A prediction and calculation method for the utilization rate of laser cladding powder

Abstract

The present invention belongs to the technical field of metal additive manufacturing, and relates to a prediction calculation method for the powder utilization rate of laser cladding, including: Step 1, establishment of a prediction model: A powder utilization rate prediction model is established using a second-order multiple regression equation; Step 2, calculation of the powder utilization rate based on the actual measured values of the coating geometric dimensions under different process parameters; Step 3, substituting the obtained multiple groups of process parameters and the calculated utilization rate into the established powder utilization rate prediction model to obtain the values of the coefficients in the powder utilization rate prediction model, and finally obtaining the powder utilization rate prediction model corresponding to different laser cladding process parameters; The present invention can quickly find the best matching point by predicting the powder utilization rate under different process parameters, select the optimal process parameters for cladding to improve its powder utilization rate; Therefore, the present invention can calculate the optimal process parameters, and under the conditions of these process parameters, it can effectively improve the effective utilization rate of the powder and reduce the processing cost of laser cladding.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and relates to a prediction calculation method for the powder utilization rate of laser cladding. Background Art

[0002] Laser Cladding is an advanced surface modification technology. By using a high-energy laser beam, metal powder or wire is melted synchronously with the surface of the substrate, and a dense coating with metallurgical bonding is formed after rapid solidification. This technology can prepare high-performance alloy layers on inexpensive substrates, significantly improving wear resistance, corrosion resistance, heat resistance and other properties, while achieving precise repair and remanufacturing. Laser Cladding has many core advantages such as high bonding strength, small heat influence, flexible materials, performance customization, green and efficient. Laser Cladding is used in the energy industry, mining machinery, petrochemical industry for equipment repair and remanufacturing, in transportation and die manufacturing for surface strengthening, and in nuclear power equipment and 3D printing for expansion in emerging fields. Therefore, laser cladding technology is widely used in a variety of industries and technical fields.

[0003] However, during the laser cladding process, a part of the powder is melted in the laser beam and metallurgically bonded with the substrate to form a coating, while another part of the powder is scattered outside the laser beam due to phenomena such as splashing and collision during the spraying process, resulting in powder loss, reducing the powder utilization efficiency. In severe cases, the powder utilization rate is even less than 50%. Process parameters used in laser cladding, such as powder feeding amount, laser power, scanning speed, etc., have a direct impact on the powder utilization rate. And the low powder utilization rate of laser cladding will cause a series of problems such as increased costs, reduced production efficiency, deteriorated process, and environmental impact.

[0004] Therefore, a device or method with low cost, high precision and high efficiency for improving the powder utilization rate of laser cladding is needed to solve the above technical problems. Summary of the Invention

[0005] The technical solution adopted by the present invention to solve the technical problem is: a prediction calculation method for the powder utilization rate of laser cladding, including the following steps:

[0006] Step 1, establishing a prediction model: establishing a powder utilization rate prediction model using a second-order multiple regression equation;

[0007] Step 2, calculating the measured utilization rate of the powder according to the actual measured values of the coating geometric dimensions under different process parameters;

[0008] Step 3, substituting the multiple groups of process parameters and measured utilization rates obtained in Step 2 into the powder utilization rate prediction model established in Step 1 to obtain the values of each coefficient in the powder utilization rate prediction model, and finally obtaining the powder utilization rate prediction model corresponding to different laser cladding process parameters.

[0009] Preferably, in the said step 1, the powder utilization rate prediction model is:

[0010]

[0011] Wherein, represents the predicted powder utilization rate, respectively represent each coefficient, P represents the laser power, V s represents the scanning speed, V f represents the powder feeding rate;

[0012] In step 2, the process parameters include: laser power, scanning speed, powder feeding rate.

