Preparation And Application Of SiC-Whisker-Reinforced Alumina Ceramics By DLP Method

Ceramics are widely used in various industrial fields such as high-speed cutting tools due to their high hardness,stable physical-chemical properties,and excellent wear resistance.The conventional preparation technology of ceramic parts depends on the mold.It is not only a high cost of small batch production,but also challenging to achieve the rapid and free forming of products.Digital light process(DLP)has the advantages of high accuracy,forming efficiency,and densification.It can effectively solve the fabrication problems with small batch ceramic parts and near net-shape.In this thesis,the preparation of SiCw/Al2O3 ceramic slurry,the heat treatment of SiCw/Al2O3 green parts,and the application of SiCw/Al2O3 ceramic cutting tools are investigated.The specific research content of this paper is as follows:Firstly,the composition and preparation process of SiCw/Al2O3 ceramic slurry is proposed.The mechanism of the influence of SiC whiskers on the rheological and curing properties of SiCw/Al2O3 slurry is investigated.The effects of whisker content on the rheological properties and curing behaviors are analyzed by characterizing the viscosity,curing depth and geometrical overgrowth of ceramic slurry.A modified Beer-Lambert model is proposed to evaluate the curing depth as functions of SiCw content and exposure parameters.The mapping relationship between the geometrical overgrowth and curing depth of SiCw/Al2O3 ceramic slurry was established.In addition,the mechanism of the effect of the solid content of Al2O3 ceramic powder and SiCw content on the rheological properties of SiCw/Al2O3 ceramic slurry is described.Secondly,the heat treatment processes of Al2O3 ceramic green part fabricated by DLP method are optimized.Thermogravimetric analysis technology is used to characterize the thermal change process of matter in the ceramic green body.The influence of temperature on the pyrolysis process of organic matter in the green body is analyzed.Then,the optimized debinding scheme of green part is established.The ceramic green parts after debinding are sintering at different sintering temperatures.The effects of sintering temperature of green part on the shrinkage,microstructure and mechanical properties are investigated.The mechanism of the effect of sintering temperature on ceramic fabricated by DLP method is discussed.The heat treatment process during the DLP fabricated process is proposed for alumina-based ceramic by optimizing the debinding and sintering processes.Finally,the SiCw/Al2O3 ceramic cutting tools are prepared based on the optimized composition of ceramic slurry and heat treatment process.The cutting performance of ceramic tools fabricated by DLP method are characterized.The microstructure and mechanical properties of ceramic are characterized,after the SiCw/Al2O3 ceramic prepared by DLP method is sintered with the optimized heat treatment process.The effect of SiCw content on the properties of SiCw/Al2O3 ceramic fabricated by DLP method is analyzed.The cutting performance of SiCw/Al2O3 ceramic tools is investigated by the cutting experiments with the workpiece of the grey cast iron.