Research On The Preparation Of TiVC2 And TiVC2 Composites

The synthesis of titanium vanadium carbide by carbothermal reduction of partial ammonium vanadate,graphite and titanium powders was systematically studied by means of regression orthogonal experiments combined with thermodynamic analysis,X-ray diffraction,SEM and TG-DSC.The influence of reaction temperature,holding time,ration of partial ammonium vanadate and titanium,carbon contents on products were discussed in detail by regression orthogonal equation obtained.The optimal process parameters for titanium vanadium carbide preparation were stabilited in the laboratory.Finally,new types of TiVC2 cemented carbides were fabricated.The thermodynamic analysis shows that series of intermediate vanadium oxide were formed first with temperature increasing and then TiVC2 appeared at higher temperatures when TiV and TiC formed.Combined thermal analysis shows that whole reaction of partial ammonium vanadate,graphite,titanium powders and fractional order reaction of partial ammonium vanadate,graphite were similar..The results of regression orthogonal equation and products phases analysis showed that factors of holding time and carbon contents have great influence on the formation of TiVC2 solid solution.TiVC2 peaks performed well when the reaction temperature was 1700℃,holding time was3.5h,raion of partial ammonium vanadate and titanium was 1.05,carbon content was 1.However,free carbon peaks could be detected.Further optimized experiments indicated that when the carbon content was 0.825,single TiVC2 solid solution was obtained.Finally,TiVC2 cemented carbides were prepared with TiVC2 powders fabricated under the optimal condition and mechanical properties were determined.Results showed that the TiVC2cemented carbide with addition of 8%Co as single binder had best mechanical properties.The impact toughness was 3.7 J/cm~2and hardness was HRA80.When Co and Ni were combined added,the TiVC2 cemented carbide with Co/Ni ration of 6:4 had best mechanical properties.The impact toughness was 3.57 J/cm~2and hardness was HRA90.