| Hydraulic support column is a vulnerable part of hydraulic support equipment in underground coal mine,which is prone to wear,corrosion and other phenomena in underground environment,resulting in the failure of hydraulic system.Therefore,the surface of the column should be strengthened.The traditional surface repair process is chromium plating and laser cladding,the former is easy to produce chromium containing wastewater and waste gas,causing pollution;The latter uses cladding powder with high cost and long cycle.Therefore,in this paper,cladding welding is used to replace chromium plating and laser cladding,and stainless steel tube is used to replace electroplating solution or powder to strengthen the column surface.In this paper,the packing welding layer prepared by different process parameters is the main research object.Through the optical microscope,X-ray diffraction analyzer,UMT wear tester,electrochemical workstation and micro-scratch tester,the comparison and analysis of electroplating chromium and laser cladding The microstructure and mechanical properties of the coating and cladding weld layer,as well as the influence of process parameters on the structure and mechanical properties of the cladding weld layer,were studied.The results of the study are as follows:(1)There are three main phases of electroplated chromium coating,namely Fe-Cr phase,Cr SO4 phase and Cr2O3 phase.The microstructure of electroplated chromium coating mainly contains ferrite and pearlite,with clear grain boundaries,fine grains,and denser structure.The chromium electroplating process changes from the hardness of the"substrate-coating"to:firstly,the hardness of the substrate remains basically unchanged,the hardness is 231.0HV,and the milky white chromium layer increases rapidly in the middle,and then the hard chromium coating remains basically stable,the hardness is 610.5HV.(2)The phases contained in the laser cladding coating are Fe Ni3 phase,Ni2Si phase and Cr phase.The structure of the laser cladding layer is mainly a large number of lamellar pearlite,which is a layered complex formed by alternately laminating ferrite thin layers and cementite thin layers.The hardness of the laser cladding process from"substrate-coating"is basically unchanged at the substrate first,the hardness is 233.3HV,and then increases rapidly,and finally the higher coating hardness remains unchanged,the laser cladding coating hardness is 534.2HV.(3)The cladding solder layer has?N diffraction peaks at the lower angles(111)and(200)of the diffraction peak.In the cladding solder layer,the nitride phases produced are mainly Fe4N and Cr N.The structure of the cladding weld layer is composed of a single austenite structure(?phase).The austenite is composed of equiaxed polygonal grains with relatively fine grains and irregular arc-shaped grain boundaries.(4)Through comparative analysis,it is found that the amount of wear of the electroplated chromium layer is the smallest,which is 0.0325±0.0026g.The electroplating chromium layer exhibits better wear resistance than laser cladding and packing welding.performance.The corrosion rates of the laser cladding and cladding weld layers are both very small,3.04±0.12mg and 2.62±0.21mg,respectively.The cladding weld layer exhibits excellent corrosion resistance.The critical loads of the electroplated chromium coating and the packing welding layer are 3.96N and 4.67N,respectively,indicating that the bonding performance of the packing welding layer and the substrate is better than that of the hard chromium plating layer and the substrate.(5)When the inlay melting temperature increases from 400°C to 700°C,as the temperature gradually increases,the grain size shows a continuous increase;as the temperature continues to rise,the hardness of the cladding solder layer changes A gradual downward trend appears;with the gradual increase of the inlay melting temperature,the wear amount corresponding to the packing welding layer increases.When the temperature is 400°C,the minimum wear amount is 0.0563±0.0013g.When the insert melting pressure increases from 35MPa to 50MPa,as the pressure gradually increases,the grain size shows a gradual decrease;when the pressure increases from35MPa to 45MPa,the hardness value gradually increases,when the pressure is 45MPa When the pressure reaches the maximum value of 507.0HV,when the pressure continues to increase to 50MPa,the hardness decreases.When the pressure is 35MPa,the relative wear rate of the packing welding layer is the highest,and the wear resistance is worse.When the pressure is 45MPa,the relative wear rate is the smallest value,which is 2.917×10-3;as the pressure increases.The greater the critical load of the overlay welding layer,the increase in pressure can better improve the bonding force between the coating and the substrate,and increase the service life of the coating material.Under different nitriding treatment times,?N diffraction peaks appear at the lower diffraction angles(111)and(200).As the nitriding treatment time increases,?N(200)will gradually increase,especially when the nitriding treatment is 5h The diffraction peaks are significantly higher than the diffraction peaks when the nitriding treatment time is 2-4h respectively.The nitride phases are mainly Fe4N and Cr N.With the increase of the nitriding time,the diffraction peaks of the two nitride phases gradually increase;As the nitriding treatment time increases,the hardness of the coating will gradually increase;as the nitriding time increases,the relative wear rate of the coating becomes smaller and smaller.The influence of nitriding time on the wear performance gradually becomes smaller as the time is longer;as the nitriding treatment time increases,the corrosion weight loss and corrosion rate of the coating gradually decrease,indicating that the longer the nitriding treatment time,the more helps improve the corrosion resistance of the coating. |
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