Laser cladding repair method

Abstract

The invention discloses a laser cladding repairing method which comprises the steps that laser cladding powder is prepared, a to-be-repaired part is subjected to laser cladding, a cladding layer is obtained, and the toughness of the cladding layer is 1.1-1.3 times that of the to-be-repaired part; the tensile strength of the laser cladding powder meets the requirement for the tensile strength of the to-be-repaired part, the elastic modulus of the laser cladding powder is 0.9-1.1 times of the elastic modulus of the to-be-repaired part, and the thermal expansion coefficient of the laser cladding powder is 0.9-1.1 times of the thermal expansion coefficient of the to-be-repaired part. And the yield strength of the laser cladding powder is 0.9-1.1 times of the stress of the to-be-repaired component. According to the method, the design benchmarking of the repaired part is added, and the repair standard of the repaired workpiece, the selection of the laser cladding powder and the laser cladding process parameters are confirmed by means of simulation calculation, test piece verification and the like, so that the repaired part meets the use requirement, and the cracking tendency of cold and hot cracks is avoided.

Description

Technical Field

[0001] The invention relates to the field of laser cladding, and in particular to a laser cladding repair method. Background Art

[0002] Remanufacturing technology is an advanced form of recycling. It is not only an extension of the manufacturing industry, but also one of the main ways to achieve energy conservation and emission reduction, sustainable development and advanced manufacturing.

[0003] The motor end cover is prone to friction, wear, corrosion and fatigue failure during service, which seriously affects the normal operation of the motor. At present, the motor end cover bearing chamber wear is generally scrapped.

[0004] Laser cladding technology is a commonly used remanufacturing technology. It uses high-energy-density lasers to irradiate the workpiece surface. By adding appropriate cladding materials, it melts together with a thin layer on the workpiece substrate surface, and quickly solidifies to form a surface coating with extremely low dilution and metallurgical bonding with the substrate material. This significantly changes the wear resistance, corrosion resistance, heat resistance, and oxidation resistance of the workpiece surface while restoring the geometric dimensions of the workpiece. The cladding layer is metallurgically bonded to the substrate, has little thermal impact, high processing efficiency, and simple and convenient post-processing, making it suitable for remanufacturing research on motor shafts and end covers.

[0005] At present, when the bearing chamber of the end cover of the motor is found to be worn, it is generally scrapped. In the prior art, some conventional repair methods are used after the end cover bearing chamber is worn, but the surface wear resistance and corrosion resistance are poor, which cannot meet the use requirements, and it is difficult to serve for a long time after restoration.

[0006] In the prior art, the invention patent application with publication number CN102031519A discloses a laser cladding repair process for a circular shear blade, including: step 1: material preparation: preparing repair alloy powder and strengthening alloy powder; step 2: shear blade surface pretreatment: step 2.1) cleaning the shear blade surface; step 2.2) drying the shear blade surface; step 3: laser cladding repair layer: using the repair alloy powder, laser cladding the repair area to form the repair layer; step 4: machining strengthening area: machining the strengthening area on the shear blade surface and / or the repair area; step 5: laser cladding strengthening layer: using the strengthening alloy powder, laser cladding the strengthening area to form the strengthening layer. Without post-repair inspection, it is impossible to confirm that the repaired strengthening layer meets the workpiece use requirements. This scheme adopts laser cladding to repair the worn centrifugal fan bearing seat, but does not explain the cladding material selection and evaluation criteria for laser repair of the bearing seat and the selection of laser cladding process parameters.

[0007] The invention patent application with application number CN107414249B discloses a surfacing welding repair method for the bearing chamber of the motor end cover, which uses surfacing welding to repair the bearing chamber of the motor end cover. This solution uses surfacing welding to repair the motor end cover, but the heat affected zone of the surfacing welding is large and the deformation of the workpiece is large.

[0008] In summary, it can be seen that in the prior art, directly replacing the worn end cover of the motor is very costly, and repairing the end cover by surfacing welding or other methods cannot meet the requirements for the use of the end cover. Summary of the invention

[0009] The present invention aims to provide a laser cladding repair method, so that the repaired parts can meet the use requirements and avoid the cracking tendency of hot and cold cracks.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A laser cladding repair method, comprising preparing laser cladding powder, laser cladding a part to be repaired, and obtaining a cladding layer, wherein the toughness of the cladding layer is 1.1 to 1.3 times that of the part to be repaired;

[0012] The tensile strength of the laser cladding powder meets the tensile strength requirement of the part to be repaired, the elastic modulus of the laser cladding powder is 0.9 to 1.1 times the elastic modulus of the part to be repaired, the thermal expansion coefficient of the laser cladding powder is 0.9 to 1.1 times the thermal expansion coefficient of the part to be repaired, and the yield strength of the laser cladding powder is 0.9 to 1.1 times the stress of the part to be repaired.