[0013] Preferably, in the said step 2, the steps to obtain the actual measured powder utilization rate are:

[0014] Step 2-1, process parameter setting: Set the process parameters of laser cladding according to the orthogonal test design scheme;

[0015] Step 2-2, laser cladding: Clad a coating on the surface of the substrate according to the process parameters set in step 2-1;

[0016] Step 2-3, coating size detection: Detect the morphology and size of the coating clad in step 2-2. The contents of the morphology and size detection include: the width of the coating, the height of the coating;

[0017] Step 2-4, data recording: Record the process parameters in step 2-2 and the results of the morphology and size detection in step 2-3;

[0018] Step 2-5, calculate the actual measured powder utilization rate of the coating powder: Calculate the actual measured powder utilization rate of the coating according to the actual morphology of the coating, combined with the melting height and melting width of the coating.

[0019] More preferably, in the said step 2, single-layer and single-pass laser cladding is used for actual measurement.

[0020] More preferably, when the laser beam is a circular spot in the said step 2, the actual measured powder utilization rate is:

[0021] In the formula, represents the actual measured powder utilization rate, represents the density of the clad layer, S represents the travel of the laser beam, W represents the melting width of the coating, H represents the melting height of the coating, V s represents the scanning speed, Vf represents the powder feeding rate.

[0022] More preferably, when laser cladding is used to strengthen the surface of a non-magnetic metal part and the material of the part is 316L steel, the powder utilization rate prediction model is:

[0023]

[0024] In the formula, represents the predicted powder utilization rate, P represents the laser power.

[0025] Preferably, the powder utilization rate prediction model in step 1 is tested; the test methods include: comparing the predicted value and the experimental value of the regression equation, significance test of the regression equation, significance test of the regression coefficient, residual analysis, and experimental verification.

[0026] Preferably, in step 2, the spot shapes of the laser beams used include: circular spot, rectangular spot, annular spot, linear spot, and composite spot.

[0027] The beneficial effects of the present invention are:

[0028] 1. By establishing a prediction model between the powder utilization rate and process parameters, the present invention calculates the powder utilization rate under given laser cladding process parameters based on the powder utilization rate prediction model; by predicting the powder utilization rate under different process parameters, the best matching point can be quickly found, and the optimal process parameters can be selected for cladding to improve its powder utilization rate; therefore, the present invention can calculate the optimal process parameters, and under the conditions of these process parameters, the effective utilization rate of the powder can be effectively improved and the processing cost of laser cladding can be reduced.

[0029] 2. Predicting the powder utilization rate in advance by the present invention can also quantify the material consumption before implementing the cladding, more accurately plan the powder amount during procurement, reduce costs, and in addition, the present invention can evaluate the powder utilization rate under the new cladding process and verify the energy-saving effect of the new process through prediction; therefore, the present invention can not only save process costs and improve production efficiency, but also guide process optimization and technological innovation. Brief Description of the Drawings

[0030] Figure 1 is a schematic diagram for calculating the volume of a single-pass coating of a method for predicting and calculating the powder utilization rate of laser cladding according to the present invention;

[0031] Figure 2 is a schematic cross-sectional view of the straight part in the middle of the coating according to the present invention;

[0032] Figure 3 is a schematic diagram for calculating the volume of one end of a coating according to the present invention;

[0033] Figure 4 It is the microscopic observation diagram of the cross-section of the coating obtained from the orthogonal experiment of laser cladding of the present invention;

[0034] Figure 5 It is the residual normal probability distribution diagram of the powder utilization rate prediction model of the present invention;

[0035] Figure 6 It is the comparison diagram of the predicted value and the experimental value of the powder utilization rate prediction model of the present invention;

[0036] Figure 7 It is the schematic diagram of the steps of the prediction calculation method of the present invention.

[0037] In the figure, 1, substrate; 2, middle part of the coating; 3, end part of the coating. Specific embodiments

[0038] Next, the relevant technologies in the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Refer to Figures 1 to 7 As shown, the prediction calculation method of the laser cladding powder utilization rate in this embodiment includes the following steps:

[0040] S1. Process parameter setting: According to the orthogonal experiment design scheme, set the process parameters of laser power, scanning speed, and powder feeding rate;

[0041] S2. Laser cladding: Start the laser and clad single-track coatings with different process parameters on the surface of the substrate according to the designed process parameters;

[0042] S3. Coating size detection: After the cladding is completed, perform morphological size detection on the coating, including the detection of the width and height of the coating;

[0043] S4. Data recording: Record the parameters during the laser cladding process and the data of the detected coating morphological size for subsequent calculation of the coating volume.

