A repair device for a rotor made of heterogeneous materials and a laser 3D printing repair method

Abstract

The present invention discloses a repair device and a laser 3D printing repair method for a heterogeneous material rotor. By adapting a set of repair devices and a corresponding repair method to the rotor, the local area of ​​the damaged and failed rotor end cover can be subjected to integrated surface repair such as high-performance laser preheating, laser forming and laser stress relief annealing, thereby making up for the inherent limitation of SLM technology that is difficult to use for repair and remanufacturing, providing a new repair solution for the surface remanufacturing of liquid immiscible heterogeneous materials, reducing the scrap rate of the rotor, reducing the corresponding maintenance cost, and expanding the application scope of laser 3D printing technology in remanufacturing.

Description

Technical Field

[0001] The present invention relates to the field of metal additive manufacturing, and in particular to a repair device for a heterogeneous material rotor and a laser 3D printing repair method. Background Art

[0002] Precision rotor parts often produce surface cracks due to heavy load impact, high load wear and repeated high temperature, which leads to wear failure. To solve this problem, aircraft engine rotors often use special methods to prepare a copper protective layer on the surface of steel structural parts. However, after the surface failure of special rotors, further surface repair is urgently needed to restore their performance. However, since iron-copper is a liquid difficult / immiscible material, traditional solid connection processes (such as hot / cold spraying, PVD, CVD, diffusion welding, etc.) are commonly used to repair the corresponding structural parts. However, the connection layer prepared by this method is extremely thin and has weak bonding strength, and the possibility of cracking after the structural parts are repaired is still high.

[0003] Selective laser melting (SLM) technology is one of the important technologies in the field of metal additive manufacturing. It uses a high-energy-density laser as a heat source. The laser spot is concentrated in the range of 20 to 100 μm. Spherical metal powder with a particle diameter of 5 to 50 μm is selected to melt. Complex metal components with high degrees of freedom can be obtained, and nearly 100% high-density parts are generated. The surface roughness can reach 20 to 30 μm, and the dimensional accuracy can reach 20 to 50 μm. Once invented, it has been widely favored in the manufacture of high-precision parts such as special-shaped curved surfaces and complex internal structures, especially in aerospace parts such as turbine rotors and impeller blades. However, SLM is currently only used for the integrated forming and manufacturing of complex structural parts. In terms of surface repair, it is extremely difficult to achieve surface repair between dissimilar material structures such as iron-copper liquids that are difficult / immiscible, which also poses a great challenge to the surface repair and remanufacturing of special-shaped and heterogeneous material parts.

[0004] In addition, in order to reduce the thermal stress in the SLM process and reduce the possibility of warping and cracking of parts, Chinese patent CN103100713A discloses "Preheating device and preheating method for powder feeding tube of selective laser selective melting SLM equipment", which proposes a method of preheating metal powder by using electromagnetic induction to heat the powder carrier tube. Although this method can preheat metal powder, the powder in the powder carrier tube is not heated evenly, and the entire powder carrier tube is heated, which not only has low heating efficiency but also large energy loss. In addition, Chinese patent CN106623919A discloses "A powder preheating device and preheating method for laser selective melting equipment", which proposes to use multiple heating units embedded in the side of the forming cylinder body to heat the forming cylinder body. This method can make the parts cool slowly during the printing process and reduce internal stress concentration. However, if the heating unit performs cyclic heating, cooling and reheating of the forming cylinder for a long time, it will affect its overall shape and internal structure, and there is no temperature monitoring function, and its heating temperature cannot be monitored in real time. However, for parts that are significantly sensitive to preheating temperature, long-term, integrated preheating of the workpiece to be repaired is not in line with the requirements. Therefore, how to avoid overall high-temperature preheating and prepare heterogeneous material rotors with good metallurgical bonding interfaces has become one of the urgent problems to be solved. Summary of the invention

[0005] In view of the above problems, the present invention proposes a repair device for a heterogeneous material rotor and a laser 3D printing repair method, aiming to solve the problem that the existing SLM technology cannot repair and form liquid heterogeneous materials that are difficult to mix and melt.

[0006] In order to solve the above technical problems, the first aspect of the present invention proposes a repair device for a heterogeneous material rotor, comprising an outer ring, an inner ring and an embedded component whose upper end surfaces are located in the same horizontal plane, and the outer ring, the inner ring and the embedded component are contoured according to the shape of the end cover of the rotor, wherein the outer ring has an interference fit with the outer wall of the rotor, the inner ring has an interference fit with the inner wall of the rotor, and the embedded component has an interference fit with the rotor slot of the rotor.

