Morphology And Technology Of Laser Cladding Based On 45 Steel

45 steel material can be used for manufacturing plastic molds or high strength transmission components.Under poor working conditions,it would be frayed,oxidized,and corroded,which eventually leads to failure.Through laser cladding,the failed parts can be repaired,the service life of parts is extended,reducing waste of resources,and cost saving.In this paper,45 steel materials are taken as the research object commonly used in industry,laser cladding experiments are carried out on the surface of the substrate,and the macroscopic morphology of the cladding layers are improved by combining the theoretical models and the experiments,reduce cracks in the cladding layer,and improve the overall wear resistance of45 steel components.Firstly,the central composite design in response surface method is used to predict and optimize the geometry of single-layer.The width height ratio and dilution rate are used as indicators to study the variation of experimental parameters on the geometry of sedimentary layer.The optimized cladding layer morphology was tested by experiments.The results showed that the maximum error between the experimental value and the predicted value of the aspect ratio and dilution rate was 8.5%,and the optimized process parameters were:defocusing amount 14.4mm,laser power 1290W,powder feeding voltage 8.3V,scanning speed 3.7mm/s.The numerical simulation of the stress field of the laser cladding single-pass deposition track is carried out by the double ellipsoid heat source model.The heat source morphology is compared with the cross-section morphology of the single pass cladding layer,and the simulation accuracy is ensured by the method of heat source correction.The results show that the entire cladding layer as a whole mainly beared tensile stress,and the axial tensile stress is mainly in the direction.The maximum tensile stress appears at the end of the cladding layer at 532MPa.Secongly,in order to improve the surface quality of the multi-layer deposition layers,a theoretical model of multi-layer overlap ratio was established.The relationship between the multi-lap overlap rate and the width and height of the geometric features of the sediment layer was derived from the formula.The macroscopic morphology,cross-sectional morphology,and surface flatness are used as evaluation indicators to verify the accuracy of the theoretical model of the overlapping rate.It is,ultimately,concluded that the cladding layer quality is better when the overlapping rate is 45%-50%,which is consistent with the theoretical model The maximum error of the overlapping rate is 2.54%.The microstructure and phase analysis show that the element segregation in the coating and the unfavorable distribution of the hard phase are one of the reasons for the cracking of the nickel-based alloy coating.Finily,from the perspective of fracture mechanics and thermoelastic mechanics,the fracture criterion for cracking of nickel-based coatings is obtained.In order to reduce cracks in the cladding layers,an experimental method for crack suppression by a prefabricated mesh structure was proposed.Through the color flaw detection test and the cross-sectional morphology,the mesh range for suppressing cracking of the cracked nickel-based composite coating was obtained.To enhance the wear resistance of nickel-based alloys,choose to add 4% CeO₂ to the nickel-based composite coating with 14 mesh stainless steel mesh.By comparison,after adding Rare Earth Elements,the microhardness of the composite coating has been reduced to 386HV,but it is still 1.8 times that of the substrate.From the point of view of wear scar morphology and wear,the depth of wear scar was significantly reduced,and no bean-shaped pits were found.The wear was 0.56×10^-5mm³·N^-1·m^-1,which was lower than that of 45 steel 85.1%.It can be seen that after adding Rare Earth Elements CeO₂,although the microhardness of the 14 mesh 304 mesh Ni60 composite coating is reduced,the wear resistance of the composite coating is greatly improved,and at the same time the formation of the hard phase is suppressed,the toughness phase is more easily precipitated,The overall plastic toughness of the composite coating is improved,according to the Hall-Petch formula,the yield strength of the alloy coating is correspondingly reduced,thereby reducing the internal stress in the alloy coating and reducing the tendency of cracking.