Research On Interface And Strengthening Mechanism Of WC/HEA High Entropy Cemented Carbide

Cemented carbide has excellent properties such as high strength and corrosion resistance,and is widely used in machining,metallurgy,oil drilling,and mining tools.However,with the continuous improvement of the performance requirements of parts,the mechanical properties of alloys are also constantly improved,and the traditional cemented carbide can no longer meet the actual use requirements.High-entropy alloy has the advantages of high hardness,high strength,and wear resistance,and is suitable for preparing high-performance high-entropy cemented carbide as a bonding phase.However,the interfacial bonding properties of high entropy alloy and hard phase as bonding phase have not been studied,and the mechanism affecting the interfacial bonding properties is still unclear.Therefore,the influence of different kinds of high-entropy alloys on the interface bonding properties of high-entropy cemented carbide was studied by CASTEP software based on the first principles.The high-entropy alloy component with the best wettability with the hard phase is selected by calculation,and the high-entropy hard alloy is prepared by mechanical alloy and gas pressure sintering preparation process,and then additives are used to further to improve the mechanical properties of the alloy.The interface bonding properties of high entropy alloy models on CoCrFeNi,Al Co Cr Fe Ni,Co Cr Fe Ni Mo,and Co Cr Fe Ni Mn with WC were studied by the first-principles simulation method.According to the calculation results,the high entropy alloy material with the best wettability with WC hard phase is selected.According to the calculation of interface binding energy,Co Cr Fe Ni Mn is the high entropy alloy material with the best wettability with WC among the above materials.By observing the electronic structure of the interface model of WC/HEA high entropy cemented carbide,it can be known that Mn atoms have stronger bonding with W atoms than Al atoms and Mo atoms at the interface,so the interface bonding energy between Co Cr Fe Ni Mn and WC is the highest.According to the density of states analysis,the"d"electron orbital of atoms is the main reason for the strong bond between atoms.WC/HEA（CoCrFeNi,AlCoCrFeNi,CoCrFeNiMo,and CoCrFeNiMn）high entropy cemented carbide samples were prepared by mechanical alloy and gas pressure sintering method.By testing its mechanical properties,it is known that the mechanical properties of WC/Co Cr Fe Ni high entropy cemented carbide are improved after adding the solute element Mn.However,the mechanical properties of WC/Al Co Cr Fe Ni and WC/Co Cr Fe Ni Mo high entropy cemented carbides with solute elements Al and Mo decreased.It is found that the mechanical properties of WC/HEA high-entropy cemented carbide are the best when Co Cr Fe Ni Mn high-entropy alloy is selected as the bonding phase,and its Vickers hardness,fracture toughness,and bending strength are 1562HV₃₀,9.3MPa m^1/2 and 850MPa.WC/CoCrFeNiMn high entropy cemented carbide was prepared by mechanical alloy and gas pressure sintering method of Fe and Y₂O₃ as additives.It is found that the optimum addition of Fe is 0.5wt.%,and the Vickers hardness,fracture toughness,and bending strength of WC/Co Cr Fe Ni Mn high entropy cemented carbide is 1614HV₃₀,10.6MPa·M^1/2 and 1330MPa.The optimal addition of Y₂O₃ is 0.7wt.%,and the Vickers hardness,fracture toughness,and bending strength of WC/Co Cr Fe Ni Mn high entropy cemented carbide is 1634HV₃₀,11.1MPa·m^1/2 and 1130MPa.When the optimum amount of the two additives is added at the same time（0.5wt.%Fe+0.7wt.%Y₂O₃）,the properties of WC/Co Cr Fe Ni Mn high-entropy cemented carbide are the best,and its Vickers hardness,fracture toughness,and bending strength is 1618HV₃₀,11.6MPa·m^1/2 and1450MPa.Compared with WC/Co Cr Fe Ni Mn high entropy cemented carbide without additives,its Vickers hardness,fracture toughness,and bending strength is improved by4%,25%,and 70%.It is found that the strengthening mechanism of these two additives includes interfacial strengthening of the bonding phase and fine-grain strengthening of the hard phase.Through the research in this thesis,it is found that the bonding strength of atoms at the interface is the main factor affecting the interface bonding performance of high-entropy cemented carbide.The calculation results and experimental verification also prove that the interface bonding performance between Co Cr Fe Ni Mn high-entropy alloy and WC is the best.The use of additives can improve the mechanical properties of high entropy cemented carbide,and the metal additive Fe can improve the interface bonding performance and bending strength.Rare earth additive Y₂O₃ can inhibit the growth of WC grains and improve fracture toughness.The prepared high entropy cemented carbide has theoretical guidance and practical reference value for material selection and performance strengthening.The prepared high entropy cemented carbide has excellent mechanical properties such as high hardness and high strength.So it has potential application values in many fields.