Research On The Effect Of WC/Al_0.5CoCrFeNiTi_0.5 Binder On The Microstructure,Mechanical Properties,and High Temperature Wear Resistance Of WC Cemented Carbides

WC/Co cemented carbide is widely used in industrial fields due to its high hardness,fracture toughness and wear resistance.However,Co,as a toxic strategic resource,has a high application cost,and WC/Co cemented carbide prepared by Co as binder has poor high temperature softening resistance,resulting in a reduced service life.Therefore,the development of new binders with excellent performance and low cost is a research hotspot in the field of cemented carbide in recent years.High entropy alloys（HEA）possess excellent properties and have good wettability with WC,which provide a good idea to be as the new binder.In this paper,ultrafine grain WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide was prepared by hot pressing sintering process using Al_0.5CoCrFeNiTi_0.5 high-entropy alloy as binder,the effect of process parameters on WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide was analyzed,and the mechanism of Al_0.5CoCrFeNiTi_0.5 binder inhibiting WC grain growth in WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide was discussed.In addition,the friction and wear properties of WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide under high temperature conditions was evaluated,aiming to provide a technical reference for the development of HEA binder with excellent performance and the promotion of WC/HEA cemented carbide for engineering application.In this paper,Al_0.5CoCrFeNiTi_0.5 high-entropy alloy was prepared by mechanical alloying method,and mixed with WC powder by ball milling.The mixed powder is pressed at 10 MPa pressure and then hot-pressed sintered.Ultrafine grain WC was prepared by hot pressing and sintering at 17 wt.%Al_0.5CoCrFeNiTi_0.5,20 wt.%Al_0.5CoCrFeNiTi_0.5 and 25 wt.%Al_0.5CoCrFeNiTi_0.5 binder at sintering pressures of 20MPa,30 MPa,40 MPa and sintering temperatures of 1200°C,1250°C and 1300°C,respectively.Among them,WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide prepared by hot pressing sintering of Al_0.5CoCrFeNiTi_0.5with 20 wt.%binder content at a sintering temperature of 1250°C and a sintering pressure of 30 MPa had the best comprehensive mechanical properties.The density reaches 98.7%,the average grain size of WC is 157nm,and the Vickers hardness and fracture toughness are 2389±5 HV and 15.94±0.2MPa·m^1/2,respectively.Compare WC/10 wt.%Co cemented carbide prepared under the same process parameters,the Vickers hardness and fracture toughness increased by 28.1%and 42.8%respectively.The slow diffusion effect of Al_0.5CoCrFeNiTi_0.5 cemented carbide hinders the diffusion rate of W and C atoms,reduces the"dissolution-precipitation"rate,and inhibits the growth of WC grains.In addition,the Cr₃C₂ phase and complex phase coated on the WC grain increase the WC diffusion path and inhibit the WC grain growth.WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide in addition toγphase,WC phase and M（Co,Fe,Ni）₃W₃C phase,there are also Cr₃C₂ phase and complex ion phase.Al_0.5CoCrFeNiTi_0.5 binder significantly inhibits the growth of WC grains,under the same process conditions,the WC average grain size of WC/20 wt.%Al_0.5CoCrFeNiTi_0.5cemented carbide is reduced by 78.3%compared with WC/10 wt.%Co cemented carbide WC average grain size.This is mainly due to the slow diffusion effect of the Al_0.5CoCrFeNiTi_0.5 binder and the complex phase generated at the interface between WC and Al_0.5CoCrFeNiTi_0.5.WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide in WC grain growth mode is"dissolution-precipitation",the slow diffusion effect of Al_0.5CoCrFeNiTi_0.5 binder hinders the diffusion rate of W and C atoms,reduces the dissolution-precipitation rate,inhibits WC grain growth,and the Cr₃C₂ phase and complex phase coated on the WC grain increase the WC diffusion path and inhibit WC grain growth.Taking WC/Co cemented carbide as a reference,the high-temperature friction and wear properties of WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide prepared under different process parameters at 800°C were studied.The results show that the friction coefficient and wear rate of WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide under all process parameters are lower than that of WC/Co cemented carbide.The WC/Al_0.5CoCrFeNiTi_0.5 cemented carbide prepared by hot pressing sintering at 1250°C and 30 MPa has the lowest wear rate,which is 1.2413×10^-6 mm³/N·m,showing excellent high temperature wear resistance.Al_0.5CoCrFeNiTi_0.5 binder with excellent high temperature oxidation resistance slows down the oxidation rate of WC,improves the high temperature wear resistance of cemented carbide.The wear mechanism of WC/Al0.5Co Cr Fe Ni Ti0.5 cemented carbide at high temperature is mainly oxidation wear,abrasive wear and adhesive wear.