Study On Microstructure And Properties Of Laser Cladding Cu-Ti-Ni Mixed Powder On Iron-carbon Alloy Surface

Cast iron and carbon steel are widely used as ferrocarbon alloys in industrial production.They have the advantages of low price,good casting performance,machinability,vibration damping,etc.,but in the use environment of complex stress,the material surface is prone to wear and deformation even broke.In this paper,laser cladding technology was used to prepare Cu-Ti-Ni composite powder on the surface of HT250 gray cast iron and T10 steel to prepare Cu-Ti-Ni composite coatings.X’Pert PRO PANalytical X-ray diffractometer,S-3400N scanning electron microscope,4XCJZ metallographic microscope,etc.were used to analyze the phase composition,microstructure,and composition distribution of the cladding structure and the evolution of Ti C in the structure was analyzed.The effects of laser processing parameters on the macro-morphology of the cladding layer were investigated.HXD-1000 TMSC/LCD microhardness tester and UMT-3 multifunctional friction and wear tester was used to test the hardness and friction and wear performance of the cladding layer.Under a single variable condition,with the laser power increases,the porosity and cracks of the gray cast iron cladding layer increased,and the morphology of the laser cladding layer on the surface of the two substrates showed irregular waves.Shape,the width of the cladding layer,the depth of the molten pool,and the dilution rate also increased.With the scanning speed decreasing,the heat absorption of the cladding layer increased per unit time,and the dilution rates of the two substrate cladding layers increased.With the preset coating thickness increases,and the coating absorbed more heat,and reduced the width,depth and dilution rate of the molten pool.When the preset coating thickness was 1.6 mm,the two laser cladding layers were relatively better formed.The cladding layer of HT250 gray cast iron was mainly composed ofα-Cu,Ti C,（Fe,Ni）and CFe15.1（γ-Fe austenite）.The diffraction peaks of T10 steel coating were mainly composed ofα-Fe（ferrite）,α-Cu,Ti C,（Fe,Ni）,and CFe15.1（γ-Fe austenite）.The Ti C reinforcing phase of the cladding layer was formed by the reaction between C atoms in the substrate and Ti atoms in the Cu-Ti-Ni mixed powder.The evolution process of the Ti C of the gray cast iron cladding layer was irregular unit cells,polyhedral particles,preferentially oriented dendritic Ti C,and finally secondary dendritic Ti C.The Ti C in the cladding layer of T10 steel was mostly uniformly distributed in the form of particles due to the low carbon content of the substrate.A single melt of the cladding layer structure and shielding gas may cause pores to appear in the cladding layer,and the residual stress caused by laser fusion causes cracks in the cladding layer.The microhardness of HT250 gray cast iron cladding layer is 350-750HV_0.2,and the microhardness of T10 steel cladding layer is 350-600HV_0.2,which are about 2 to 3 times that of their substrates.HT250 gray cast iron cladding layer has more complete and coarse Ti C particles,and its microhardness was generally higher than that of the T10 steel cladding layer,but the hardness of the heat affected zone of the T10 steel cladding layer was higher.Increasing the thickness of the preset coating can increase the hardness of the cladding layer,but the hardness of the cladding layer was not greatly affected by the laser process parameters.The wear resistance of the two iron-carbon alloy cladding layers were better than that of their substrates.The average friction coefficients of HT250 gray cast iron cladding layer and T10 steel cladding layer are 0.38 and 0.47,respectively,and the weight loss is less than the corresponding substrate.At room temperature,the wear surface of HT250 gray cast iron and T10 steel cladding layer both exhibits adhesive wear and abrasive wear,but the wear surface of T10 steel cladding layer was significantly oxidized and has better wear resistance.