Study on the Preparation of WC-Co Coarse-Grained Cemented Carbide by Chemical Co-Precipitation Method and Its Microstructure and Properties AITranslate

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Chinese Library Classification Number:TG135.5[一般工业技术]

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To achieve the uniform dispersion of the hard phase and the metallic binder of cemented car-bides,Co nanoparticles were uniformly coated on the surface of WC particles by the method of chemical co-precipitation followed by hydrogen reduction using CoCl₂·6H₂O and(NH₄)₂C₂O₄·H₂O as raw materi-als.The effects of chemical co-precipitation process parameters on the precipitation rate and the distribu-tion uniformity of WC-CoC₂O₄·2H₂O precursor powder were studied.WC-Co composite powders with different Co contents were pressed and sintered into cemented carbides.The effects of preparation methods of WC-Co composite powders(chemical co-precipitation-hydrogen reduction vs.manual mixing)and Co content on the metallographic microstructure and mechanical properties of cemented carbides were studied.The results show that the optimized process parameters of chemical co-precipitation are as follows:reac-tion time of 1 h,reaction temperature of 50℃,precipitant addition time of 5 min,CoCl₂solution concentra-tion of 0.038~0.15 mol/L,precipitant excess ratio of 1.8,and pH value of 6.When the Co content is≤2%,the cemented carbide prepared by chemical co-precipitation exhibits significantly reduced pores and defects in its microstructure compared to manually mixed samples,along with enhanced flexural strength and impact toughness.However,when the Co content reaches 14%,the pores and defects of the cemented carbide prepared by chemical co-precipitation increase significantly,and its flexural strength and impact toughness decrease significantly.Within the 6%~14%Co content range,the cemented carbides prepared by chemical co-precipitation demonstrates larger average WC grain sizes and higher overall relative densi-ties compared to manually mixed samples,while maintaining comparable hardness values.With the increase of Co content,the average grain size of WC in cemented carbides increases,and both the relative density and hardness show an overall decreasing trend.The WC-Co coarse-grained cemented carbide prepared by che-mical co-precipitation exhibits excellent mechanical properties.At 12%Co content,the cemented carbide achieves an average WC grain size of 4.2μm,a relative density of 99.6%,a Rockwell hardness of 86.3 HRA,a flexural strength of 2185 MPa and an impact toughness of 31 kJ/m².