[0013] While restoring the geometric dimensions of the component to be repaired, a cladding layer with toughness superior to that of the substrate is designed to allow the welding stress to be transmitted to the cladding layer, avoiding the tendency of cold and hot cracks.

[0014] According to the embodiments of the present invention, the present invention can be further optimized. The following is the technical solution formed after optimization:

[0015] The parts to be repaired include motor end covers or motor support parts. These parts may fail to meet the size requirements due to friction, vibration, corrosion and other factors during use.

[0016] In one of the preferred embodiments, the component to be repaired is a motor end cover, and the yield strength of the laser cladding powder is 0.9 to 1.1 times the stress at the bearing chamber of the motor end cover.

[0017] In one of the preferred embodiments, the laser cladding powder includes the following components in weight percentage: C 0.25%-0.35%, Mn 0.35-0.45%, Si 0.2%-0.4%, Cr 2%-4%, Mo 0.1%-0.5%, Ni 3-8%, and the balance is Fe.

[0018] In one of the preferred embodiments, the laser cladding powder includes the following components in weight percentage: C 0.25%-0.3%, Mn 0.4-0.45%, Si 0.2%-0.3%, Cr 3%-4%, Mo 0.3%-0.5%, Ni 3-6%, and the balance is Fe.

[0019] In one of the preferred embodiments, the process parameters of the laser cladding are: laser power 1900-2100 W, scanning speed 5-7 mm / s, powder feeding rate 4-6 g / min, spot size 2.5-7 mm, and shielding gas is argon.

[0020] In one of the preferred embodiments, the process parameters of the laser cladding are: laser power 1900-2000W, scanning speed 5-6mm / s, powder feeding amount 4-5g / min, spot size 5-7mm, and shielding gas is argon.

[0021] Laser cladding process parameters include laser power, scanning speed, powder feeding rate, offset, spot size, etc. Among them, laser power, scanning speed and spot diameter play a key role in the quality of the cladding layer. If the laser power is too large, the powder will melt quickly, some elements will be vaporized, the coating composition will be uneven, and defects will occur; if the laser power is too small, some powders will not be melted in time.

[0022] If the scanning speed is low, the laser action time will increase relatively, and there will be enough time for heat exchange and gas overflow with the substrate, and the density of the coating will be improved; if the scanning speed is too low, there will be too much local liquid phase and residue, and the flatness will deteriorate as the scanning speed decreases. The size of the spot is inversely correlated with the laser energy density - if the spot is small and the laser energy density is high, the energy is concentrated and the melting intensity is high, but its production capacity and efficiency are relatively reduced; on the contrary, if the spot is large, the energy density is low, the energy intensity is weak, the melting intensity is weak, and the melting reaction is not strong. When the spot is deformed, if it appears in an elliptical shape, it will have an adverse effect on the effect of the laser cladding experiment. Therefore, in order to ensure the normal operation of the cladding, the spot diameter should be kept within the range of 2.5-7mm, and the shielding gas is argon.

[0023] In one of the preferred embodiments, laser cladding adopts synchronous powder feeding, which can be divided into preset powder feeding and synchronous powder feeding according to different powder feeding methods. Preset powder feeding is to pre-cover the alloy powder material to be clad on the surface of the substrate, and then use the laser beam to scan the surface of the alloy pre-cladding layer. Synchronous powder feeding is to use a special conveyor to directly deliver the alloy powder into the laser action area. Before the powder reaches the melting zone, it passes through the light beam and is heated to a red-hot state. After falling into the melting zone, it melts immediately and is fed in with the substrate and powder to form an alloy cladding layer. Compared with preset powder feeding, synchronous powder feeding has a complex structure, high powder utilization rate, and the powder is preheated, so the cladding quality is good and the versatility is strong.

[0024] In one preferred embodiment, the laser cladding further includes the following steps:

[0025] A. Clean the parts to be repaired, measure the dimensions, and determine the worn parts and amount of wear;

[0026] B. Perform flaw detection on the parts to be repaired after cleaning in A to facilitate failure analysis and life analysis;

[0027] C. According to the wear amount of the parts to be repaired in A, remove the fatigue layer by 0.5-1mm.

[0028] If the fatigue layer is removed too shallowly, it will affect the bonding quality between the cladding layer and the substrate. If it is removed too deeply, it will cause a waste of laser cladding resources. After the fatigue layer is removed, it is cleaned and used as the processing surface for laser cladding.

