Study On Microstructure And Wear Properties Of Laser Cladding Coating On Wheel Materials

Laser cladding technology is a new type of surface treatment technology.The cladding material has a crucial influence on the coating performance.The Fe-based alloy powder is one of the most widely used cladding material.Therefore,through laser cladding treatment on wheel material surface,the optimization study on laser cladding Fe-based alloy coatings are beneficial to the extension of service life of railway wheel.In this paper,laser cladding is applied to the surface of the wheel material.Firstly,the microstructure,surface hardness and stress state of the Co-based and Fe-based alloy coatings were studied.The friction and wear properties of the two types of coating materials were evaluated via rolling friction and wear tests.Then,different coatings were produced thorugh adding different proportions WS₂,CaF₂,h-BN and CaF₂Then the microstructures,surface hardness and residual stresses of coatings were analyzed.The friction and wear properties of the WS₂/CaF₂/Fe coatings and h-BN/CaF₂/Fe coatings were evaluated via the wear tests.The conclusions of the study are as follows:(1)Fe-based alloy coating was mainly composed of(Fe,Ni)and Cr₇C₃ phases with coarse grains.Laser cladding Co-based alloy coating is mainly composed of?-Co phase and Cr₂₃C₆ phase.The residual stress of the sample along the rolling direction was compressive stress,and the residual compressive stress of the Co-based alloy coating was significantly greater than that of the Fe-based alloy coating.(2)After the laser cladding,the wear rate of the wheel sample was significantly reduced.The Co-based alloy coatings suffered the mildest damage with slight spalling;the Fe-based alloy coating surface had small cracks and furrows,and poor wear resistance.(3)WS₂/CaF₂/Fe coating structure mainly consist of(Fe,Ni),Cr₇C₃ and Cr S;h-BN/CaF₂/Fe coating structure mainly consist of(Fe,Ni)and Cr₇C₃.When the mass ratio of Fe-based powder,h-BN and CaF₂ was 98:1:1,the grains of the coating structure were finer.The residual compressive stress of WS₂/CaF₂/Fe coating increased with the increase in WS₂content.The residual compressive stress of h-BN/CaF₂/Fe coating was slightly higher than that of Fe-based alloy coating.When the mass ratio of Fe-based powder,h-BN and CaF₂ was98:1:1,the residual compressive stress of cladding coating reached the largest value.(3)With the content of WS₂ increased,the friction coefficient of the WS2/CaF2/Fe coating decreased,and the wear rate decreased firstly and then increased.When the content of WS₂ was 6%,the wear resistance of the coating was the best.In h-BN/CaF₂/Fe cladding coating,the addition of h-BN/CaF₂ had a positive effect on reducing the friction coefficient of the coating.When the mass ratio of Fe-based powder,h-BN and CaF₂ was 98:1:1,the laser cladding wheel specimen had the lowest friction coefficient and best anti wear performance.