[0044] S5. Establishment of the prediction coating model: Use a second-order multiple regression equation to establish a coating morphology prediction model, and test the regression model, including the comparison of the predicted value and the experimental value of the regression equation, the significance test of the regression equation, the significance test of the regression coefficient, residual analysis, and experimental verification.

[0045] S6. Calculate the powder utilization rate of the coating: According to the actual morphology of the coating, a calculation model for the molten mass of the powder in a single-pass clad layer was established, and the powder utilization rate of a single-pass coating was calculated in combination with the melt height and melt width of the coating.

[0046] In step S6, laser heating and melting is a very complex physical process. To establish a calculation model for the molten mass of the powder in a single-pass clad layer, the following assumptions were made: (1) The cross-sectional profile of a single-pass coating is regarded as a part of a circle, as Figure 2 shown. (2) The end profile of a single-pass coating is regarded as a part of a sphere, as Figure 2 shown. (3) The physical properties of the powder and the substrate material are constant.

[0047] The measured utilization rate of the powder is expressed as:

[0048]

[0049] where m is the coating mass, M is the mass of the powder output by the powder feeder during the time of a single-pass clad layer by laser cladding.

[0050] When preparing a single-pass clad layer by laser cladding, let the action time of the laser be t , and the expression of time t is:

[0051]

[0052] where S is the travel distance of the laser beam, V S is the laser scanning speed.

[0053] The mass of the powder output by the powder feeder during the time of a single-pass clad layer by laser cladding M , can be expressed by the product of the powder feeding rate V f and the laser action time t :

[0054]

[0055] The coating mass m is expressed as:

[0056]

[0057] In the formula, is the coating density, V is the coating volume.

[0058] Since the laser beam used in this embodiment is a circular spot, the actual morphology of the coating is as shown schematically Figure 1As shown. Then the volume of the coating V is expressed as:

[0059]

[0060] where V 2 is Figure 1 the volume of the middle straight part of the middle coating, V 3 is Figure 1 the volume of one end part of the middle coating.

[0061] The cross-sectional schematic diagram of the middle straight part of the coating is as shown in Figure 2 which, the cross-section of the middle part 2 of the coating on the substrate 1 is a circular segment, and the radius of the circular segment is R and the central angle corresponding to the circular arc of the circular segment is θ , W is the weld width, H is the weld height.

[0062] The length L of the middle straight part of the coating is the travel S of the laser beam minus the lengths of the two end parts in the direction of the laser beam movement. Then the length of the middle straight part of the coating 2 can be expressed as:

[0063]

[0064] Then the volume V 2 of the middle straight part of the coating can be expressed as:

[0065]

[0066] The coating end 3 is as shown in Figure 3 which, in the coating end 3, W is the weld width, H is the weld height.

[0067] Then the volume V 3 of one coating end 3 is expressed as:

[0068]

[0069] The volume V of the coating is expressed as:

[0070]

[0071] where, the angle θ of the circular segment part occupying the complete sector can be further expressed as:

[0072]

[0073] The radius RIt can be further expressed as:

[0074]

[0075] Actual powder utilization rate is:

[0076]

[0077] In step S5, the establishment of the prediction coating model includes establishing and predicting the powder utilization rate of the coating through a second-order multiple regression equation. During the laser cladding process, the form of the multiple regression model of the coating powder utilization rate is:

[0078]

[0079] where is the regression equation, n represents the number of input values, represents the i th input value, are the regression coefficients of each item, e is the residual term.

[0080] Set the height of the laser cladding coating to H , and the width of the cladding to W , with the laser power P , scanning speed V s , and powder feeding rate V f as input factors, and the laser cladding powder utilization rate as the output response, to establish a powder utilization rate prediction model:

[0081]

[0082] where represents the coefficients, represents the predicted value of the powder utilization rate.

