Laser cladding preparation method for improving wear resistance of cladding layer by doping tungsten carbide

Abstract

The invention discloses a laser cladding preparation method for improving the wear resistance of a cladding layer by doping tungsten carbide. According to the method, cladding process parameters are preliminarily obtained based on finite element heat flow analogue simulation, cladding layer preparation is carried out, cladding quality characterization is carried out to obtain the optimal cladding process parameters, and finally the cladding layer with the wear-resistant characteristic is obtained. The method comprises the following steps: firstly, constructing a heat flow coupling three-dimensional model, carrying out grid division, establishing a heat source model, defining thermophysical parameters of tungsten carbide (10-15%) nickel alloy composite powder and a matrix, and determining simulated boundary conditions; setting a multi-factor process parameter combination to carry out numerical simulation calculation, and determining laser processing process parameters of laser power, scanning speed and light spot diameter; preparing a cladding layer on the surface of the nodular cast iron by using tungsten carbide (10-15%) nickel alloy composite powder through a laser cladding method; and carrying out microscopic morphology and microhardness experiments to carry out quality analysis verification on the cladding layer, determining the optimal process parameters of laser power, scanning speed and light spot diameter when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and obtaining the laser cladding preparation method for improving the wear resistance of the cladding layer by doping tungsten carbide. The invention provides a new research method and a high-quality preparation approach for improving the wear resistance of the cladding layer by tungsten carbide, and can be widely applied to the fields of strengthening and repairing mining machinery, aerospace parts and the like.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of nickel alloy laser cladding layers, and particularly relates to a numerical simulation of a cladding layer doped with tungsten carbide (10% - 15%) particles to enhance the hard wear-resistant characteristics of nickel alloys and a preparation method based on laser cladding, microscopic morphology analysis, and microhardness characterization. Background Technique

[0002] Nickel-based alloys are widely used in various complex service fields such as aerospace (such as engine turbine blades), energy power (such as heat transfer tubes of nuclear power generators), and petrochemical industry (such as oil drill pipes) due to their good comprehensive properties such as friction and wear resistance, oxidation resistance, corrosion resistance, and self-fluxing properties. With the development of laser cladding technology and the increasing requirements for the hard wear-resistant characteristics of the surface of metal components in the service environment, traditional process control methods consume a large amount of manpower and material resources and still cannot effectively monitor the forming process of the cladding layer to obtain a high-quality cladding layer. At the same time, nickel alloy cladding layers have obvious deficiencies in terms of hardness and wear resistance, cannot meet the service performance requirements in multiple environments, and seriously limit their service life and application scope. By doping tungsten carbide particles (10% - 15%) and using the heat flow coupling numerical simulation technology, the surface hardness, wear resistance, and service life of the high-performance cladding layer can be significantly improved. Therefore, the simulation, preparation, and verification of the cladding layer doped with tungsten carbide particles (10% - 15%) to enhance the wear-resistant characteristics of nickel alloys have important application value and practical significance.