[0029] In one preferred embodiment, the laser cladding further includes the following steps:

[0030] After completing the laser cladding of the repaired part, the end cap is machined according to the required size of the repaired part, and the size requirements of the drawing are met, including roughness and dimensional tolerance.

[0031] Carry out dimensional inspection on the parts to be repaired after processing;

[0032] After the dimensional inspection is completed and qualified, the parts to be repaired are subjected to penetrant testing to confirm that there are no cracks on the surface.

[0033] The method of the present invention is mainly based on the laser cladding technology to repair the worn end cover of the motor. By benchmarking the technical requirements of the motor end cover, the stress condition of the end cover is analyzed by simulation. By matching the mechanical properties, elastic modulus and other parameters of the end cover material, suitable laser cladding powder, laser equipment and cladding process parameters are selected, and the selected laser cladding process parameters are verified by metallographic tests, tensile tests and shear tests to confirm that the repaired motor end cover meets the technical use requirements.

[0034] The present invention includes the following key points:

[0035] 1. The present invention is applied to the repair of the out-of-tolerance size of the bearing chamber of the motor end cover;

[0036] 2. The product in this method is the motor end cover, which can be extended to motor support components such as the shaft;

[0037] 3. The present invention does not impose a rigid regulation on the size tolerance of the motor end cover bearing chamber, which can be from a few μ to several hundred μ;

[0038] 4. The present invention does not make any rigid regulations on the selection of laser equipment. As long as the laser head can meet the repair requirements of the end cover bearing chamber, it can be either side-axis powder feeding or coaxial powder feeding;

[0039] 5. The qualified index for end cover repair in the present invention is determined by simulating the actual operating conditions through simulation analysis;

[0040] 6. The present invention utilizes laser cladding technology for repair. By comparing the mechanical properties and material characteristics of the end cap, suitable laser cladding powder is selected. A similar method can also be used to select powder for subsequent repair of motor support components such as end caps made of other materials;

[0041] 7. The present invention uses test pieces for verification, and performs metallographic testing, tensile testing, and shear testing on the test pieces to select and confirm the laser cladding powder;

[0042] 8. After the laser cladding powder is confirmed in the present invention, appropriate laser cladding process parameters are selected and confirmed by using orthogonal test;

[0043] 9. After the physical object is repaired and qualified in the present invention, a penetrant flaw detection is used to confirm that there are no cracks in the end cover after the repair. Other flaw detection means such as ultrasonic waves can also be used for detection.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. The method of the present invention enables the repaired parts to meet the use requirements and avoid the cracking tendency of hot and cold cracks;

[0046] 2. The theoretical basis of the present invention is mature and sufficient, and has been proven to be effective and reliable through long-term practice;

[0047] 3. The implementation of the present invention can repair the quality problem of the motor end cover bearing chamber size out of tolerance, effectively reducing the maintenance cost;

[0048] 4. The implementation of the present invention will not damage the quality of other components on the surface of the motor end cover; BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of a repair method in one embodiment of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0051] The specific implementation steps are as follows:

[0052] 1. Theoretical analysis: According to the technical indicators of the motor end cover, the mechanical indicators of the motor end cover (made of ductile iron) are tensile strength Rm≥400Mpa; the elastic modulus of the end cover is 169Gpa. Therefore, the laser cladding powder must meet the mechanical strength of the end cover: tensile strength Rm≥400Mpa; the elastic modulus and thermal expansion coefficient of the material should be as close as possible to the end cover to reduce the probability of cracks during the laser cladding process. The stress at the end cover bearing chamber is analyzed by simulation, which is used as the yield strength indicator after the end cover bearing chamber is repaired.

[0053] Ductile iron has poor welding performance and is brittle. It is prone to cold cracks and hot cracks during cladding. It also has poor corrosion resistance and temperature resistance. Iron-based nickel-chromium alloy powder can be used as cladding powder to restore the geometric dimensions of the end cover while designing a cladding layer that is superior to the toughness of the substrate, allowing the welding stress to be transmitted to the cladding layer to avoid the cracking tendency of cold and hot cracks. Four types of powders, 316, 625, 4169, and sd1, were initially selected for laser cladding on the ductile cast iron substrate, and the test pieces were cut for metallographic testing. It was found that the samples laser clad with 4169, 316, and sd1 powders had slight cracks. Finally, the elastic modulus of 625 powder and ductile cast iron end cover material were compared, and it was found that the elastic modulus was close. Through the above theoretical and experimental analysis, the appropriate laser cladding powder was finally selected. The composition and weight percentage content of the cladding powder are: C0.27\Mn0.42\Si0.3\Cr3.74\Mo0.36\Ni5.6\Fe balance.

