Study On Preparaties And Tribological Mechanism Of FeCoNiCr-X(X=Mn,V) High-entropy Alloy

As a new type of material,high-entropy alloy had the advantages of high strength,high hardness,excellent wear resistance,corrosion resistance,and high thermal resistance.It was an alloy material with good application prospects.In this thesis,the FeCoNiCr-X（X=Mn,V）high-entropy alloy was prepared by mechanical alloying combined with vacuum hot-pressing sintering technology,and the microstructure,mechanical properties and tribology performance under different conditions of the two high-entropy alloys were systematically studied.Research indicated:The relative density of bulk FeCoNiCr-X（X=Mn,V）alloy prepared by mechanical alloying combined with vacuum hot pressing sintering technology was above 99%.FeCoNiCr Mn high-entropy alloy was a single FCC phase with uniform surface.The average hardness of the alloy was183HV,the compressive strength of the material was 228MPa,and the tensile strength was 686MPa.The main phase of the FeCoNiCrV high-entropy alloy was the FCC phase,and a large number of protruding hard phasesσ（Cr-V）were precipitated on the surface.The average hardness of the alloy was 975HV,the compressive strength was726MPa,and the tensile strength was 237MPa.FeCoNiCr Mn high-entropy alloy had better tensile properties than FeCoNiCrV.The main fracture mode of FeCoNiCr Mn tensile was dimple-like ductile fracture;the main fracture mode of FeCoNiCrV tensile was brittle dissociation surface fracture combined with a small amount of dimple fracture.Under dry sliding friction conditions at room temperature,when counterpart was Si₃N₄,FeCoNiCr-X（X=Mn,V）high-entropy alloy had the best tribological performance,and was less affected by the load,and the wear rate is always the lowest,respectively 1.298×10^-4mm³/Nm,0.718×10^-4mm³/Nm,showing excellent wear resistance.For FeCoNiCr Mn/Si₃N₄,the main wear mechanisms were adhesive wear,slight fatigue wear and oxidative wear.For FeCoNiCrV/Si₃N₄,the main wear mechanisms were fatigue wear,adhesive wear and oxidative wear.In a high temperature environment,with the temperature increasing,the wear rate of FeCoNiCrV decreased significantly,and its high temperature wear resistance was better than FeCoNiCr Mn.Especially at 800℃,the wear rate of FeCoNiCrV was 20 times lower than FeCoNiCr Mn,and the wear rate was 0.289×10^-4mm³/Nm.The main wear mechanism of FeCoNiCrV high-entropy alloy from 25℃ to 200℃ was oxidative wear,adhesive wear and fatigue spalling.The degree of surface wear decreased with the increase of temperature.At 800℃,the wear mechanism was a single oxidative wear.Under deionized water conditions,the wear resistance of FeCoNiCrV was also better than FeCoNiCr Mn,and the wear rate ranged from 0.26g/m³to 0.3 g/m³.When the FeCoNiCrV alloy surface was hard,the boundary water film lubrication effect was obvious,and the anti-friction and anti-wear effect was obvious.The lubrication mechanism of FeCoNiCrV was boundary lubrication,the lubrication effect was obvious,and the main wear mechanism was micro-furrow wear.Under the condition of liquid paraffin lubrication,the wear rate of FeCoNiCr-X（X=Mn,V）was very low.The wear rate ranged from 0.07g/m³to 0.16g/m³,and from0.02g/m³to 0.03g/m³.Under the protection of oil lubrication,the wear resistance of FeCoNiCrV was still better.The lubrication mechanism of FeCoNiCrV was hydrodynamic lubrication.As the load increased,the micro-furrow wear of the wear machine turned into oxidative wear.