[0003] The nickel alloy wear-resistant cladding layer refers to the cladding surface with no obvious defects in the microscopic morphology and a microhardness higher than that of the raw material, which has important application value in the fields of high temperature and high pressure, hard wear resistance, and heavy load impact resistance. The forming process of the cladding layer involves the melting of the cladding powder and the substrate, the convective mass transfer in the molten pool, and the cooling and solidification of the cladding layer, accompanied by the generation and transfer of the temperature field and the flow field at all times. The transient forming characteristics cause a huge temperature gradient in the molten pool, which in turn leads to stress concentration in each region during the solidification process of the molten pool due to the differences in temperature distribution and the thermophysical properties of the mixed solutes, resulting in problems such as cracks, pores, and powder inclusions, leading to performance defects in the cladding layer. Laser power, scanning speed, and spot diameter are the main process parameters of laser cladding. Too low laser power will reduce the bonding strength between the cladding layer and the substrate, and too high laser power will cause over-melting of the cladding material and an increase in the dilution rate. The scanning speed is related to the existence time of the molten pool. When the scanning speed is too fast, the material cannot be completely melted, and when the scanning speed is too slow, a cladding layer with coarse grains is easily formed. If the spot diameter is too small, the energy density is too concentrated, and large internal stresses will appear in the cladding layer. If the spot diameter is too large, the energy density is too dispersed, and cracks are likely to appear in the cladding layer. The numerical simulation of the thermal-fluid coupling field is of great significance for the forming performance of the cladding layer, mainly because the simulation results can reveal the influence mechanism and regulation mechanism of laser process parameters on the evolution of the temperature gradient, the distribution of residual stress, and the flow of the molten pool. Laser power, scanning speed, and spot diameter are the key factors for regulating the forming mechanism of the cladding layer. Therefore, the preparation of high-performance cladding layers mainly involves optimizing the laser process parameters to deposit a composite strengthening cladding layer on the surface of low-performance substrates. With the rapid development of the field of materials science testing technology, microscopic morphology analysis and microhardness testing technology are widely used in the performance testing and verification of cladding layers due to their high precision, non-destructive nature, and wide applicability.

[0004] Patent 202010770493.2 discloses a tungsten carbide reinforced high-entropy alloy powder for laser cladding and a method for preparing a cladding layer. This method uses the tungsten carbide reinforced high-entropy alloy powder and laser cladding is carried out with process parameters of a laser power of 1.2 kW to 1.6 kW and a scanning speed of 150 mm / min to 300 mm / min to prepare the cladding layer. Good metallurgical bonding between the cladding layer and the substrate is achieved, and a cladding layer with high crack resistance, high temperature resistance, wear resistance, and corrosion resistance is obtained. However, the laser process parameters considered in this patent have limitations and are not conducive to the forming control of the cladding layer, and the process parameter range is set too wide, and the experimental method has disadvantages such as high cost and long cycle. Patent 202410101645.8 discloses a sequential coupling simulation method for laser cladding forming based on ANSYS. Aiming at the problems that existing laser cladding for repairing casting defects will cause large temperature gradients in the heat affected zone and the cladding zone and there are internal stresses, the influence of laser power and scanning speed on the temperature field and stress field of the cladding model is determined through full factor simulation experiments. By adjusting different process parameters, the influence laws of different parameters on nodes and molten pools can be deeply analyzed and compared, and reasonable process parameters are screened out. However, this method only conducts simulation analysis on laser power and scanning speed, the conditional variables are not set sufficiently, and only simulation experiments on the temperature field and stress field are carried out during the simulation process, lacking the simulation of the formation of solute convection in the molten pool, and there is still room for further optimization.

[0005] In summary, in the field of numerical simulation preparation of nickel alloy laser cladding, the existing laser cladding methods for improving the performance of nickel alloy with tungsten carbide have problems such as insufficient and inaccurate laser process parameters, and the experimental method has disadvantages such as high cost and long cycle. At the same time, in numerical simulation, the influence of the flow field movement of the molten pool on the preparation process is not considered. Therefore, the present invention provides a laser cladding preparation method for improving the wear resistance of nickel alloy cladding layer doped with tungsten carbide (10% - 15%) particles. 27 groups of process parameter combinations of 3 factors are designed. Through heat flow simulation, the influence mechanism and regulation mechanism of laser process parameters on the evolution of temperature gradient, residual stress distribution, and molten pool flow are revealed. The characteristic parameters of laser power, scanning speed, and spot diameter corresponding to when the cladding layer has no obvious crack, hole, powder inclusion defects and the hardness is higher than that of the raw material are determined. The hard and wear-resistant characteristics of the cladding layer are verified through microscopic morphology analysis and microhardness experiments, so as to realize the laser cladding preparation of improving the wear resistance of the cladding layer doped with tungsten carbide (10% - 15%) particles. The laser cladding preparation method of the present invention for improving the wear resistance of the cladding layer doped with tungsten carbide provides a new research method and high-quality preparation approach for improving the wear resistance of the cladding layer with tungsten carbide, and can be widely applied in fields such as the strengthening and repair of mining machinery and aerospace components, and has important application value. Summary of the Invention

