Preparation And Properties Of WC-8Co Cemented Carbide Synergistically Strengthened With Graphene And Alumin

WC-Co carbide was widely used in machining,mining and other industrial fields due to its high hardness,high wear resistance and good toughness.The development of modern industry puts forward higher requirements for the performance of traditional WC-Co alloy.Therefore,with the goal of improving the hardness,fracture toughness and wear resistance of the alloy at the same time,graphene oxide（GO）adsorbed alumina（Al₂O₃）was used as the composite reinforcement phase,and WC-8Co-RGO/Al₂O₃ composites with different RGO/Al₂O₃ contents were obtained by hot pressing and sintering,and the strengthening mechanism was explored from the aspects of powder morphology,grain size,microstructure,density and indentation crack propagation.The results are as follows:（1）The enhanced phase exists at the interface in the form of RGO/Al₂O₃adsorption structure and separate Al₂O₃ particles,which hinders the dissolution and precipitation of WC grains and grain boundary migration,thereby refining the grains and improving the uniformity of the tissue.（2）The enhanced phase makes the powder reach the liquid phase state faster,promotes the diffusion of the liquid phase and the flow and discharge of the gas,so that the Co phase uniformly fills the WC grain gap and improves the density.（3）The mechanical properties of the specimen first increased and then decreased with the increase of RGO/Al₂O₃ addition,and were best at 0.1wt%content,with a hardness of 1840.4 HV₃₀ and a fracture toughness of 11.3 MPa·m^1/2.Combined with the Lee-Gurland hardness model,the theoretical hardness of the sample is calculated and compared with the measured value,and the results show that grain refinement is the main reason for the hardness increase.However,when the indentation crack propagation,due to the hindrance of RGO/Al₂O₃ and the mismatch between the thermal expansion coefficient of Al₂O₃ particles and the matrix WC,the residual stress is formed in the micro-area,which makes the crack deflection and bridging,consumes the crack propagation energy and improves the fracture toughness of the sample.（4）During the friction process,RGO/Al₂O₃ is attached to the wear surface and combined with abrasive chips to form a friction layer with better mechanical properties to strengthen the protection of the matrix.The specimen containing RGO/Al₂O₃ is relieved by the plastic deformation of WC grain to alleviate the stress concentration,avoid surface cracking and microcrack propagation,and improve the wear resistance of the specimen.In addition,RGO/Al₂O₃ improves the thermal conductivity of the specimen and reduces the degree of oxidation wear on the worn surface.Therefore,specimens with RGO/Al₂O₃ added have better wear resistance.