Research On Strengthening Mechanism And Mechanical Properties Of TiC-CoCrFeNiMn High Entropy Cemented Carbide

Cemented carbide is known as"industrial teeth"because of excellent properties and plays an important role in the field of wear-resistant parts.However,the binder has low hardness and low wear resistance,which limits the application of wear-resistant parts.In recent years,high entropy alloy instead of binder to prepare high entropy cemented carbides to solve the problem.Because of the poor wettability between high entropy alloy and hard phase,the performance of high entropy cemented carbide is lower than traditional cemented carbide.Additives are proposed to improve the comprehensive properties of high entropy cemented carbide.The effects of WC,TaC and Ni on the microstructure,mechanical properties and wear resistance of high entropy cemented carbide were studied,and the strengthening mechanism of the additive on high entropy cemented carbide was revealed.Finally,the type and content of the optimal additive is determined.TiC-CoCrFeNiMn high entropy cemented carbide was prepared by vacuum sintering with WC.Through the mechanical properties test,It is found that the high entropy cemented carbide with 15wt.%WC has the best mechanical properties,which are 2046.4HV₃₀,830MPa and 9.89MPa·m^1/2.Compared with that without WC,which is increased by 41%,26%and 32%.It can be proved from mechanical properties that the addition of WC can improve the properties of cemented carbide.The reason is WC can improve the wettability between high entropy alloy and TiC by forming rim structure,inhibit grain growth.It was found that the fracture form of cemented carbide with WC changed from intergranular fracture to transgranular fracture,which improved the strength and toughness of cemented carbide.The wear experiments show that the high entropy cemented carbide with WC content of 15wt.%has relatively good wear resistance.The wear forms of alloys mainly include abrasive wear,accompanied by oxidative wear and adhesive wear.TiC-CoCrFeNiMn high entropy cemented carbide was prepared by vacuum sintering with TaC.The research shows that when the TaC content is 9wt.%,the mechanical properties of high entropy cemented carbide are 1700.2HV₃₀,750MPa and8.92 MPa·m^1/2,which is increased by 18%,15%and 19%respectively compared with those without TaC.Through SEM and EDS analysis,TaC inhibits grain growth by forming core-rim structure,which plays a role in solution strengthening of the alloy.When the content of TaC exceeds 9wt.%,the agglomeration of TaC will occur,which worsen the properties of cemented carbide.The results of friction and wear experiments show that the high entropy cemented carbide with 9wt.%TaC has the best friction and wear performance,with narrow and shallow wear marks.The main wear forms are abrasive wear,oxidation wear and adhesive wear.TiC-CoCrFeNiMn high entropy cemented carbide was prepared by vacuum sintering with Ni.The experimental results of mechanical properties show that when the Ni content is 3wt.%,the high entropy cemented carbide has the best properties,with Vickers hardness of 1603.9HV₃₀,bending strength of 730MPa and fracture toughness of8.45 MPa·m^1/2,which is increased by 10%,12%and 12%compared with the high entropy cemented carbide without Ni.According to SEM and EDS,the strengthening mechanism of Ni on high entropy cemented carbide is different from WC and TaC,and the rim structure can not be formed.Ni influences the liquid phase sintering process through its good wettability,increases the solubility of liquid phase to TiC hard phase,promotes the dissolution-precipitation process,accelerates the rearrangement and densification of hard phase,and finally strengthens the alloy.The wear experiments show that the wear resistance of high entropy cemented carbide is the best when the addition of Ni is 3wt.%.The main wear forms are abrasive wear,oxidation wear and adhesive wear.The experimental results show that WC is the best additive in improving the microstructure and mechanical properties of high entropy cemented carbide among the three additives.The alloy with WC added has fine and uniform grain size,high hardness,good strength and fracture toughness.The second is TaC,but because of the agglomeration phenomenon of TaC,It is not as good as WC.The last is Ni.The microstructure of the alloy after adding Ni is not significantly improved,and the mechanical properties are improved slightly,far less than WC.This study provides theoretical basis and technical guidance for the preparation of high-performance high-entropy cemented carbide,and has important research value in improving the comprehensive properties of high-entropy cemented carbide.