[0006] The present invention discloses a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer. Based on finite element heat flow simulation, a three-dimensional heat flow coupling model is first constructed and meshed, a heat source model is established, and the thermal physical properties of tungsten carbide (10% - 15%) nickel alloy composite powder and the substrate are defined, and the simulation boundary conditions are established; a multi-factor process parameter combination is set, numerical simulation calculations are carried out, and the laser processing process parameters such as laser power, scanning speed, and spot diameter are determined; on the surface of ductile iron, a cladding layer is prepared by laser cladding using tungsten carbide (10% - 15%) nickel alloy composite powder; microtopography and microhardness experiments are carried out to analyze and characterize the quality of the cladding layer, and the characteristic parameters of laser power, scanning speed, and spot diameter are determined when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and a cladding layer with wear resistance is obtained. The technical solution adopted by the present invention is as follows: A laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer, characterized by including the following design steps: Step 1: Construct a three-dimensional heat flow coupling model for meshing, establish a laser heat source model, define the thermal physical properties of the cladding material, and establish the boundary conditions of the coupled field; set a multi-factor process parameter combination to carry out numerical simulation calculations, and based on the numerical simulation results, determine the laser processing process parameters such as laser power, scanning speed, and spot diameter; Step 2: Optimize the process parameters according to the numerical simulation, and use a nickel alloy composite powder doped with tungsten carbide particles (10% - 15%) to complete the preparation of the cladding layer on the surface of ductile iron through a laser cladding device; Step 3: Conduct microtopography analysis experiments to obtain the influence mechanism of laser process parameters on the defect morphology of the cladding layer; conduct microhardness experiments to obtain the microhardness control mechanism of laser process parameters at different positions along the melting depth direction of the sample; determine the optimal process parameters of laser power, scanning speed, and spot diameter when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and obtain a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer.

[0007] Step 1 specifically includes: (1) Use SolidWorks software to construct a three-dimensional multi-field coupling heat flow model, where the size of the substrate is set to 100 mm × 100 mm × 4 mm, and the size of the cladding layer is set to 40 mm × 8 mm × 1 mm, and import it into ANSYS Workbench and Flow 3D software; use tetrahedral adaptive meshing to mesh the cladding layer and the substrate, the minimum mesh size is set to 0.1 mm, and at the same time, the cladding layer is encrypted and meshed, and the total number of meshes is 111840; (2) Build a Gaussian surface moving heat source model, and compile the heat source model function through Mechanical APDL software and Visual Studio software, and then import them into ANSYS Workbench software and Flow 3D software respectively; With the help of JMat Pro software, calculate the various properties of the material, and define the thermal physical parameters of ductile iron QT450-10 and tungsten carbide particle (10% - 15%) nickel alloy composite powder, including thermal expansion coefficient, thermal conductivity, specific heat capacity, density, etc.; (3) Establish the boundary conditions of each field: The transient temperature field is heat transfer constrained by heat conduction, heat convection and thermal radiation, the stress field is constrained by the thermal stress formula, strain formula and yield formula, and the flow field is constrained by the enthalpy-porosity method melting and solidification model; (4) Take the laser power of 1000 W, 1500 W, 2000 W; scanning speeds of 5 mm / s, 10 mm / s, 15 mm / s; and spot diameters of 2 mm, 3 mm, 4 mm as control variables, set 27 groups of process parameter combinations with 3 factors and 3 levels, and carry out the coupled numerical simulation of the laser cladding temperature field, stress field and flow field; (5) Based on the results of the coupled heat flow numerical simulation, optimize the process parameter combinations with the melt pool temperature, residual stress in the melt pool, melt pool flow velocity information, etc. as the screening indicators, and obtain the laser processing process parameters of laser power, scanning speed and spot diameter.

