Preparation Of Plasma Cladding Fe-based Alloy Coating On Deep Loosening Shovel And Research On Their Wear Resistance

The wear and tear of key parts of agricultural machinery has severely shortened its service life,has a great impact on agricultural production costs,and has restricted the development of agricultural mechanization.With the implementation of the Northeast Black Soil Conservation Tillage Action Plan,subsoiling technology has been widely used as one of the main link of protective tillage,and the consumption of deep loosening shovel has been increasing year by year.Plasma cladding technology can prepare a coating with high wear resistance on the surface of the substrate material.While ensuring sufficient bonding strength between the coating and the substrate,the surface of the substrate can achieve the purpose of wear resistance.Excellent performance has become an important method to improve the wear resistance of key parts of agricultural machinery.In this study,plasma cladding technology was used to prepare Fe-Cr-C alloy coatings on deep loosening shovel,and the properties of the coatings were studied.The details are as follows:（1）Optimization of plasma cladding Fe-based alloy coating process parameters:the Fe-Cr-C alloy cladding coating was prepared on the surface of Q235 steel substrate by using plasma cladding technology,combined with range analysis and comprehensive scoring method,with the hardness and wear of the sample cladding coating as indicators,and the working current,Scanning speed,powder feeding speed,overlap rate and ion gas flow rate were test factors.Orthogonal experiments were carried out on the process parameters of plasma cladding Fe-Cr-C alloy coating,and the best combination of process parameters of Q235 steel plasma cladding Fe-Cr-C alloy coating was obtained.The optimized results of orthogonal experiment were:The working current and powder feeding speed had the most significant comprehensive influence on the hardness and wear of the plasma cladding coating.The best combination of process parameters was:working current 110A,scanning speed110mm/min,powder feeding speed 6r/min,overlap rate 40%,ion gas flow rate 1.0L/h.（2）Research on the microstructure of plasma cladding Fe-based alloy coating:the structure and phase composition of Fe-Cr-C alloy cladding coating were analyzed by scanning electron microscope（SEM）,energy spectrometer（EDS）and X-ray diffractometer（XRD）.Metallographic microscopic observation was performed on the cladding sample,and the metallurgical bond between the coating of the sample and the substrate was good,no pores and cracks,uniform and compact microstructure,mainly cellular crystals,dendrites and planar crystals,etc.The main hard phase of the coating was（Cr,Fe）₇C₃,and the remaining phases wereγ-Fe,（Fe,Cr）,（Fe,Ni）,（Fe,C）,（Fe,Ni）₂₃C₆,Cr₇C₃,Ni₃Si,Fe₃Mo and Fe₂Nb.（3）Research on wear resistance of plasma cladding Fe-based alloy coating:the distribution of microhardness of Fe-Cr-C alloy cladding coating was studied by microhardness test.Through friction and wear tests combined with ultra-depth-of-field microscope observations,the friction coefficient,wear volume,wear rate,wear volume,wear scar morphology and other wear properties of the cladding coating were studied.The average microhardness of the cladding coating of the sample with the best parameters reaches545.1HV_0.5,which was about 3 times higher than the hardness of the substrate.After 5h of wear test,the total wear of the optimal parameter sample was 0.25g,which was reduced by about 2/3 compared with the base.The wear volume was 45.09mm³,which was about 1/3 of the base wear volume.The wear rate was 1.22×10^-4mm³/（N·m）,which was about 1/3 of the base wear rate.The friction coefficient was 0.23,which was reduced by about 1/2 compared with the friction coefficient of the substrate.The hardness and wear resistance of the cladding coating had been significantly improved.（4）Research on the wear resistance of plasma cladding Fe-based alloy coating of deep loosening shovel:the Fe-Cr-C plasma cladding coating was prepared on the domestic deep loosening shovel made of Q235 steel with the optimal process parameters,and the soil friction and wear test of the subsoiling shovel was carried out on the soil abrasion testing machine.By analyzing the microstructure,microhardness,wear amount and wear scar morphology of the cladding coating of the deep loosening shovel,the friction and wear properties of the surface of the plasma cladding strengthened deep loosening shovel were investigated.The feasibility of applying this process and coating to key parts of agricultural machinery had been verified.The result showed:after plasma cladding deep loosening shovel specimens,the average microhardness of the Fe-based alloy coating was 537.1HV_0.5.Compared with the untreated deep loosening shovel substrate specimens,the microhardness was increased by about 3 times.After 12 hours of soil friction and wear test,the deep loosening shovel base specimen and cladding specimen had experienced a grinding process of about 77.4km.The wear mechanism of the two deep loosening shovel specimens was scratch abrasive wear,weightlessness30.704g and 16.488g respectively,accounting for 3.32%and 6.52%of the total weight.The deep loosening shovel specimen strengthened by plasma cladding had a 1.86 times increase in wear resistance compared with the base specimen,and it had good economic efficiency.Plasma cladding significantly improved the wear resistance of Q235 deep loosening shovel.