Research On Surface Repair Technology Of Rotating Shaft Roller By Laser Cladding Assisted By Electric And Magnetic Composite Field

Roller is an important component of rolling mills,and its surface may crack,peel off,or wear out during service.Currently,surface repair techniques for rollers include electro-brush plating,thermal spraying,and hot spray welding.However,these surface repair techniques produce coatings with defects such as cracks,pores,slag inclusion,and detachment.Therefore,laser cladding technology with low dilution ratio,small heat-affected zone,and good metallurgical bonding between the coating and the substrate is adopted to repair the roller surface.However,the coatings prepared by laser cladding surface repair technology have problems such as pores,cracks,and compositional segregation in practical applications.This article proposes a new process of electric-magnetic composite field-assisted rotating shaft laser cladding for preparing coatings to solve the problems of multiple pores,uneven distribution of microstructure and composition in high chromium cast iron cladding layers.Firstly,the electric-magnetic composite field-assisted rotating shaft laser cladding experimental platform is built through theoretical analysis,scheme design,and threedimensional modeling.Secondly,the electric-magnetic composite field-assisted rotating shaft laser cladding experiments are carried out based on the optimal laser cladding process parameters.Finally,various characterization and detection methods are used to analyze the experimental results,explore the influence of the external energy field on convection,heat transfer,and mass transfer in the laser melting pool solidification process,and clarify the influence mechanism of the external energy field on the distribution of microstructure and compositional segregation.The main contents are as follows:(1)Analyze the influence of electric and magnetic composite fields on laser molten pool convection,heat transfer,and mass transfer.Clarify the generation of laser molten pool and the mechanisms of convection,heat transfer,and mass transfer in the molten pool.Analyze the influence of Marangoni flow caused by different surface tension due to temperature difference,gravity,and buoyancy on molten pool convection behavior.Explore the influence of induced molten pool flow under the action of electric and magnetic composite fields on nucleation and crystal growth processes.Based on the characterization results of the composite energy field coating,the influence mechanism of energy field assistance on the microhardness and friction and wear properties of the cladding layer was revealed.(2)Build an experimental platform for combined electric and magnetic fields and conduct experiments.Based on the existing IPG 10 kw fiber laser melting equipment with a wavelength of 1.07μm,a stable magnetic field device with adjustable magnetic field intensity,an alternating current device with controllable electric field intensity,and a PLC intelligent control auxiliary device were designed to ultimately construct an experimental platform for combined electric and magnetic fields and assisted rotational axis laser melting.Using the comprehensive scoring method and orthogonal experiments,with laser power,scanning speed,and powder feeding rate as research objects,and the coating aspect ratio and dilution rate as evaluation criteria,the optimal combination of laser processing parameters for high chromium cast iron cladding was obtained.That is,laser power 1200 W,scanning speed 360 mm / min,powder feeding rate 15 g / min.On this basis,experiments were carried out to prepare high chromium cast iron coatings with electric and magnetic field-assisted rotational axis laser melting.(3)Explore the influence of combined electric and magnetic fields on coating structure evolution and composition segregation.Coupled laser melting experiments were carried out with magnetic and electric fields.In order to investigate the mechanism of energy fields on the influence of the melting layer,samples with fixed current parameters and changing magnetic field parameters were selected for analysis.Optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD)were used to detect and analyze the morphology,phase composition,and degree of component segregation of high chromium cast iron coatings under energy fields.The mechanism of nucleation and growth of crystals during the solidification phase transition of the melt pool was investigated.Based on the characterization results of the coating structure refinement and component distribution under combined energy fields,the influence mechanism of the energy field assistance on the microhardness and friction and wear properties of the coating was revealed.