Preparation Of Solid-Liquid Doped WC-Co Cemented Carbide And Study On Its Microstructure And Mechanical Properties

Cemented carbide is a composite material prepared by powder metallurgy technology,which has excellent properties such as high hardness and wear resistance,and is called"industrial teeth".WC-Co cemented carbide is one of the most widely used cemented carbides at present.Because of its excellent comprehensive properties,it is used in excavation,cutting,machining and other industrial fields.However,with the rapid development of industry,traditional cemented carbides are gradually unable to meet people’s technological manufacturing requirements.People optimize the composition,microstructure and preparation process of cemented carbide to improve its comprehensive performance.A large number of studies have shown that the performance of cemented carbide will be improved with additives.Therefore,this thesis prepares Y₂O₃,ZrO₂and Mo-doped WC-Co cemented carbide through a new type of solid-liquid doping and SPS process,and studies the effects of additives on the structure and mechanical properties of cemented carbide.The composition,microstructure,density,hardness and fracture toughness of WC-Co-based cemented carbide were analyzed by XRD,SEM,TEM.The main research results are as follows:（1）WC-Co-Y₂O₃cemented carbide was successfully prepared by solid-liquid doping and SPS process at 1150 ℃ and 50 MPa pressure.Through the solid-liquid doping process,Y₂O₃can be added to the WC-Co alloy powder more uniformly.Compared with the WC-Co sample without Y₂O₃,the density and WC grain size of the alloy sample with a Y₂O₃content of 1.3 wt.%did not change much;the Vickers hardness and fracture toughness were 1446.9 HV and 11.9 MPa·m^1/2,the fracture toughness is increased by 9.2%on the basis of keeping the hardness unchanged.TEM results show that the Y₂O₃phase and the WC phase have a semi-coherent structure,which enhances the interphase bonding force and fracture toughness.（2）WC-Co-Y₂（Zr）O₃cemented carbide was obtained by solid-liquid doping and SPS process at 1250 ℃ and 50 MPa pressure,and effects of Y₂（Zr）O₃on the microstructure and mechanical properties of WC-Co cemented carbide was studied.The results show that the Vickers hardness and fracture toughness of the alloy sample with a ZrO₂content of 0.15 wt.%are 1428.6 HV and 12.8 MPa·m^1/2,respectively.Compared with the sample with Y₂O₃alone,the fracture toughness is further improved while maintaining high hardness,an increase of 7.6%.TEM results show that Y,Zr and O elements exist in the form of Y₂（Zr）O₃compounds.Compared with the sample with Y₂O₃alone,the interphase bonding force and fracture toughness are further enhanced(the fracture toughness of the Y₂O₃-doped sample is 11.9 MPa·m^1/2).（3）The effect of Mo on the microstructure and mechanical properties of WC-Co cemented carbide was studied.The results show that Y₂O₃and Mo can be added to the WC-Co alloy powder more uniformly through the solid-liquid doping process.The WC grain size of the alloy sample with a Mo content of 3 wt.%has a certain decrease;the Vickers hardness and fracture toughness are 1584.1 HV and 11.8 MPa·m^1/2,respectively.Compared with the sample with Y₂O₃alone,the fracture toughness is maintained on high level,the hardness has been improved.TEM results show that the combined effect of the Co phase and the Mo phase inhibits the diffusion of W atoms in the binder,reducing the grain size to a certain extent,and increasing the hardness;at the same time,the presence of Mo atoms in the Co phase improves the phase internal strength of the cemented carbide,leading to an increase in the hardness of the WC-Co-Y₂O₃-Mo cemented carbide.