Research On Sintering Technology Of Nanostructured WC-10Co Hardmetal

Ultra-fine or nanostructured WC-Co hardmetals with superior hardness, superior toughness, superior strength to wear and fatigure strength can meet the challenge of fine edge, high resistance to wear,high shock resistance of machining tools in precision or ultra-precision finishing of numerical control machine. Until now, many methods have been applied in the preparation of nanosized WC-Co powder, but it is many problem to solve to get nanostructured WC-Co hardmetals in sintering. In this work, the experiment have been done to research the sintering of nanosized WC-Co powder prepared with high energy ball milling through the vacuum sintering. It is great significance in theory and technology to study and develop the nanonstructured cemented carbide tools in precision or ultra-precision finishing.Firstly, the experiment to investigate the decarbonizion of nanostructured WC-10Co powder prepared with high energy ball milling during vacuum sintering. Severe decarbonization is happened in nanostructured WC-lOCo when sintering in vacuum.The main phase formed after decarbonization are C03W9C4, C03W3C, W2C and W through the X-Ray Diffraction(XRD). The experiment use cut and try to add free carbide to remove the decarbonization phase. It is found that the best content of free carbide is 2.4wt.% to remove the total decarbonization ,an get the cemented carbide with finest microstructure and highest densification. The reason of severe decarbonization are the oxygen absorbed in nanostructured WC-Co powder in high energy ball milling and the high density of defects in the nanostractured WC-Co powder.The vacuum sintering mechanism of nanostructured WC-Co powder prepared withhigh energy ball milling was investigated through experimental research. This implies that the process of sintering densification of nanosized WC-Co powder was completed in the initial 30 minutes. Compared with the conventional WC-Co cemental carbide, it was found that the nanostructured WC-Co cemental carbide have higher hardness, higher toughness and has finer microslructure.The dependence of microslructure and mechanical property on the technical parameter of vacuum sintering was also investigated in this paper; the density, hardness,fracture toughness KIC and microstructure of the sintered nanostructured WC-Co cemenlal carbide was measured and analysed to have determined the optimal sintering parameter. It conclude that the pressure intensity of sample is 80MPa, the sintering temperature is 1380C, the sintering lime is 60 minutes was the optimal parameters of vacuum sintering.In addition, the sintering of nanosized WC-Co cemental carbide with grain growth inhibitor was investigated. This implies that the single grain growth inhibitor VC, Cr3C2 or CeO2 can inhibite the WC grain coarsening, the result also show that it can pot increase the hardness and toughness of hardmelals. Further investigation on the sintered nanosized WC-Co cemented carbide wth VC, Cr3C2 and CeO2 in the same time, and the result show that the nanostructured WC-10Co cemental carbide has the finest microstructure and highest hardness when doping with 1.5wt.%VC+1.5wt.%Cr3C2 +0.2.wt.%CeO2.