Study On Fe-b Bainite Steel Coating Fabricated By Laser Cladding

Pearlitic rail is one of the most widely used rails in railway at present,but its performanceimprovement is linit,which cannot meet the development trend of high-speed passenger transportation and heavy load freight transportation.Therefore,it is of great theoretical significance and application value to study the rail materials with good strength and good toughness and wear resistance.In this paper,high boron bainite steel was prepared by laser cladding,and the influence of Tiand Ce on the coating was studied.The following conclusions are drawn:（1）In the high boron bainite steelcoating,the main phases areα-Fe,Fe₂B and Fe₃（C,B）.With the increase of boron content,the microhardness of the coating increases gradually.And when the boron content is 5%,the hardness is about 901HV_0.2,which is 2.3 times of that of the bainite steel substrate coating.With the increase of boron content,the friction coefficient decreases gradually,the wear performance of 3%boron coating is the worst because it is near the eutectic point and forms a large number of coarse grid borides between the crystals.（2）The lattice boride is formed between the grains of the high boron iron base alloy,which greatly reduces the toughness of the matrix.In addition of Ti,TiC particles located at growth direction of boride,make the grid boride change into fine particle.Due to the formation of TiC,C element content in the matrix decreases,and the primary phase is changed into granular bainite during the solidification process.After adding the C,the primary phase of the matrix was changed into lath bainite mostly.After adding 0.6%boron,the microhardness of the coating was increased by 40.8%,but the toughness value decreased greatly.After adding TiModification,the toughness value increases.The fracture morphology of the cladding is changed from the honeycomb like to intergranular shape.And there is the coexistence of quasi cleavage surface and tearing edge in the fracture.（3）After the addition of Ce,the borides grid is broken.But with the increase of RE content,the modification effect is not obvious,the toughness value is also increased,and with the increase of Ce content,it first increases and then decreases.There are serious fatigue spalling and abrasive wear on the worn surface.After tempering,the effect of modification is much obvious,but there is no obvious change in toughness after rare earth modification.The main wear mechanism is fatigue spalling and the second is abrasive wear.