[0054] Laser cladding process parameters include laser power, scanning speed, powder feeding rate, offset, spot size, etc. Among them, laser power, scanning speed and spot diameter play a key role in the quality of the cladding layer. If the laser power is too large, the powder will melt quickly, some elements will be vaporized, the coating composition will be uneven, and defects will occur; if the laser power is too small, some powders will not be melted in time.

[0055] After selecting the laser cladding powder in step 1, the process parameters are selected according to the orthogonal test to carry out laser cladding of the specimen, and the metallographic structure and properties of the cladding layer of the clad specimen are characterized to select and determine the appropriate process parameters.

[0056]

[0057]

[0058] Finally, the optimal laser power was determined to be 2000W, scanning speed 5mm / s, powder feeding amount 5g / min, and spot size 5mm.

[0059] 2. Carry out metallographic inspection, tensile test and shear test on the specimen after cladding according to national standards to confirm that the cladding layer of the specimen after laser cladding is well bonded to the substrate, and the mechanical performance indicators and bonding strength meet the requirements in step 1.

[0060] Embodiment 1:

[0061] The first step is preparation before repair: clean the motor end cover No. 1, measure the bearing chamber size to determine the amount of wear, and perform flaw detection on the end cover bearing to assess its repairability and develop a repair process. According to the amount of wear on the end cover, remove 0.5mm of the surface fatigue layer on one side as the processing surface.

[0062] The second step of the repair process: The material of the end cover is ductile cast iron. According to the material configuration of the end cover, the metal alloy powder No. 1 required for laser cladding is determined, and its powder composition is C0.27\Mn0.42\Si0.3\Cr3.74\Mo0.36\Ni5.6\Fe remainder. The end cover is installed on the fixture, the laser equipment is debugged, and the process parameters of laser cladding are set: laser power 2000W, scanning speed 5mm / s, powder feeding amount 5g / min, spot size 5mm, and protective gas is argon. The end cover bearing chamber is laser clad using synchronous powder feeding, and the cladding layer thickness is 1mm.

[0063] The third step is machining after cladding: Use electronic measuring tools (accuracy 0.001mm) on the grinder to measure the diameter edge size of the end cover bearing chamber and restore it. The restored size is best in the center of the tolerance zone.

[0064] The fourth step is post-cladding inspection: Perform penetrant testing on the repaired end cover to confirm that there are no cracks.

[0065] Comparative Example 1:

[0066] The first step is preparation before repair: clean the motor end cover No. 2, measure the bearing chamber size to determine the amount of wear, and perform flaw detection on the end cover bearing to assess its repairability and develop a repair process. According to the amount of wear on the end cover, remove 0.5mm of the surface fatigue layer on one side as the processing surface.

[0067] The second step of the repair process: According to the material configuration of the end cap, the metal alloy powder No. 2 required for laser cladding is selected, and its powder composition is

[0068] P≤0.035\S≤0.03\Ni:010.0-14.0\Cr:16.0-18.5\Mo:2.0-3.0\Fe remainder. Install the end cap on the fixture, debug the laser equipment, and set the laser cladding process parameters: laser power 2000W, scanning speed 5mm / s, powder feeding 5g / min, spot size 5mm, and protective gas is argon. Use synchronous powder feeding to laser clad the end cap bearing chamber, and the cladding layer thickness is 1mm.

[0069] The third step is machining after cladding: Use electronic measuring tools (accuracy 0.001mm) on the grinder to measure the diameter edge size of the end cover bearing chamber and restore it. The restored size is best in the center of the tolerance zone.

[0070] The fourth step is post-cladding inspection: The repaired end cover is subjected to penetrant testing and cracks are found.

[0071] The difference between this comparative example and Example 1 is that the powder for laser cladding is adjusted.

[0072] Comparative Example 2:

[0073] The first step is preparation before repair: clean the motor end cover of No. 3, measure the bearing chamber size to determine the amount of wear, and perform flaw detection on the end cover bearing to assess the repairability and formulate a repair process. According to the wear amount of the end cover, remove 0.5mm of the surface fatigue layer on one side as the processing surface.

[0074] The second step of the repair process: According to the material configuration of the end cover, select the metal alloy powder No. 1 required for laser cladding, and its powder composition is C0.27\Mn0.42\Si0.3\Cr3.74\Mo0.36\Ni5.6\Fe remainder. Install the end cover on the fixture, debug the laser equipment, and set the process parameters of laser cladding: laser power 3000W, scanning speed 7mm / s, powder feeding amount 5g / min, spot size 7mm, and protective gas is argon. Using the synchronous powder feeding method, laser cladding is performed on the end cover bearing chamber, and it is found that the cladding layer on the surface of the end cover bearing chamber cannot be formed.

