Study On Microstructure And Properties Of Cr₃Si Reinforced Superalloy Based Wear Resistant Composite By Plasma Melting And Deposition Manufacturing

Cold extrusion dies for copper alloy feedstock of high-speed rail contact wires usually work under harsh conditions with high contact stress,high temperature and severe wear.The service life of dies is relatively short,which results in low yield and unstable quality of contact wires.To meet the working conditions of continuous cold extrusion dies material,high temperature wear resistant composite was fabricated by coaxial powder feeding plasma melting and deposition technology.The composite is based on wrought superalloy Inconel 718 as the matrix and reinforced by transition metal silicide Cr3Si with high temperature wear resistance.According to Cr-Si binary phase diagram,Inconel 718-67.2Cr-12.8Si(wt.%),Inconel 718-58.8Cr-11.2Si(wt.%),Inconel 718-50.4Cr-9.6Si(wt.%)and Inconel 718-42Cr-8Si(wt.%)four alloy powders were designed.Using these alloy powders and pure Inconel 718 powder as raw material,Cr3 Si reinforced superalloy based wear resistant composite and comparative sample Inconel 718 were fabricated with optimized process parameters.XRD,OM,SEM,EDS material analysis methods were used to analyze the phase composition and microstructure of the plasma melt and deposited Inconel 718 sample and composite.The results show that Inconel 718 sample mainly consists of γ"-Ni3Nb high temperature reinforcement and y-(Ni,Fe)solid solution.The composites are composed of Cr3Si,Cr13Ni5Si2 and y-Ni based solid solution.The microstructure of the composite material is fine and dense,Cr3Si reinforcements distribute uniformly in the y-Ni based solid solution matrix.The volume fraction of Cr3Si primary phase in microstructure decreases with increasing Inconel 718 contents in the powder.The hardness of the composite was measured using a microhardness tester.The results show that the fabricated composites perform higher hardness and the values increases with increasing Cr3Si contents.The dry sliding friction and wear properties of composites at room temperature were tested by pin-on-disk wear tester.Composites exhibit excellent wear resistance under ambient temperature dry sliding wear conditions.The volume fraction of Cr3Si in composites has a significant effect on the wear resistance.The higher the volume fraction of Cr3Si,the better the wear resistance of composites and the lower the friction coefficient during wear process.Ball-on-disk high temperature wear tester was used to test the dry sliding friction and wear properties of composites at high temperature.Under high temperature dry sliding wear conditions,Inconel 718 sample has poor wear resistance,with severe adhesive wear and a large area of surface material falling off.Cr3Si has higher elevated temperature hardness,excellent high temperature oxidation resistance and unique chemical bonding properties in which covalent bonds coexist with metal bonds,which makes the composites have the ability to resist abrasive wear and adhesive wear.The composite material exhibits good high temperature friction and wear properties.During the room temperature and high temperature wear process,Cr3Si reinforcements fully play a role of anti-wear backbone.The high volume fraction of Cr3Si reinforcements in composites will lead to a decrease in toughness,so the content of reinforcements should not be too high.The composite fabricated using Inconel 718-50.4Cr-9.6Si(wt.%)alloy powder as raw material has good comprehensive performance and can be applied under high temperature and heavy wear conditions.