[0007] A second aspect of the present invention provides a laser 3D printing repair method for the above-mentioned repair device, comprising the following steps:

[0008] Step 1: Install the rotor to be repaired into the repair device, expose the end cover of the rotor outside the repair device, and process the residual copper layer of the end cover and the upper end surface of the repair device to the same level to form a part to be repaired;

[0009] Step 2: Clamp the component to be repaired as a whole onto the operating table of the SLM additive manufacturing system, establish a virtual model of the defective part according to the defective part of the end cover, and import the virtual model of the defective part into the computer unit of the SLM additive manufacturing system to generate a part scanning path;

[0010] Step 3: performing laser preheating pretreatment on the defective part of the end cap according to the part scanning path and preheating process parameters;

[0011] Step 4: performing laser additive manufacturing on the end cap according to the part scanning path and SLM repair process parameters;

[0012] Step 5: performing laser remelting on the end cap according to the part scanning path and remelting process parameters;

[0013] Step 6: Take out the component to be repaired as a whole from the operating table, take out the rotor from the repair device, and cut or polish the surface of the end cover according to the use requirements of the rotor.

[0014] The beneficial effects of the present invention are as follows: by adapting a set of repair devices and corresponding repair methods for the rotor, the local area of ​​the damaged and failed rotor end cover can be subjected to integrated surface repair such as high-performance laser preheating, laser forming and laser stress relief annealing, thereby making up for the inherent limitation of SLM technology that is difficult to use for repair and remanufacturing, providing a new repair solution for the surface remanufacturing of liquid immiscible heterogeneous materials, reducing the scrap rate of the rotor, reducing the corresponding maintenance costs, and expanding the scope of use of laser 3D printing technology in remanufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 An exploded view of the repair device and the rotor disclosed in the first embodiment of the present invention;

[0016] Figure 2 It is a schematic diagram of the combination of the repair device and the rotor disclosed in the first embodiment of the present invention;

[0017] Figure 3a This is a metallographic image of the rotor end cover surface after being repaired by the second embodiment of the present invention;

[0018] Figure 3b This is the metallographic image of the rotor cover surface before repair;

[0019] Figure 4a A schematic diagram of the morphology of the rotor end cover after repair by the second embodiment of the present invention;

[0020] Figure 4b This is a schematic diagram of the rotor end cover before repair;

[0021] Figure 5 Schematic diagram of the tensile fracture of the steel-copper heterogeneous material SLM repair part after tensile testing;

[0022] Figure 6 A schematic diagram of the morphology of the rotor end cover after repair by comparative example 1;

[0023] Figure 7 This is a schematic diagram of the morphology of the rotor end cover after repair through comparative example 2. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the content of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the contents.

[0025] Embodiment 1

[0026] This embodiment provides a repair device 1 for a rotor made of heterogeneous materials, such as Figure 1 , 2 As shown, it includes an outer ring 101, an inner ring 102 and an insert 103 whose upper end surfaces are located in the same horizontal plane. The outer ring 101, the inner ring 102 and the insert 103 are designed according to the shape of the end cover of the rotor 2, wherein the outer ring 101 has an interference fit with the outer wall of the rotor 2, the inner ring 102 has an interference fit with the inner wall of the rotor 2, and the insert 103 has an interference fit with the rotor slot of the rotor 2.

[0027] In this embodiment, the thickness of the outer ring 101, the inner ring 102 and the inner insert 103 is about 0.8-1.8 mm, and the length is about 2-5 mm, which are used to fix the end cover of the rotor to be repaired and provide radial support. The outer ring 101, the inner ring 102 and the inner insert 103 in the repair device 1 are all interference fit with the upper part of the rotor 2 (the repair device 1 only needs to cover the upper part of the rotor 2, and the lower part can be covered or not covered) to ensure that the repair device 1 can be perfectly fitted with the end cover of the rotor 2, so that it can effectively resist the thermal stress caused by SLM surface repair.