[0075] The difference between this comparative example and Example 1 is that the parameters of laser cladding are adjusted in terms of power, spot diameter and scanning speed of laser cladding.

[0076] Comparative Example 3:

[0077] The difference between this comparative example and Example 1 is that the powder for laser cladding is powder No. 3, and its powder composition is C0.08Cr17.0Ni50Co1.0Mo2.8Al0.2Ti0.65Fe remainder. The end cover is mounted on the fixture, the laser equipment is debugged, and the process parameters of laser cladding are set: laser power 2000W, scanning speed 5mm / s, powder feeding amount 5g / min, spot size 5mm, and protective gas is argon. The end cover bearing chamber is laser clad by synchronous powder feeding, and the thickness of the cladding layer is 1mm.

[0078] The third step is machining after cladding: Use electronic measuring tools (accuracy 0.001mm) on the grinder to measure the diameter edge size of the end cover bearing chamber and restore it. The restored size is best in the center of the tolerance zone.

[0079] The fourth step is post-cladding inspection: The repaired end cover is subjected to penetrant testing and cracks are found.

[0080] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the embodiments made by those skilled in the art fall within the scope defined by the claims attached to the present invention.

Claims

1. A laser cladding repair method, characterized in that: The method comprises preparing laser cladding powder, laser cladding the component to be repaired, and obtaining a cladding layer, wherein the toughness of the cladding layer is 1.1 to 1.3 times that of the component to be repaired; The tensile strength of the laser cladding powder meets the tensile strength requirement of the part to be repaired, the elastic modulus of the laser cladding powder is 0.9 to 1.1 times the elastic modulus of the part to be repaired, the thermal expansion coefficient of the laser cladding powder is 0.9 to 1.1 times the thermal expansion coefficient of the part to be repaired, and the yield strength of the laser cladding powder is 0.9 to 1.1 times the stress of the part to be repaired.

2. The laser cladding repair method according to claim 1, characterized in that: The parts to be repaired include motor end covers or motor support parts.

3. The laser cladding repair method according to claim 1, characterized in that: The component to be repaired is a motor end cover, and the yield strength of the laser cladding powder is 0.9 to 1.1 times the stress at the bearing chamber of the motor end cover.

4. The laser cladding repair method according to claim 1, characterized in that: The laser cladding powder comprises the following components in weight percentage: C 0.25%-0.35%, Mn 0.35%-0.45%, Si 0.2%-0.4%, Cr 2%-4%, Mo 0.1%-0.5%, Ni 3-8%, and the balance is Fe.

5. The laser cladding repair method according to claim 4, characterized in that: The laser cladding powder comprises the following components in weight percentage: C 0.25%-0.3%, Mn 0.4%-0.45%, Si 0.2%-0.3%, Cr 3%-4%, Mo 0.3%-0.5%, Ni 3-6%, and the balance is Fe.

6. The laser cladding repair method according to claim 4, characterized in that: The process parameters of the laser cladding are: laser power of 1900-2100W, scanning speed of 5-7mm / s, powder feeding rate of 4-6g / min, spot size of 2.5-7mm, and protective gas of argon.

7. The laser cladding repair method according to claim 6, characterized in that: The process parameters of the laser cladding are: laser power of 1900-2000W, scanning speed of 5-6mm / s, powder feeding amount of 4-5g / min, spot size of 5-7mm, and protective gas of argon.

8. The laser cladding repair method according to claim 1, characterized in that: Laser cladding adopts synchronous powder feeding method.

9. The laser cladding repair method according to claim 1, characterized in that: The following steps are also included before laser cladding: A. Clean the parts to be repaired, measure the dimensions, and determine the worn parts and amount of wear; B. Perform flaw detection on the parts to be repaired after cleaning in A to facilitate failure analysis and life analysis; C. According to the wear amount of the parts to be repaired in A, remove the fatigue layer by 0.5-1mm.

10. The laser cladding repair method according to claim 1, characterized in that: The following steps are also included before laser cladding: After completing the laser cladding of the repaired part, the end cap is machined according to the required size of the repaired part, and the size requirements of the drawing are met, including roughness and dimensional tolerance. Carry out dimensional inspection on the parts to be repaired after processing; After the dimensional inspection is completed and qualified, the parts to be repaired are subjected to penetrant testing to confirm that there are no cracks on the surface.

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