Study On Preparation Process And Mechanical Propertises Of Whisker Toughrning TiB₂ Based Ceramic Cutting Tool

Ceramic cutting tool improves the cutting efficiency greatly,even considered to be the best tool of raising the productivity of machining in the world.With the features of high melting point,high conductivity and high elastic modulus,TiB₂ ceramic cutting tool have been caught the attention of scholars both at home and abroad,however,with the own weakness of low brittleness of TiB₂ base ceramic cutting tool materials.Aiming the characteristics of the fracture low of toughness and the basic thoughts of whisker toughening,according to the whisker matrix matching principle,choose appropriate whiskers can improve the comprehensive performance of TiB₂ tools.The main content of the project are:carbon thermal reduction method to synthesize TiC whisker and its growth mechanism is analyzed,whisker dispersed treatment,sintering and mechanical properties in combination with microscopic structure optimization analysis.Researching the TiC whisker synthesis of VLS,VS growth mechanism,and the mechanism of SLLS in-depth investigation.SLLS mechanism have a good explanation of NaCl convey raw materials to Ni,achieve the change of the S-L,With system goes constantly,whisker has realized the nucleation process of grow up.SLLS mechanism as well as the VLS mechanism need Ni melt drop guide whisker growth,so Ni melt drops of the top of the whisker can not as the only standard to judge the VLS mechanism.Basing on the characteristics of synthetic TiC whisker easy reunion after,the basic principle of particle dispersion and the wetting Angle,dispersant,dispersed medium is studied.Analyzing particle dispersion methods,the using of combining physical dispersing method and chemical method.Our experiment selected sodium silicate and polyethylene glycol 6000 as dispersing agent,and the matching of the dispersion medium for distilled water and anhydrous ethanol,Consideration the sodium silicate dispersing process may remain and the volatile properties of polyethylene glycol?peg?6000,eventually we choose polyethylene glycol?peg?6000 as TiC whisker of dispersant.Study optimizing of sintering temperature range 1650¹750?of the TiC whisker toughening TiB₂ composite powder of ceramic cutting tool,TiCw/TiC particles toughening TiB2 base ceramic cutting tool materials were made.TiC whisker content and sintering process is studied on the mechanical behavior and microstructure of composite ceramic cutting tool.Researchs show that the performance of mechanics,as TiC whisker/particle concentration increases,bending strength,fracture toughness and hardness of the material increase gradually,when the TiC whisker/particle composite powder reach the content of 30vol%,comprehensive mechanical performance of ceramic cutting tool is best,when the TiC whisker/particle composite powder content is more than 30 vol%,bending strength,fracture toughness and hardness of ceramic cutting tool will be lower.Studing the TiB2 30%TiC whisker/grain ceramic cutting tool materials in the sintering process and microstructure,research has shown that the sintering temperature and holding time at 1700?,and 30 min respectively,Composite ceramic cutting tool materials of small grains,bending strength and fracture toughness are better.