[0008] Step 2 specifically includes: (1) Grind the surface of the ductile iron QT450-10 substrate to be flat to 2 μm - 3 μm, and clean and dry it with anhydrous ethanol; Place the nickel alloy composite powder doped with tungsten carbide particles (10% - 15%) in a drying oven, adjust the temperature to 100℃ - 120℃, and dry it for 4 h; (2) Set the pre-processing parameters of the laser, and use the coaxial powder feeding method through the laser cladding equipment to complete the preparation of the cladding layer on the surface of the ductile iron with the nickel alloy composite powder doped with tungsten carbide particles (10% - 15%).

[0009] Step 3 specifically includes: (1) Use a wire electrical discharge machining numerically controlled machine tool to cut the cladding layer into 10 mm×10 mm×3 mm block specimens, and polish the surface of the specimens with a polishing machine to make the surface roughness reach 0.4 μm - 0.8 μm; Place the polished specimens in anhydrous ethanol and ultrasonically clean them for 10 min. After cleaning, place them in a constant temperature oven, keep the temperature at 50℃ for 2 h to make the specimens completely dry; (2)Carry out microscopic morphology analysis experiments. Use a scanning electron microscope to observe the cladding layer. Set the instrument to low-resolution mode, select a magnification of 20 times, adjust the focusing position of the electron beam and calibrate the parameters to ensure the clarity and accuracy of the image; compare the microscopic morphology of the cladding layer cross-section with the numerically simulated molten pool morphology to characterize the authenticity and accuracy of the laser molten pool heat flow coupling numerical simulation; analyze the forming morphology of the microscopic cross-section, the distribution state of tungsten carbide, and defects such as cracks, pores, and powder inclusions. (3)Use a microhardness tester to measure the hardness of the cladding layer. The parameters are set as follows: load 200 g, holding time 15 s; measure the hardness value 3 times every 0.1 mm along the melting depth direction of the specimen and take the average value as the hardness value at this melting depth position until the measured hardness value tends to be stable and then stop the measurement. (4)Taking the microscopic defects morphology, dilution rate, and microhardness of the cladding layer as evaluation indicators, compare and analyze the influence mechanism of the evaluation indicators on the forming quality of the cladding layer; clarify the optimal process parameters of laser power, scanning speed, and spot diameter when the cladding layer has no obvious cracks, holes, and powder inclusion defects and the hardness is higher than that of the raw material, and obtain a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer.

[0010] The present invention discloses a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer. Based on finite element heat flow simulation, a laser cladding coupling geometric model is constructed to set the simulation environment. Taking laser power, scanning speed, and spot diameter as control variables, numerical simulation is carried out. The temperature, residual stress, and molten pool flow velocity information of the coupling field are screened for analysis and characterization, and the laser cladding process parameters are initially obtained; giving full play to the advantages of high precision, controllability, flexibility, and high efficiency of laser cladding to complete the preparation of the cladding layer, and using microscopic morphology and microhardness non-destructive high-precision experiments to analyze and verify the quality of the cladding layer. Clarify the optimal process parameters of laser power, scanning speed, and spot diameter when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and obtain a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer, which has important application value in the fields of mine machinery, strengthening and repairing of aerospace components, etc. Brief Description of the Drawings

