| The rotor shaft of1.5MW wind-driven generator is expensive. The material ofthe rotor journal is35CrMo. Due to excessive wear and tear after working long time,the radial dimensions of the journal become too smaller to continue to work.Compared with replacing a new crank shaft, the repairing of rotor journal can extendits service life, is of great significance because of reducing costs and conservingresources. Laser cladding technology is done by adding some suitable claddingmaterials onto the substrate surface and then melting the materials and the substratetogether with high intensity laser beam. Compared with other surface modificationtechnologies, laser cladding has the following advantages: it can reduceheat-induced deformation, modify freely the substrate surface properties, clad easilythe workpiece with big area and realize metallurgical bonding between the claddingmaterials and substrate. This paper aims to repair the rotor journal by laser cladding.First, the basic principle of laser cladding process, including the interactionmodel of powder、laser beam and substrate surface,the molten pool formation theory,several aspects of the molten pool shape and the dilution rate model, is introduced inthis paper, which is the theoretical basis of laser cladding of rotor journal.Then, according to the usage requirements for the rotor journal after repaired,on the basis of analyzing the existing cladding materials and the general principlesof compounding powder, three kinds of nickel-based powder materials arecompounded, whose content of Fe are diferent from each other. Using these threekinds of nickel-based powder materials, cladding experiments with single-layer lapare carried out under suitable process parameters. After comparing themicrostructure, microhardness and surface appearance of the cladding layersobtained by using the above three kinds of materials, the final cladding material,with which the best cladding layer can be obtained, is determined for the nextmulti-layer and multi-pass lap cladding experiments.Finnaly, cladding experiments with multi-layer and multi-pass laps areperformed, and the corresponding microstructure and microhardness of the claddinglayers are analyzed.The experimental results show that by using the cladding material with middleiron content, not only in single-layer lap cladding, cladding layers with finemicrostructure, high hardness, no pores or cracks can be obtained, but also in multi-layer and multi-pass lap cladding, cladding layers with no seriousmicrostructure defects can be gained, which remain delicate microstructure and highhardness characteristics.In order to improve the wear resistance of the cladding layer, the surface of thesecond layer is remelted, which enable the cladding layer to obtain finermicrostructure, slight higher microhardness and better appearance.In all experiments, the cladding parameters such as the scanning speed,thedilution and the height and width of the cladding layer are empirically ortheoretically determined.Then the minimum overlap rate of the multi-pass cladding,which is an important parameter for multi-pass lap cladding, are defined. Thetheoretical values of the overlap rate calculated are in good agreement with theactual values used in practice. |
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