Preparation Technology And Microstructure Of Normal Nanometer WC-5TiC-10Co Cemented Carbide

Traditional WC-Co cemented carbide has special properties,such as good wearing resistance property and hardness.It is used in cutting tool,mold and mining wildly.The wearing resistance property and hardness of WC-TiC-Co cemented carbide is higher than traditional WC-Co cemented carbide,the reason is that hardness of TiC is higher than WC.Because of(TiW)C solid solution,softening rate of WC-TiC-Co cemented carbide is low at high temperature.The aim of this study is to manufacture normal nanometer WC-TiC-Co cemented carbide to get over fragility, machining softening,low toughness.This paper has manufactured normal nanometer WC-5TiC-10Co powder by a planet type ball milling technique.The materials are micrometer WC,TiC and Co that original average particle is 2.26μm.The pressing block pressed with different mode were sintered with different sintering technics,and the relation between sintering temperature,pressing mode and density,shrinkage rate,hardness, transverse rapture and pressure strength,and researched the microstructure Through(1)Normal nanometer WC-TiC-10Co composite powders were manufactured by ball-mill in the ethanol with 220r/min rotation,and the ratio of balls and powders is10 to 1.The ratio of average particle at milling-time less than 60 hours is slowly 2.26μm to 0.51μm,and the particle uniformly distributing present grainy or strip.(2)Rate of pressing have no effect on the pressing-block density.The keeping-time is 2min,not oily efficiency is high,but also the pressing-block density is high.(3)The temperature increased from room temperature to 600℃at speed of 10℃/min,and keeped 30min.Then the temperature increased to 1200℃at speed of 5℃/min ande keeped 30min.Finally,the temperature increased to sintering temperature(1300℃,1350℃and 1400℃)at speed of 5℃/min and keeped the temperature 1h.(4)With sintering temperature increasing,the density of sintering-block is increasing.When the sintering temperature is among 1300～1400℃for normal nanocrystalline WC-TiC-10Co cemented carbide,the pressing blocks of pressing pressure 50MPa(80MPa,100MPa and 150MPa),the density increased from 12.98 g/cm³(13.27 g/cm³,13.56 g/cm³,13.81 g/cm³)to 13.80g/cm³(14.09g/cm³,14.41 g/cm³,14.27 g/cm³).(5)With sintering temperature increasing,the shrinkage rate of sintering-block is increasing.When the sintering temperature is among 1300～1400℃for normal nanocrystalline WC-TiC-10Co cemented carbide,the pressing blocks of pressing pressure 50MPa(80MPa,100MPa and 150MPa),the shrinkage rate S increased from 20.67%(21.09%,21.88%,22.34%)to 21.11%(21.56%,22.00%,23.33%).At the same sintering temperature,the shrinkage rate of sintering-block descended with pressing pressure increased.(6)At the same pressing pressure,the density of normal nanometer WC-TiC-10Co cemented carbide increased with sintering temperature increasing. When the pressing pressure is 100MPa,the hardness is highest,91.1HRA at sintering temperature 1350℃.The hardness at sintering temperature 1400℃is 91.2HRA.(7)With the sintering temperature increased,the pressure strength of the pressing blocks of pressing pressure 100 MPa augmented,the highest date is 1589MPa at 1400℃.With the sintering temperature increased,the tensile strength of the pressing blocks of pressing pressure 100 MPa augmented,the highest date is 896MPa at 1400℃.(8)To research the unerode sintering block,we found that there were some pore and impurity.They effect the continuity and integrity of the materials,and make mechanical properties of material descending.(9)With the sintering temperature increased,porosity descended.It shows that the densification of sintering blocks enhanced with temperature increasing.(10)The structure for normal nanocrystalline WC-TiC-10Co cemented carbide by optical microscope are(TiW)C+WC+γ+ηphase.The strength of nanocrystalline WC-TiC-10Co cemented carbide decline due to theη₁ phase,theη₁ phase avoid in the sinter.Crystal unconventionality grow up in the sinter bring on the strength declining,the essential technical measure were adopted for fine crystal.(11)At the sintering temperature of 1350℃,crystalline grain of WC and(Ti,W)C in WC-TiC-10Co cemented carbide is thin.When the temperature increased to 1400℃,the grain size growth obviously.(12)Seen from macro view,the break furface of normal nanocrystalline WC-TiC-10Co cemented carbide looks flat and brightess,belongs to brittleness rupture,and the mode of rupture is along crystal rupture.SEM photographs of normal nanocrystalline WC-TiC-10Co cemented carbide bending resistance specimen has apparent model nest,which shows that the sample occurs definite madel distortion.