[0011] Figure 1 Schematic diagram of the three-dimensional model of the numerical simulation temperature field and stress field of the present invention; Figure 2 Three-dimensional model diagram of the numerical simulation flow field of the present invention; Figure 3 Mesh division diagram of the numerical simulation three-dimensional model of the present invention; Figure 4 Numerical simulation process parameter diagram of the present invention; Figure 5 Test characterization process parameter diagram of the present invention; Figure 6 Cutting specimen diagram of the cladding layer of the present invention; Figure 7 Comparison diagram of the cross-sectional morphology of the SEM of the cladding layer of the present invention and the cross-sectional morphology of the numerical simulation; Figure 8 Data diagram of the dilution rate of the cladding layer of the present invention; Figure 9 Morphology diagram of the cladding layer of the present invention without obvious defects; Figure 10 Morphology diagram of obvious defects in the cladding layer of the present invention; Figure 11 Indentation morphology diagram of the microhardness of the present invention; Figure 12 Microhardness and hardness increase diagram of various parts of the present invention; Figure 13 Flow chart of numerical simulation and test characterization of the present invention. Detailed implementation manners

[0012] The following combines examples and drawings to make a detailed description of a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer of the present invention.

[0013] The present invention discloses a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer. Based on the finite element heat flow simulation, the cladding process parameters are initially obtained. First, a three-dimensional heat flow coupling model is constructed and meshed, a heat source model is established, and the thermal physical properties of tungsten carbide (10% - 15%) nickel alloy composite powder and the substrate are defined, and the simulation boundary conditions are established; a multi-factor process parameter combination is set to carry out numerical simulation calculations to clarify the laser power, scanning speed, and spot diameter laser processing process parameters; on the surface of ductile iron, a cladding layer is prepared by laser cladding using tungsten carbide (10% - 15%) nickel alloy composite powder; microtopography and microhardness experiments are carried out to analyze and verify the quality of the cladding layer, and the best process parameters of laser power, scanning speed, and spot diameter are determined when the cladding layer has no obvious defects and the hardness is higher than that of the raw material, and a cladding layer with improved wear resistance by doping tungsten carbide is obtained.

[0014] A laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer of the present invention specifically includes the following steps: 1. Construct a three-dimensional heat flow coupling model for meshing, establish a laser heat source model, define the thermal physical properties of the cladding material, and establish the boundary conditions of the coupling field; set a multi-factor process parameter combination to carry out numerical simulation calculations. Based on the numerical simulation results, clarify the laser power, scanning speed, and spot diameter laser processing process parameters, specifically including: (1) Use the Design Modeler module in ANSYS Workbench to construct a three-dimensional model of the multi-field coupling of heat flow. The size of the substrate is set to 100 mm × 100 mm × 4 mm, and the size of the cladding layer is set to 40 mm × 8 mm × 1 mm. Import them into ANSYS Workbench and Flow 3D software, as Figure 1 shown; use EDEM software to construct a powder bed geometry model and then import it into Flow-3D software. The size of the substrate is set to 100 mm × 30 mm × 10 mm, as Figure 2 shown; use tetrahedral adaptive meshing to mesh the cladding layer and the substrate. The minimum mesh size is set to 0.1 mm, and at the same time, the cladding layer is meshed more densely. The total number of meshes is 111,840, as Figure 3 shown; (2) Construct a Gaussian surface moving heat source model. Compile the heat source model function through Mechanical APDL software and Visual Studio software and import them into ANSYS Workbench software and Flow 3D software respectively; use JMat Pro software to calculate the various properties of the materials, and define the thermal physical parameters of ductile iron QT450-10 and tungsten carbide particle (10% - 15%) nickel alloy composite powder, including the coefficient of thermal expansion, thermal conductivity, specific heat capacity, density, etc.; (3) Establish the boundary conditions of each field: The transient temperature field is heat transfer constrained by heat conduction, heat convection and thermal radiation. The stress field is constrained by the thermal stress formula, strain formula and yield formula. The flow field is constrained by the enthalpy-porosity method melting and solidification model; (4) Set 27 groups of process parameter combinations with 3 factors and 3 levels by taking the laser power of 1000 W, 1500 W, 2000 W; the scanning speed of 5 mm / s, 10 mm / s, 15 mm / s; and the spot diameter of 2 mm, 3 mm, 4 mm as the control variables, and carry out the numerical simulation of the coupling of the laser cladding temperature field, stress field and flow field, as Figure 4 shown; (5) Based on the numerical simulation results of the heat flow coupling, optimize the process parameter combinations by taking the molten pool temperature, molten pool residual stress, molten pool flow velocity information, etc. as the screening indicators. Select the scanning speed of 10 mm / s, the spot diameter of 3 mm, and the laser powers of 1200 W, 1300 W, 1400 W, 1500 W for test research. At the same time, to characterize and verify the numerical simulation effect of this paper on the influence of different process parameters on the quality of the cladding layer, select the laser power of 1300 W, and select the scanning speeds of 5 mm / s and 15 mm / s, and the spot diameters of 2 mm and 4 mm respectively for comparison and verification, as Figure 5 shown.

