Study On The Laser Additive Remanufacturing Technology Of Axle Holding Box

The axle box is an important part of the driving device of locomotive,which has the functions of fixing the traction motor,connecting the axle gearbox,and carrying the axle.After working for a period of time,there may be wear on the bearing holes of the axle box.During locomotive maintenance,once the size deviation is found,it must be replaced,thereby increasing the operating costs of railway transportation enterprises.This article focuses on the reparation of oversize of the axle box,using ZG230-450 material as the object.Through the design of laser remanufacturing cladding experimental process parameters,single-layer and multi-layer multi pass cladding experiments were conducted on the surface of 25 steel by cladding 316L stainless steel.Finally,the repair of the inner wall surface of the axle box bearing hole was successfully achieved.The main results are as follows:（1）Through a single pass cladding experiment,the process parameters for laser remanufacturing 316L stainless steel with dense structure and excellent morphology were determined to be laser power 1800 W and scanning speed 520 mm/min.（2）The microstructure of the 316L cladding layer is mainly composed of austenitic columnar crystals,with crystal orientation parallel to the direction of heat dissipation.With the decreasing cooling rate,the microstructure of the cast steel heat affected zone adjacent to the molten pool,changes from lath martensite to ferrite+sorbite or ferrite+pearlite.The hardness of the cladding layer fluctuates between 420 HV_0.2 and 470 HV_0.2,while the hardness of the heat affected zone of the substrate ranges from 190 HV_0.2 to 257 HV_0.2.The lower the laser power,the higher the scanning speed,the faster the cooling speed,the smaller the grain size,and the higher the microhardness.The tensile strength of the 316L cladding layer is 458 MPa,with low plasticity.（3）The installation hole of the axle box bearing was successfully repaired using laser remanufacturing cladding process parameters with a laser power of 1800 W,scanning speed of 520 mm/s,and powder feeding rate of 14 g/min.