[0083] Example

[0084] In this example, the surface of a non-magnetic metal part is strengthened, and the material of this part is 316L steel.

[0085] Process parameter setting: The protective gas and powder feeding gas are both high-purity argon. The flow rate of the protective gas is 20 L / min, the flow rate of the powder feeding gas is 6 L / min, and the spot diameter is fixed at 3 mm.

[0086] Laser Cladding: The substrate is 316L stainless steel with dimensions of 200mm×100mm×10mm. Before the test, the surface of the substrate was thoroughly polished with 60-mesh sandpaper to remove surface oxides, making the substrate surface flat and smooth. Then, the substrate surface was cleaned to remove defects such as oil stains and impurity particles on the substrate surface. The cladding powder is nickel-based superalloy powder.

[0087] An orthogonal test table was used to design the test scheme, and 16 groups of test parameters were obtained. The laser was started, and 16 coatings under different process parameters were cladded on the surface of the substrate according to the designed process parameters.

[0088] Coating Dimension Detection: After the cladding was completed, the prepared coating was cut using a wire electrical discharge machine, and the cross-section of the coating was polished until the surface was flat and smooth. An optical electron microscope was used to measure the width and height of the coating, as Figure 4 shown.

[0089] Data Recording: Record the data of each group of laser cladding process parameters and the corresponding coating morphology dimensions obtained.

[0090] Calculate the actual measured powder utilization rate of the coating: According to the actual morphology dimensions of the coating, calculate the actual measured powder utilization rate of each coating:

[0091] The dimensions of the 16 coatings under different laser cladding process parameters obtained from the orthogonal test and the calculated actual measured powder utilization rates are shown in Table 1.

[0092] Table 1

[0093] In Table 1, P is the laser power (W), V s is the scanning speed (mm / s), V f is the powder feeding rate (r / min), H is the melting height (mm), W is the melting width (mm), is the actual measured utilization rate of the powder.

[0094] Establishment of the Powder Utilization Prediction Model: Substitute the test data in Table 1 into the coating powder utilization prediction model formula, and calculate the equation coefficients through calculation. The results are as follows:

[0095]

[0096] The regression model is tested, including the significance test of the regression coefficients of the regression equation, the goodness-of-fit test, the residual analysis, and the comparison between the predicted values and the experimental values, and experimental verification is carried out. The significance test of the prediction model obtains a P-value of 0.0032, which is much smaller than 0.05, indicating that the model is significant. The regression determination coefficient value of the prediction model is 0.9784, which is close to 1, indicating that the goodness-of-fit of the prediction model is good.

[0097] Figure 5 is the residual normal probability distribution diagram of the powder utilization rate prediction model. It can be seen that the residual normal probabilities are all randomly distributed near the straight line, indicating that the equation has a good fit for the random error and good adaptability. Figure 6 is the comparison diagram between the predicted values and the experimental values of the powder utilization rate obtained by using the prediction model. All points in the figure are distributed near the straight line, indicating that the results predicted by the model are in high agreement with the experimental results and have good consistency.

[0098] To further verify the accuracy of the powder utilization rate prediction model, three groups of laser power, scanning speed, and powder feeding rate different from those in Table 1 are arbitrarily selected as the laser cladding process parameters. First, use the powder utilization rate prediction model to make predictions and obtain the predicted values of the powder utilization rate under the three groups of process parameters. Then, carry out single-layer single-pass laser cladding experiments for actual measurement to obtain the experimental values of the powder utilization rate under the three groups of process parameters. Finally, calculate the relative error between the predicted values and the experimental values. The prediction and experimental data are shown in Table 2.

[0099] Table 2

[0100] In Table 2, P is the laser power (W), V s is the scanning speed (mm / s), V f is the powder feeding rate (r / min).