[0015] 2. Optimize the process parameters according to numerical simulation. Use a laser cladding device to complete the preparation of the cladding layer on the surface of ductile iron with a nickel alloy composite powder doped with tungsten carbide particles (10% - 15%). Specifically, it includes: (1) Grind the surface of the ductile iron QT450 - 10 substrate flat to 2 μm - 3 μm, clean and dry it with anhydrous ethanol; Place the nickel alloy composite powder doped with tungsten carbide particles (10% - 15%) in an oven and adjust the temperature to 100°C - 120°C for drying treatment for 4 h; (2) Set the pre - processing parameters through a laser (LJ - RF - 6000W, Wuhan company, China), and use the co - axial powder feeding method to complete the preparation of the cladding layer on the surface of ductile iron with a nickel alloy composite powder doped with tungsten carbide particles (10% - 15%).

[0016] 3. Conduct microscopic morphology analysis experiments to obtain the influence mechanism of laser process parameters on the defect morphology of the cladding layer; Conduct micro - hardness experiments to obtain the micro - hardness control mechanism of laser process parameters at different positions along the melting depth direction of the sample; Determine the optimal process parameters of laser power, scanning speed, and spot diameter when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and obtain a laser cladding preparation method for doping tungsten carbide to improve the wear - resistant characteristics of the cladding layer. Specifically, it includes: (1) Use a wire - cut electrical discharge machine tool (DK7735, Suzhou company, China) to cut the cladding layer into 10mm×10 mm×3 mm block - shaped specimens, and polish the surface of the specimens with a polishing machine to make the surface roughness reach 0.4μm - 0.8 μm, as Figure 6 shown; Place the polished specimens in anhydrous ethanol and ultrasonically clean them for 10 min. After cleaning, place them in a constant - temperature oven at 50°C and keep them for 2 h to make the specimens completely dry; (2) Conduct microscopic morphology analysis experiments. Use a scanning electron microscope (SEM, SU 8600, Carl Zeiss AG, Germany) to observe the cladding layer. Set the instrument to the low - resolution mode, select a magnification of 20 times, adjust the focusing position of the electron beam and calibrate the parameters to ensure the clarity and accuracy of the image; Compare the cross - section microscopic morphology of the cladding layer with the free - surface molten pool obtained from the numerical simulation of the laser molten pool flow field, and find that the two are basically consistent, which characterizes the authenticity and accuracy of the numerical simulation of the laser molten pool heat - flow coupling; At the same time, based on this, the dilution rate of the cladding layer can be calculated. The formula for calculating the dilution rate of the cladding layer is: , where, A 1 is the area of the cladding layer, A 2 is the area of the metallurgical bonding layer, h is the layer height,H is the height of the clad layer; the degree of metallurgical bonding between the clad layer and the substrate can be characterized by the dilution rate. As Figure 7 shown, according to the dilution rate information of each sample, it can be known that the dilution rates of the remaining samples are all in the range of 10% - 15% except for samples 5, 7, and 8, which is a reasonable range of dilution rate. As Figure 8 shown; by comparing and analyzing the microscopic defect morphologies of the clad layer, the influence rules of the laser process parameter combinations on the defects of the laser clad layer such as cracks, pores, and powder inclusions are obtained. Among them, when the laser power of sample 3 is 1400 W, the scanning speed is 10 mm / s, and the spot diameter is 3 mm, there are no obvious defect morphologies in the clad layer except for individual pores. As Figure 9 shown; there are defects such as cracks, pores, and powder inclusions in varying degrees in the clad layers with other parameters. As Figure 10 shown; (3) Use a microhardness tester (HV - 100, Shenzhen company, China) to test the hardness of the clad layer. The parameters are set as: load 200 g, holding time 15 s; measure the hardness values 3 times every 0.1 mm along the melting depth direction of the specimen and take their average value as the hardness value at this melting depth position. As Figure 11 shown; analyze the changing trends of the hardness distributions of the substrate, heat - affected zone, and clad layer along the melting depth direction of each sample to obtain the influence rules of the laser process parameters on the microhardness. By calculating the average hardness value of the clad layer of each sample and the hardness improvement amplitude of the clad layer compared with the substrate, the hardness and improvement amplitude of the clad layers of samples 1 - 5 are relatively high. As Figure 12 shown; (4) Take the microscopic defect morphology, dilution rate, and microhardness of the clad layer as evaluation indicators to analyze the influence mechanism of the evaluation indicators on the forming quality of the clad layer; clarify that when there are no obvious cracks, holes, powder inclusion defects in the clad layer, the dilution rate is within a reasonable range, and the hardness is higher than that of the raw material and the improvement amplitude is relatively large, the optimal process parameters of laser power, scanning speed, and spot diameter are the laser power of 1400 W, scanning speed of 10 mm / s, and spot diameter of 3 mm of sample 3, and obtain a laser cladding preparation method for doping tungsten carbide to improve the wear - resistant characteristics of the clad layer.