[0028] Embodiment 2

[0029] This embodiment proposes a laser 3D printing repair method, which is used for the above-mentioned repair device 1, and includes the following steps:

[0030] Step 1: Install the rotor 2 to be repaired into the repair device 1, so that the end cover of the rotor 2 (i.e., the upper end surface of the rotor 2) is exposed outside the repair device 1, and the residual copper layer of the end cover and the upper end surface of the repair device 1 are processed to the same horizontal plane to form a part to be repaired (i.e., a combination of the repair device 1 and the rotor 2);

[0031] The liquid refractory materials mentioned above can be any two liquid metal refractory materials, and are not limited here. In this embodiment, taking the steel-based rotor 2 and the copper protective layer as an example, because the base of the rotor 2 is Fe and the protective layer is Cu, both of which are two liquid refractory materials, the interference clamping effect of the repair device 1 on the rotor 2 can give the end cover of the rotor 2 a radially outward extending support surface, which is used as a support surface for the subsequent paving of the repair material (copper powder) during the SLM repair process. During the printing process, the 3D printing itself will warp due to huge thermal stress, resulting in failure of the repair of the parts, and the radial support provided by the repair device 1, the printed copper layer and the steel base of the rotor 2 can form a good metallurgical bond.

[0032] Preferably, in this embodiment, a repair pretreatment is also included before step 2, and the repair pretreatment includes: cleaning the surface of the end cover by shot blasting, and then cleaning the surface of the end cover by industrial alcohol to improve the surface quality of the end cover of the rotor 2.

[0033] Step 2: Clamp the component to be repaired as a whole onto the operating table of the SLM additive manufacturing system, establish a virtual model of the defective part according to the defective part of the end cap, and import the virtual model of the defective part into the computer unit of the SLM additive manufacturing system to generate a part scanning path;

[0034] Furthermore, the three-dimensional modeling software in step 2 is dedicated modeling software such as UG, Solidworks, CATIA, etc., preferably UG and Solidworks, which are used for three-dimensional inverse analysis and modeling of the removed part of the rotor 2.

[0035] Step 3: Perform laser preheating pretreatment on the defective part of the end cap according to the part scanning path and preheating process parameters;

[0036] In this embodiment, the preheating process parameters include: the SLM additive manufacturing system is adjusted to a laser power of 80W, a scanning speed of 700mm / s, a scanning spacing of 0.10mm, a protective gas concentration of 99.999vol%, and an oxygen concentration of <0.1%. During the laser preheating pretreatment process, the preheating area includes the end cap and the connection between the end cap and the repair device 1. This preheating treatment ensures that the end cap and the interface with the repair device are basically in a similar preheating processing environment, ensuring that it will not warp, deform or even crack due to the huge thermal stress generated between different materials during the subsequent SLM repair process, so that the repaired surface still has excellent effects and mechanical properties.

[0037] Step 4: Perform laser additive manufacturing on the end cap according to the part scanning path and SLM repair process parameters;

[0038] In this embodiment, the SLM repair process includes: the SLM additive manufacturing system is adjusted to a laser power of 280W, a scanning speed of 700mm / s, a scanning spacing of 0.08mm, a layer thickness of 30μm, a protective gas concentration of 99.999vol%, an oxygen concentration of <0.1%, a protective gas pressure of 0.6mbar, and a scraper powdering speed of 100mm / s. The part scanning path is set to a Z-shaped scan, and the interlayer angle is set to 67°, which can avoid a large amount of stress accumulation and microstructure homogeneity due to the scanning direction remaining in the same direction, thereby affecting the mechanical properties of the tissue after SLM repair. In fact, laser preheating pretreatment, laser additive manufacturing, and laser remelting treatment all require Z-shaped scanning with an interlayer angle of 67°, which will not be repeated below.

[0039] In step 4, copper alloy powder is used for SLM additive manufacturing. The copper alloy powder can be selected as spherical powder with a particle size of 15 to 53 μm, a purity of >99.0 wt.%, and an oxygen content of less than 1000 ppm. The preferred powder types are CuSn10, pure Cu powder and CuCr1Zr. In this embodiment, after the part to be repaired is placed in the SLM additive manufacturing system, CuSn10 powder is selected for additive manufacturing. The average particle size of the powder is 30.2 μm, and it has excellent sphericity, with only a small amount of satellite balls, which is suitable for SLM repair of the surface of the rotor 2 end cover.

[0040] During the laser additive manufacturing process, the protective gas may be nitrogen or argon. Preferably, argon is used, with a purity of 99.999 vol.%, and the oxygen content during the SLM manufacturing process is less than 0.15%. In this embodiment, argon is used as the protective gas throughout the laser preheating pretreatment, laser additive manufacturing, and laser remelting treatment, which will not be described in detail below.

