Study On The Repair Technology Of Hot-Wire Laser Cladding For Switch Rail

China has built a railway network that extends in all directions.Facing problems of damage to switch rails,traditional manual repairing methods have low repair efficiency and can not form a good metallurgical combination between the repairing layer and the switch rails.In-depth analysis of the damage mechanism of the switch rails and modern surface repair technology,the hot-wire filling laser cladding is used to repair it.After repair,the cladding layer can form a good metallurgical bond with the switch rails,and the hardness of the cladding layer meets relevant technical standards,which can extend the service life of the switch rails and reduce maintenance costs.Firstly,through comparative analysis,A set of filling hot-wire laser cladding repair devices was constructed with fiber laser,Kuka welding robot,resistance heating coil,DC temperature control box,TIG welding wire feeder,and wire guide mechanism.And the motion program was written for laser cladding repair,realizing the laser cladding repair parameters controllable,wire preheating temperature adjustable,accurate and stable filling,and so on,so as to ensure the automatic repair process.Secondly,a single-pass fusion repair test was conducted on the surface of the damaged switch rail using lateral wire filling.The technological parameters of singlepass cladding repair were optimized by observing the macroscopic and microscopic morphology of the single-pass cladding layer.The optimized parameters are a wire filling angle of 40 °,wire preheating temperature of 200 ℃,laser power of 2300 W,wire filling speed of 27 mm/s,scanning speed of 23 mm/s,and protective gas volume of 15 L/min.At this power,the surface of the single-pass cladding layer is smooth and uniform.There are no defects such as pores,inclusions,and cracks,and the structure is good.Multiple laser cladding was performed on the surface of the pointed rail by using single-pass cladding repair optimization process parameters.The optimized overlap rate was 50 %.The repair method is homogenous cladding repair.After repair,the lap between the adjacent of two cladding layers is good,the overall fluctuation of the multicladding layer is not obvious,and there is no porosity,cracks,inclusions,or other defects in the cladding layer.In the multi-layer cladding repair,the same direction is used.Laser irradiation in the gap between the two cladding layers of the lower layer,the lower cladding layer melts and spreads out,and the melted wire is filled into the melting pool so that the multi-layer cladding layer has a higher flatness than the singlelayer cladding layer.Finally,tempering experiments and performance testing were conducted on samples taken from the laser cladding layer.There is a tempering effect between laser cladding layers,which can improve the microstructure of the cladding layer and reduce its hardness;At the temperature of 600 ℃,the martensite structure in the cladding layer basically disappears,and the structure is tempered sorbate.The internal hardness of the cladding layer is uniform,with an average hardness of 330 HV,which meets the national rail repair standards.