Preparation And Properties Of Laser Cladding Iron-based Coating On Working Surface Of Ploughshare

As the key farming component of the plow,the plough share usually directly contacts with the soil and other abrasive particles under the condition of no lubrication.The working environment is bad and the service life is short,which seriously affects the farming efficiency and increases the farming cost.In this paper,based on previous studies,the performance and cost advantages of Fe based alloy cladding coating were integrated.The multi factor orthogonal regression experiment was used to improve the composition of Fe based alloy material.At the same time,the Fe based alloy coating was prepared on the surface of common plowshare steel 65Mn by using synchronous fractional laser.The preparation process,the coating properties and the coating properties were analyzed by combining simulation and experiment The laser parameters,cladding quality,microstructure and properties of the coating were analyzed.Based on ANSYS APDL parametric design language,the temperature field and thermal residual stress field of laser cladding Fe based alloy powder on 65Mn substrate were simulated and analyzed.The optimal process parameters of power and scanning speed were obtained as 1000W and 600mm/min.Based on the temperature field,the thermal residual stress of the coating is analyzed.The results show that the main compressive stress of the coating,the tensile stress of the substrate,and the thermal residual stress decrease from the middle to the surrounding,from the bottom of the cladding layer to the surface.With the increase of the coating thickness,the thermal residual stress of the coating also decreases.Based on ABAQUS simulation of ploughing process,the force and ploughing principle of plow were analyzed.The results showed that the maximum compressive stress of plow was3.569×10^-2MPa.When the cutting displacement increases from zero to 1200 N,the tillage resistance begins to fluctuate up and down.The stress of each part of the plough is different in the process of cultivation.Laser cladding can be used for local cladding according to the stress of the plough,which can not only improve the wear resistance of the plough,but also give consideration to the economy.The optimum material ratio of Fe based cladding coating is 4%Co,14%Ni and 15%Mo by orthogonal test and multi index comprehensive evaluation method,with coating surface hardness,friction coefficient and electrochemical corrosion rate as evaluation indexes.The microstructure,element distribution,phase structure,surface crack defects and mechanical properties of the coating were analyzed by scanning electron microscope(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD),Vickers microhardness tester,three-point bending tester and pendulum impact tester.It is found that there are no obvious cracks,pores and other defects on the surface of the laser cladding coating,and the bonding between the coating and the substrate is close,showing a good metallurgical bonding.Through comparative study of n No.1-No.9 group cladding coating and cladding coating with different Mo content on the basis of optimum material ratio,it is found that with the increase of Mo content,the formation of dendrite structure of coating can be promoted,and the dendrite also becomes finer.The cladding coating mainly contains Cr-Ni-Fe-C solid solution,Fe Cr solid solution,Cr₇C₃,Mo₂C and other intermetallic compounds?Phase,?The phase consists of Co₇Mo₆,Co Mo₂Ni and Cr₉Mo₂₁Ni₂.The microhardness of the coating is nearly 2times higher than that of the substrate,and the microhardness of the coating increases obviously with the increase of Mo element.Through three-point bending test,the bonding strength between Fe based cladding coating and 65Mn substrate is calculated to be 784.6 MPa,which quantitatively shows that the coating has high bonding strength.The hardness of the sample with Fe based cladding coating is greatly increased,while the impact toughness is slightly decreased,and Mo element can improve the toughness of the cladding coating to a certain extent.The abrasive wear test was carried out by MLD-10 dynamic load abrasive wear tester;The electrochemical characteristics of Fe based coating and substrate in soil corrosion were studied by electrochemical workstation chi604e;Ywx/q-150 salt spray corrosion test chamber was used to analyze the salt spray corrosion performance of the cladding coating.The results show that the impact abrasive wear resistance and erosion abrasive wear resistance of the coating are greatly improved;The corrosion current of the Fe cladding coating is two orders of magnitude smaller than that of the substrate,and the corrosion resistance of the alloy coating is significantly improved with the increase of Mo,Ni and Co content;In the salt spray corrosion experiment,the average corrosion rate of 65Mn steel is 24 mg·(dm2d)^-1,and the average corrosion rate of cladding coating is 0.53 mg·(dm2d)^-1.The wear resistance and corrosion resistance of the cladding coating are much better than that of 65Mn substrate,which can meet the application requirements.