[0017] In summary, the present invention provides a laser cladding preparation method for doping tungsten carbide to improve the wear - resistant characteristics of the clad layer, and the overall operation process is as Figure 13 shown. The present invention provides a new research method and a high - quality preparation approach for tungsten carbide to improve the wear - resistant characteristics of the clad layer, which can be widely applied in fields such as the strengthening and repair of mining machinery and aerospace components.

Claims

1. A laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer, characterized in that The design steps include: Step 1: construct a three-dimensional heat-flux coupling model for meshing, establish a laser heat source model and define the thermal physical parameters of the cladding material, and establish the boundary conditions of the coupling field; set a multi-factor process parameter combination to carry out numerical simulation calculations, and based on the numerical simulation results, clarify the laser processing process parameters of laser power, scanning speed, and spot diameter; Step 2, optimizing the process parameters according to numerical simulation, and using a laser cladding device to prepare a cladding layer on the surface of the ductile iron using a nickel alloy composite powder doped with tungsten carbide particles (10% to 15%); Step 3: Conduct microscopic morphology analysis experiments to obtain the influence mechanism of laser process parameters on the defect morphology of the cladding layer; conduct microhardness experiments to obtain the regulation mechanism of laser process parameters on the microhardness of the sample at different positions along the melting depth direction; clarify the optimal process parameters of laser power, scanning speed, and spot diameter when the cladding layer has no obvious defect morphology and the hardness is higher than that of the raw material, and obtain a laser cladding preparation method that dopes tungsten carbide to improve the wear resistance of the cladding layer.

