| With the high-speed development of railway transportation industry,the requirements of high-speed trains for bearing performance are increasing day by day.The corrosion and wear peeling of bearing working surface account for a large proportion in bearing failure.Therefore,new surface strengthening technology is introduced to make new materials form a new metal strengthening phase on the working surface,improve the performance indexes of bearing working surface and prolong the service time of bearing.The most effective way to improve the surface properties of materials is to use surface treatment technology to spray and modify the surface.EDM technology will not only produce dense metallurgical bonding layer,but also quickly heat and cool the fine microstructure,which is widely concerned by researchers.In this paper,based on the experimental research on the properties of cemented carbide coating deposited by EDM,the following work is carried out:(1)Using high carbon chromium bearing steel as the base material and two different grades of cemented carbide as the electrode material,and taking the three influencing factors of discharge voltage,discharge frequency and specific deposition time as the test variables,the single factor test scheme under different processing conditions is designed.The test data such as the distribution of main elements in the section,coating hardness and coating section morphology are measured,and the effects of different process parameters on the above test indexes are analyzed.The results show that with the increase of voltage,the mass transition coefficient and coating hardness increase first and then decrease,and the section quality becomes worse gradually;With the increase of frequency,each index shows an increasing trend;When the specific deposition time increases,the coating hardness first increases and then decreases,the section quality first increases and then decreases,and the mass transition coefficient continues to decrease.(2)The dry friction test was carried out on the samples before and after processing by using the ring block wear tester,and the advantages and disadvantages of wear resistance were compared by single factor test.The wear of the coating was observed and analyzed by three-dimensional topography instrument and scanning electron microscope,showing the specific advantages of high hardness alloy coating in friction resistance.The results show that the wear resistance of cemented carbide coating is significantly better than that of bearing steel substrate,and the surface wear mark depth and wear volume are significantly reduced.With the increase of voltage and specific deposition time,the maximum wear mark depth and wear mark volume first decrease and then increase,while they are always in a small trend with the increase of frequency.(3)By simulating the acid environment of material corrosion,the low concentration acid solution is selected for corrosion test,and the changes of coating surface roughness and coating quality after corrosion are measured.The advantages of cemented carbide materials with high corrosion resistance as surface deposition layer are compared,and the change law of coating corrosion resistance is analyzed.The results show that the corrosion resistance of cemented carbide coating is much higher than that of bearing steel substrate,and when the voltage increases,the change of roughness and coating quality first decrease and then increase,while both show a downward trend when the frequency and specific deposition time increase.The research results have important guiding significance for improving the service life of axle box bearing of rail train,increasing service safety and reducing production and maintenance cost. |
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