| Fe-based amorphous/nanocrystalline soft magnetic material is a new type of green energy saving material due to its lower loss than traditional soft magnetic material.In the process of motor remanufacturing,replacing the traditional silicon steel material with amorphous material is a common and effective technology.The forming condition of the amorphous material itself is more demanding.In addition,due to the variety of motors,it is difficult to achieve unified manufacturing of stator and rotor models.Therefore,how to develop amorphous soft magnetic materials which can be widely used in the remanufacturing of electric motors presents important theoretical and application value.The soft magnetic amorphous/nanocrystalline coatings were prepared on the surface of silicon steel by thermal spraying.The spraying parameters selected in the experiment directly determine the comprehensive performance of the coating,so the comprehensive performance of the coating can be improved by optimizing the parameters.Based on FeSiB amorphous system,the comprehensive performance of soft magnetic coating can be improved by adding trace elements,so that amorphous soft magnetic material can be applied in the field of motor remanufacturing.The first two experiments in this paper were conducted to compare the performance differences of FeSiB amorphous/nano coatings deposited by subsonic flame and supersonic flame.According to the difference of heat source temperature and molten particle velocity,the reasons of different properties were analyzed.FeSiB amorphous/nano and FeSiBNbCu amorphous/nano coatings were prepared by supersonic flame spraying with different spraying powders.The influence of different elements in powder on soft magnetic properties of coating was investigated.The main research results and conclusions are summarized as follows:(1)select subsonic flame spraying process,combined with existing research reports.The coating was prepared with "oxygen flow rate,propane flow rate" as independent variable and coating amorphous content as dependent variable.The optimized parameters were propane flow 1.2m3/h and oxygen flow 1.1m3/h.By optimizing the process parameters,the soft magnetic coating has higher amorphous content.The component elements in the coating are evenly distributed,the coating surface is relatively dense,but there is still an obvious area of unmelted saturation.During the spraying process,the coating will inevitably oxidize.(2)in the process of heat treatment,compared with the powder,the crystallization of the amorphous coating needs to absorb more heat,its thermal stability is better than the powder,in addition,the coating in the process of heat treatment is easier to precipitate the ?-Fe phase rather than FeB phase,which is conducive to the improvement of soft magnetic properties.The maximum saturation magnetization of the coating is 182.85emu/g,and exchange bias occurs in the coating,possibly due to the doping of oxygen during spraying.(3)soft magnetic amorphous coating is prepared on silicon steel substrate by HVOF spraying process."Oxygen flow rate,propane flow rate,spraying parameters" was taken as the influence term of coating amorphous content after optimizing spraying process parameters.The optimal parameters are:propane 1.5m3/h,oxygen 0.7m3/h,spraying speed 300mm/s.The coating prepared with optimized parameters had the highest amorphous content,which was close to that of powder.Among the three parameters,oxygen is the most significant factor.The coating prepared by the optimized process is close to the amorphous content of the powder.At the same time,the distribution of elements in the coating is uniform,without the phenomenon of bias.Oxygen is doped into the coating during the spraying process.During annealing,the coating prepared by HVOF precipitates out crystals in the form of primary crystallization.The coating showed high activation energy(173.26kJ/mol?388.49kJ/mol),and had good stability.At the same time,the initial crystallization activation energy(173.26kJ/mol?187.39kJ/mol)is lower than the second crystallization activation energy(336.72kJ/mol?379.95kJ/mol),indicating that the coating can obtain the nanocrystalline phase with small size through annealing process.(4)compared with the reported crystalline soft magnetic coating,the coercivity of the coating deposited by HVOF in the experiment was smaller.At the same time,the doping of oxygen element in the spraying process will lead to the exchange bias of the coating.After the coating was annealed at different temperatures,it was found that the hoe-fe phase was firstly precipitated from the amorphous phase,and the magnetic induction intensity of the coating increased.However,with the continuous increase of annealing temperature,Fe-B phase began to separate from the amorphous phase,deteriorating the soft magnetic properties,resulting in the increase of coercivity of the coating.(5)soft magnetic coating was prepared on the surface of silicon steel by HVOF technology.The influence of Nb content on the phase structure and magnetic properties of the coating with Fe content Fe83Si(8-x)B8NbxCu1(x=1,2,3,4at.%)was systematically studied.The grain size in the powder decreases with the increase of Nb content,but this phenomenon will disappear when the Nb content exceeds 3 at.%,that is,the restriction of Nb element on grain size will not be raised all the time.At the same time,Nb element has a certain inhibitory effect on the precipitation of FeB phase,but when the Nb element exceeds a certain value,the precipitation of FeB phase will occur in the powder.Compared with powder,the coating prepared by HVOF spraying has smaller grain size,and some nb-rich areas will be generated in the coating,and the precipitation of FeB phase in the coating will be inhibited with the increase of Nb elements.(6)in the powder,when X=1,the powder shows the maximum saturation magnetization,which is about 0.173 emu/mg.With the increase of Nb content,the saturation magnetization first decreases and then increases.The reason is that the addition of Nb elements will affect the size of grain in the powder,thus affecting the magnetic properties of the powder.Compared with powder,the overall saturation magnetization of coating prepared by HVOF coating is low.This is mainly due to the production of more FeB phase in the coating.On the one hand,the production of FeB phase reduces the content of steno ?-Fe phase in the powder,while steno ?-Fe phase has a higher magnetic induction intensity.On the other hand,FeB phase is a non-magnetic compound,and the production of this compound will worsen the Ms value of the alloy,resulting in a lower Ms value of the alloy.At the same time,it has a large magnetic anisotropy.In addition,exchange bias occurs in the coating. |
PDF Full Text Request