[0101] It can be seen from Table 2 that the maximum relative error of the powder utilization rate prediction in the three groups of data is 5.3%, and the minimum relative error is 4.0%, which proves the accuracy of the prediction model.

[0102] Therefore, based on the prediction of the powder utilization rate, in this embodiment, when selecting the laser cladding process parameters, the consideration of the powder utilization rate can be added, and the process parameters with higher utilization rate can be selected for implementation to reduce the waste of laser cladding costs, thereby controlling production costs, improving production efficiency, and ensuring production processes.

[0103] In summary, the present invention establishes a prediction model between powder utilization rate and process parameters, calculates the measured powder utilization rate under given laser cladding process parameters based on the powder utilization rate prediction model; by predicting the measured powder utilization rate under different process parameters, quickly finds the best matching point, selects the optimal process parameters for cladding to improve its powder utilization rate; therefore, the present invention can calculate the optimal process parameters, under which the effective powder utilization rate can be effectively improved and the processing cost of laser cladding can be reduced.

[0104] It should be emphasized that the above are only the preferred embodiments of the present invention, and do not constitute any form of limitation to the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A prediction and calculation method for the utilization rate of laser cladding powder, characterized in that It includes the following steps: Step 1, prediction model establishment: Establish a powder utilization rate prediction model using a second-order multiple regression equation; Step 2, calculate the measured powder utilization rate based on the actual measured values of the coating geometric dimensions under different process parameters; Step 3, substitute the multiple groups of process parameters and measured utilization rates obtained in Step 2 into the powder utilization rate prediction model established in Step 1 to obtain the values of each coefficient in the powder utilization rate prediction model, and finally obtain the powder utilization rate prediction model corresponding to different laser cladding process parameters; In Step 1, the powder utilization rate prediction model is: ； Among them, represents the predicted powder utilization rate, respectively represent the coefficients, P represents the laser power, V s represents the scanning speed, V f represents the powder feeding rate; In Step 2, the process parameters include: laser power, scanning speed, powder feeding rate; In Step 2, the steps to obtain the measured powder utilization rate are: Step 2-1, process parameter setting: Set the process parameters of laser cladding according to the orthogonal test design scheme; Step 2-2, laser cladding: Clad a coating on the substrate surface according to the process parameters set in Step 2-1; Step 2-3, coating dimension detection: Detect the morphology and dimension of the coating clad in Step 2-2, and the content of the morphology and dimension detection includes: the width of the coating, the height of the coating; Step 2-4, data recording: Record the process parameters in Step 2-2 and the results of the morphology and dimension detection in Step 2-3; Step 2-5, calculate the measured powder utilization rate of the coating powder: Calculate the measured powder utilization rate of the coating according to the actual morphology of the coating, combined with the melting height and melting width of the coating; In Step 2, when the laser beam is a circular spot, the calculation formula for the measured powder utilization rate is: ； In the formula, represents the measured utilization rate of the powder, represents the density of the cladding layer, S represents the travel of the laser beam, W represents the width of the coating melt, H represents the height of the coating melt, V s represents the scanning speed, V f represents the powder feeding rate.

2. The prediction calculation method of the utilization rate of laser cladding powder according to claim 1, wherein In Step 2, single-layer single-pass laser cladding is used for actual measurement.

3. A prediction and calculation method for the utilization rate of laser cladding powder according to claim 1, characterized in that, When laser cladding is used to strengthen the surface of a non-magnetic metal part and the part material is 316L steel, the powder utilization rate prediction model is: ； In the formula, represents the predicted powder utilization rate, P represents the laser power.

4. The prediction calculation method of the utilization rate of laser cladding powder according to claim 1, characterized in that, Verify the powder utilization rate prediction model in Step 1; The verification methods include: comparison of the predicted value and experimental value of the regression equation, significance test of the regression equation, significance test of the regression coefficient, residual analysis, and experimental verification.

5. A prediction calculation method for the utilization rate of laser cladding powder according to claim 1, characterized in that In Step 2, the spot shapes of the laser beams used include: circular spot, rectangular spot, annular spot, linear spot, composite spot.

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