Study On FCC Phase High Entropy Alloy As WC Cemented Carbide Binder

High entropy alloy（HEA）is a kind of solid solution alloy with simple structure,usually composed of five or more elements,which has the characteristics of lattice distortion and slow diffusion that ordinary alloys do not have.Therefore,HEA as a binder is likely to improve the comprehensive properties of WC cemented carbide.In this paper,CoCrFeNiW_x high entropy alloy powder was prepared by mechanical alloying method as binder,and WC cemented carbide was prepared by spark plasma sintering（SPS）.This paper studied the influence of ball milling time on the microstructure of HEA powder,the influence of the composition and content of high entropy alloy binder,holding time and sintering temperature on the microstructure and mechanical properties.This paper also studied the relationship between the composition of CoCrFeNiW_x binder and the friction and wear properties of WC-HEA cemented carbide at high temperature were studied.The results show that:CoCrFeNiW_x high entropy alloy powder with FCC phase and a small amount of BCC phase was obtained by ball milling.The particle size of HEA increases first and then decreases with milling time.After milling for 30 h,HEA particles are ellipsoid with particle size ranging from20μm to 30μm.The wettability of CoCrFeNiW_x high entropy alloy powder and WC is good.After sintering at 1400℃,the grain size of WC-CoCrFeNiW_0.2 and WC-CoCrFeNiW_0.5cemented carbides decreases with the increase of HEA binder content,and the Vickers hardness also decreases.However,the fracture toughness and flexural strength of the two WC-HEA cemented carbides show an increasing trend.With the increase of sintering holding time,WC grains grow up,and the hardness of cemented carbide decreases,while the fracture toughness and bending strength increase slightly.When the sintering temperature gradually increases from1300℃to 1450℃,HEA completely melts into liquid phase to better wet the WC grain surface.At this time,WC-HEA cemented carbide has high density,which improves the comprehensive properties of cemented carbide.The WC-10CoCrFeNiW_0.2 cemented carbide has the best comprehensive properties,and density,vickers hardness,fracture toughness,bending strength are97%,1785 HV₃₀,10.6 MPa·m^1/2,1373 MPa.Because HEA has good thermal stability and is not easy to be oxidized at high temperature,WC-HEA cemented carbide has good oxidation resistance.At 600℃,the oxidation products of WC-HEA carbide are WO₃,Ni WO₄ and CoWO₄.When the oxidation temperature rises to 700℃and 800℃,the contents of CoWO₄ and Fe₂O₃ on the oxidized surface of cemented carbide increase.The oxidation products of WC-HEA are fine Ni WO₄,CoWO₄ and Fe₂O₃.The oxidation product of WC-Cois CoWO₄,which has a larger thickness and more cracks.At the same temperature,the oxidation weight gain curve gradually flattens with the increase of binder content.WC-14CoCrFeNiW_0.2 cemented carbide has the best oxidation resistance.At room temperature,with the increase of HEA binder content,the friction coefficient of WC-HEA carbide increases,but the wear resistance decreases slightly.At high temperature,WC-HEA cemented carbide has higher high temperature hardness than WC-Cocemented carbide.With the increase of the experimental temperature,the wear mechanism of WC-HEA carbide gradually changed from abrasive wear to adhesive wear and oxidation wear.At the same temperature,the wear resistance of WC-HEA cemented carbide prepared by HEA binder is better than that of WC-Cocemented carbide prepared by the same process.