2. The laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer according to claim 1 is characterized in that: Step 1 specifically includes: (1) A three-dimensional thermal-fluid multi-field coupling model was constructed using SolidWorks software, in which the size of the substrate was set to 100 mm × 100 mm × 4 mm, and the size of the cladding layer was set to 40 mm × 8 mm × 1 mm. The model was then imported into ANSYS Workbench and Flow 3D software. The cladding layer and the substrate were meshed using tetrahedral adaptive meshing, and the minimum mesh size was set to 0.1 mm. At the same time, the cladding layer was encrypted, and the total number of meshes was 111,840. (2) Construct a Gaussian surface moving heat source model, compile the heat source model function through Mechanical APDL software and Visual Studio software, and import it into ANSYS Workbench software and Flow 3D software respectively; use JMat Pro software to calculate the various properties of the material, and define the thermal physical properties of ductile iron QT450-10 and tungsten carbide particles (10%~15%) nickel alloy composite powder, including thermal expansion coefficient, thermal conductivity, specific heat capacity, density, etc.; (3) Establish the boundary conditions of each field: the transient temperature field is constrained by heat conduction, heat convection and heat radiation; the stress field is constrained by the thermal stress formula, strain formula and yield formula; the flow field is constrained by the enthalpy-pore method melting and solidification model; (4) With laser power of 1000 W, 1500 W, and 2000 W; scanning speed of 5 mm / s, 10 mm / s, and 15 mm / s; and spot diameter of 2 mm, 3 mm, and 4 mm as control variables, 3 factors and 3 levels were set to form a total of 27 sets of process parameter combinations, and numerical simulations of the coupled temperature field, stress field, and flow field of laser cladding were carried out; (5) Based on the results of thermal-fluid coupling numerical simulation, the process parameter combination is optimized using the molten pool temperature, molten pool residual stress, molten pool flow rate information, etc. as screening indicators to obtain the laser processing process parameters of laser power, scanning speed, and spot diameter.

3. The laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer according to claim 1, characterized in that: Step 2 specifically includes: (1) The surface of the ductile iron QT450-10 substrate was polished to 2 μm ~ 3 μm, cleaned with anhydrous ethanol and dried; the nickel alloy composite powder doped with tungsten carbide particles (10% ~ 15%) was placed in a drying oven adjusted to 100℃ ~ 120℃ and dried for 4 h; (2) The laser pre-processing parameters were set, and the cladding layer was prepared on the surface of ductile iron using a nickel alloy composite powder doped with tungsten carbide particles (10% to 15%) using a coaxial powder feeding method using a laser cladding equipment.

4. The laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer according to claim 1, characterized in that: Step 3 specifically includes: (1) The cladding layer was cut into 10 mm × 10 mm × 3 mm block samples using an EDM CNC wire cutting machine. The surface of the sample was polished using a polishing machine to make the surface roughness reach 0.4 μm ~ 0.8 μm. The polished sample was placed in anhydrous ethanol and ultrasonically cleaned for 10 min. After cleaning, it was placed in a constant temperature box at 50 °C for 2 h to completely dry the sample for experimental use. (2) Conduct microscopic morphology analysis experiments, use a scanning electron microscope to observe the cladding layer, set the instrument to low-resolution mode, select a magnification of 20 times, adjust the focus position of the electron beam and calibrate the parameters to ensure the clarity and accuracy of the image; compare the cross-sectional microscopic morphology of the cladding layer with the numerically simulated molten pool morphology to characterize the authenticity and accuracy of the numerical simulation of the laser molten pool thermal flux coupling; analyze the microscopic cross-sectional forming morphology, tungsten carbide distribution state, and defects such as cracks, pores, and powder inclusions; verify the authenticity and accuracy of the numerical simulation of the laser molten pool thermal flux coupling (3) The hardness of the cladding layer was tested using a microhardness tester with the following parameters: load 200 g, holding time 15 s; the hardness of the sample was measured three times along the direction of the penetration depth at intervals of 0.1 mm, and the average value was taken as the hardness value at the penetration depth position. The measurement was stopped until the hardness value obtained by the test became stable. (4) The microscopic defect morphology, dilution rate and microhardness of the cladding layer were used as evaluation indicators to compare and analyze the influence mechanism of the evaluation indicators on the forming quality of the cladding layer; the laser process parameters of laser power, scanning speed and spot diameter were determined when the cladding layer had no obvious defect morphology and its hardness was higher than that of the raw material, and a laser cladding preparation method for doping tungsten carbide to improve the wear resistance of the cladding layer was obtained.

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