Arc Additive Preparation With Synergistic Powder And Wire,Microstructure And Properties For WC_P Reinforced Wear-Resistant Layer Of Agricultural Cutting Tools

The application of agricultural machinery has greatly improved the efficiency of agricultural production.In recent years,the comprehensive mechanization rate of crop cultivation and harvest has been increasing.However there is still a significant gap in the service life of domestic agricultural machinery cutting tools compared to advanced foreign levels.Due to the wear and impact of soil sand and gravel in the work,the service life of agricultural machinery tools and other components that touch the soil is greatly reduced,which has become the main reason for the failure of agricultural machinery.The wear-resisting layer containing WC particles prepared on the tool surface can effectively improve the wear resistance of the surface and prolong the service life of the tool.In this paper,the applicability of traditional surface modification technology for agricultural tools and the microstructure and properties of the prepared wear-resistant layer are analyzed and compared.The arc additive preparation method with synergistic powder and wire for preparing WC_Preinforced wear-resistant layer of agricultural tools is proposed.The arc additive preparation method with synergistic powder and wire uses arc as heat source and flux-cored welding wire as filling material.The content of WC particles in wear-resistant layer was further increased by coaxial powder feeding,which can achieve the preparation of a high volume WC fraction wear-resistant layer.OM,XRD,SEM,EDS and other equipment were used to analyze the microstructure,phase composition and element distribution of the wear-resisting layer prepared by the traditional preparation method and the arc additive preparation method with synergistic powder and wire.And the hardness of the wear-resisting layer was tested by microhardness tester.The results show that:（1）The heat source temperature of oxy-acetylene flame surfacing is low,which is conducive to reducing the decomposition of WC particles.However,this method has low efficiency and is difficult to realize automation.WC particles were evenly distributed in the wear-resisting layer prepared by oxygen-acetylene flame surfacing.And the volume fraction of WC particles reached 60%.There are W₂C,WC and Fe₃W₃C phases in the wear-resistant layer.The gray block phase in the matrix and transition layer are Fe₃W₃C phases.（2）The heat source temperature of Oxy-acetylene flame spray welding is low and the method is easy to achieve automation.The disadvantage of this method is the serious loss of powder during cladding.The distribution of WC particles in wear-resistant layer is not uniform.It is not easy to separate multiple workpieces when cladding large area.The volume fraction of WC particles in the upper part and the lower part of the wear-resisting layer prepared by oxyacetylene flame spray welding is about 55%and 20%respectively.The grain edge is composed of rod-like WC structure and transition layer.And the transition layer and the gray massive structure distributed on the matrix are Fe₃W₃C phase.（3）WC_Preinforced wear-resisting layer prepared by laser cladding has good forming quality.The method has a high degree of automation.However its heat source temperature is extremely high,which will seriously cause decomposition of WC particles in the wear-resisting layer.Therefore,the volume fraction of WC particles is only about 10%.And there are a large number of M₇C₃phases composed of chunks and strips appear on the matrix.（4）Plasma cladding method has high efficiency and good wear-resisting layer forming.However,its high temperature of heat source will lead to a large amount of decomposition of WC particles.The decomposition degree of WC particles under the wear layer is higher,and the morphology is gray massive Ni₁₇W₃phase around the center of unmelted WC.The distribution of Ni₁₇W₃phase in the upper block of the wear layer is more uniform.（5）TIG arc has a moderate heat source temperature and TIG welding can can achieve automation.However,this method has high requirements on welding process and high cost.In the wear-resistant layer prepared by TIG surfacing,the unfused WC particles are distributed in the lower part and the size change is not significant.There are a small amount of Fe₃W₃C phases and a large amount of fishbone Fe₃W₃C phases on the matrix.（6）The heat source temperature of arc additive preparation method with synergistic powder and wire is moderate,which will cause the low decomposition degree of WC particles.And the distribution within the wear-resistant layer is uniform.This method has the advantages of high efficiency and low cost,and it is easy to realize automation.When the powder feeding gas flow rate is 4L/min,6L/min and8L/min,the volume fraction of WC particles in the wear-resistant layer are 20%,40%and 55%;respectively.When the powder feeding gas flow rate increases,the width of Fe₃W₃C transition layer at the edge of particles increases slightly and there are more blocky and fishbone Fe₃W₃C on the matrix,which is conducive to the combination of particles with the matrix and improves the hardness and wear resistance of the matrix.（7）The performance of the wear-resisting layer is closely related to the quantity,distribution and decomposition degree of WC particles in the wear-resisting layer.The wear-resisting layer prepared by laser cladding and plasma cladding has a high degree of WC decomposition.Consequently,the hardness distribution is more uniform and low,and the wear-resisting properties are poor.The heat source temperature of oxy-acetylene flame spray welding,oxy-acetylene flame surfacing,TIG surfacing and arc additive preparation method with synergistic powder and wire method is low,which will cause the low decomposition degree of WC.Among them,the wear-resisting layer prepared by arc additive preparation method with synergistic powder and wire（gas flow rate of powder delivery is 8L/min）and by oxyacetylene flame surfacing contain a large number of WC particles.There are multiple high hardness points with about 2500 HV in the hardness curve,which indicates that the wear-resisting layers prepared have excellent wear resistance.Compared with the wear-resisting layer prepared by traditional technology,the comprehensive performance of the wear-resisting layer prepared by arc additive preparation method with synergistic powder and wire is more excellent.It is more suitable for industrial production and agricultural application.