Research On The Microstructure And Properties Of Fe60 Coatings By Composite Field Assisted Laser Cladding

Laser cladding is a high-energy heat source for rapid heating and melting,and the rapid cooling process after the spot removed,in the process of rapid cooling coating and substrate thermal dilatation coefficient,Young's modulus,thermal conductivity is different,and high metal solution viscosity and other reasons,maybe formation of cracks,pores and other defects,for the defects will reduce the life of the coating or its use of performance,even make the coating can't be used,this will bring about unnecessary economic loss of production,and the use of the process to bring security risks.According to the above characteristics,this paper designs a compound field based on the characteristics of mechanical vibration and magnetic field.The Fe60 alloy coating was prepared by laser cladding on 45 steel surface.The coating morphology and the depth of the heat-affected zone were characterized by OM and SEM to the composite field-assisted laser cladding coating.Except the two kinds of test methods above,the phase composition and crystal structure of the coating were characterized with XRD and EDS,and the Hardness and corrosion resistance of the coating were tested.In addition,based on the above tests,the relationship between the coating topography and the depth of the heat-affected zone in the compound field is discussed,and the influence of the compound field on the coating defects is analyzed,and why compound field can improve the microstructure of the coating is studied.The surface quality of the coating and the microstructure of the coating were improved obviously under the condition of the maximum of 3.2 A,and amplitude of 3 gears?vibration frequency fixed to 100 Hz?.When the auxiliary field is not applied,the depth of the heat-affected zone is 845?m,the maximum state of the composite field is 590?m,the vibration 3 gears is 519?m,and the excitation current 3.2 A is 580?m.Although the effect of the complex field on the depth of the heat-affected zone is obvious,it is weaker than the single time.The composite field also helps to reduce the number and length of cracks in the coating.The microstructure of the coating consists of cytoplasmic crystal,dendritic crystal and isometric crystal,and the most of the cytoplasm is the bottom layer.However,the addition of the auxiliary field has the function of refining grain,and it can also change the cell-like crystal and dendrite into isometric grains,by comparison,it is found that the effect of the vibration field on the bottom refinement of the coating is obvious in the upper part,so that the cell-shaped crystal at the bottom of the coating can be refined to form isometric crystals or the dendrite will be interrupted into a short dendrite,and grain refinement is also present in the coating.The effect of the magnetic field on grain refinement is opposite to that of the vibration field,and the upper part of the coating is more significant.The effect of the vibration field and the magnetic field can be enhanced by the compound field,and the refinement of the grains in the upper part of the coating can be strengthened.In addition,the compound field can effectively reduce the depth of dilution area.When the auxiliary field is 2.77?m,the vibration is 3 gear,the depth of the combined zone is 1.75?m when the steady magnetic field current is 3.2 A,and the combined zone depth is 1.94?m when the single vibration field is added.When with a single magnetic field,the depth of bonding region is 1.92?m,it can be seen that the effect of reducing the thermal penetration of a single magnetic field or a vibration field under the complex field condition.The auxiliary field does not change the phase structure in the coating,the phase structure of the coating includes Fe-Cr solid solution,?Fe,Ni?solid solution,Ni-Cr-Fe solid solution and Fe₂₃?C,B?₆ compounds,but the EDS results show that the auxiliary effect of the compound field is favorable to mass transfer and can improve the composite field can effectively refine the grains,improve the structure of the coating,and the mass transfer,and help to improve the coating performance.The micro-hardness and corrosion resistance of the coatings prepared under the complex field,the maximum micro-hardness is up to 702 HV_0.2,and the corrosion resistance is enhanced under single field or no auxiliary field conditions.