundary strength is beneficial for raising the fracture resistance of single-phase ceramic tool materials.

Abstract: The relationship between fabrication pressure and microstructure evolution is proposed. A computer simulation coupled with fabrication pressure for the hot-pressing process of single-phase ceramic tool materials has been developed, which uses a two-dimensional hexagon lattice model mapped from the realistic microstructure without considering the presence of pores. The fabrication of single-phase Al2O3 is simulated. The mean grain size of simulated microstructure by Monte Carlo Potts model integrated with fabrication pressure increases with an increase in fabrication pressure, which is consistent with the experiment results. It is shown that Monte Carlo Potts model coupled with fabrication pressure may simulate the microstructure evolution of single-phase ceramic tool materials.

Abstract: The cutting performance and wear mechanisms of whisker-toughening ceramic cutting tools synthesized by carbothermal reduction process have been studied when cutting the hardened alloy steel 40Cr. It is indicated that the wear resistance of ceramic tools is affected by the molar ratio of C and N in tool materials. At low cutting speed, the main tool wear mechanisms are abrasive wear and oxidation wear. At middle and high cutting speed, the tool wear mechanisms are controlled by abrasive wear, adhesive wear, diffusion wear and oxidation wear simultaneously. Adding whiskers to the matrix material is one of the effective means to improve the wear resistance of ceramic cutting tools.

Abstract: Based on the microstructure results of Monte Carlo simulation, a three-dimensional grid model is built up, and imported into the finite element software with C++ language to analyze the mechanical properties of ceramic tool material. The stress field and residual stress of single-phase and multiphase ceramics have been analyzed by the computer simulation technology.

Abstract: A new nano-composite ceramic tool and die material was prepared by vacuum hot pressing technique. The effect of hot pressing technology on the microstructure and mechanical properties of ZrO₂ nano-composite ceramic tool and die material was investigated systemically, and the ceramic tool and die material with good mechanical properties was fabricated successfully. Results show that, the highest flexural strength, fracture toughness and hardness of ZrO₂ nano-composite ceramic tool and die material reaches 1055 MPa, 10.57 MPa∙m1/2 and 13.59 GPa, respectively by means of the vacuum hot pressing technique at 1430 °C for 60min at 35MPa. The flexural strength and fracture toughness has been improved greatly by the optimization of hot pressing technology. In the materials, the optimum sinter process could ensure the t-ZrO₂ stabilized till room temperature that can enhance the toughening effect of ZrO₂. The microstructure of ZrO₂ nano-composite ceramic tool and die materials were improved by the optimization of hot pressing technology, and the fracture mode is the typical mixed trans/inter-granular fracture mode.

Abstract: 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.

Abstract: The fabrication is a key process for the preparation of ceramic tool materials, which governs the mechanical properties of ceramic tool materials under the condition of the same compositions. A computer simulation coupled with fabrication temperature for the hot-pressing process of single-phase ceramic tool materials has been developed using a two-dimensional hexagon lattice model mapped from the realistic microstructure without considering the presence of pores. The fabrication of single-phase Al2O3 is simulated. The mean grain size of simulated microstructure by Monte Carlo Potts model integrated with fabrication temperature increases with an increase in fabrication temperature, which is consistent with the experiment results.