[0041] Step 5: Perform laser remelting on the end cap according to the part scanning path and remelting process parameters;

[0042] In this embodiment, the remelting process parameters include: the SLM additive manufacturing system is adjusted to a laser power of 140W, a scanning speed of 1000mm / s, a scanning spacing of 0.08mm, a protective gas of Ar (99.999vol.%), and an oxygen concentration of <0.1%

[0043] Optionally, the laser power of the laser remelting treatment in step 5 is limited to 1 / 2 to 2 / 3 of the laser power of laser additive manufacturing, the scanning speed is limited to 1.0 to 1.5 times the scanning speed of laser additive manufacturing, and the scanning spacing remains unchanged. In this embodiment, the reason for reducing the power of the remelting treatment and increasing the scanning speed is to ensure that only the newly added SLM repair layer can be remelted, so that the holes and cracks caused by rapid solidification can be healed to further release the residual stress in the part. If the remelting power is high and the scanning speed is low, the heat affected zone after scanning will be larger, resulting in obvious tissue coarsening, which will adversely affect the organization and performance of the SLM repair layer.

[0044] Step 6: Take the entire part to be repaired out of the operating table, take the rotor 2 out of the repair device 1, and perform cutting or polishing on the surface of the end cap according to the use requirements of the rotor. Specifically, the cutting or polishing is performed according to the process card requirements and actual standards of the end cap, which are not limited here.

[0045] Compare the end cap of the repaired rotor with that of the original rotor before repair, such as Figure 3a and 3b As shown in the figure, after statistics by Image J software, the density of the repaired end cover can reach 99.9% with almost no holes, and even exceeds the density of the original rotor surface (89.2%), indicating that the prepared CuSn10 repair part can be regarded as completely dense, and the prepared repair part meets the use requirements of the original part.

[0046] See also Figure 4a and 4b The macroscopic comparison of the rotor morphology before and after repair shows that the copper layer on the rotor surface is severely worn before repair, but the surface is as smooth as new after repair, and the roughness is reduced to Ra = 1.09μm, which can meet the use requirements. In order to further test the mechanical properties of the prepared repair layer, the hardness test specimens and tensile test specimens were prepared and tested using this method and the same process. The test results after multiple measurements and statistics are shown in Table 1. The tensile fracture is shown in Table 1. Figure 5As shown. The microhardness of the original rotor is 128.2±5.18HV0.05, and the microhardness of the repaired part, i.e. the printed CuSn10 alloy, is 167.8±3.42HV0.05, indicating that the adopted SLM repair process can meet its necessary mechanical properties and service requirements. In addition, after testing with a tensile machine, it was found that the fracture position was the connection position between copper and steel, but it was found that cracks had begun to appear at the CuSn10 end, close to fracture, so the connection strength was basically close to the fracture limit of 3D printed CuSn10.

[0047] Table 1. Mechanical properties statistics of steel-copper heterogeneous material SLM repair parts

[0048]

[0049]

[0050] The average microhardness test method for the alloy sample in the embodiment is as follows: the Vickers microhardness of the sample is measured using a microhardness tester (model: Leitz Wetzlar, Germany), the load used is 50g, and the loading time is 25s. The surface roughness of the SLM sample test surface is polished to less than 0.15μm, and the microhardness values ​​at different positions on the SLM sample surface are measured, and the average value is taken after 10 measurements.

[0051] The tensile properties test method for the alloy sample in the embodiment is: tensile test is carried out at a displacement rate of 1 mm / min at room temperature according to ASTM E8 M standard. Mechanical properties including tensile strength (UTS), yield strength (YS) and fracture strain are directly read from the INSTRON tensile tester, and the elongation at break (EL) is measured according to ASTM E 111 standard, and strain failure is evaluated by a strain gauge and an electronic extensometer with a range of 10 mm installed on the gauge part of the test sample. The elastic modulus is calculated according to the stress-strain curve. For each experimental group, three samples are tested and the average value is calculated.

[0052] Comparative Example 1

[0053] In this comparative example, the repair device 1 described in Example 1 is not used for clamping. The remaining processes and parameters refer to Example 2, and the variables are controlled to be the repair device 1. During the SLM manufacturing process, there are great thermal stress and structural stress between the copper layer and the steel material itself, and the SLM copper layer has a good microstructure and excellent mechanical properties. Therefore, the copper layer after SLM repair tears the inside of the steel matrix, resulting in the following Figure 6 The visible cracks shown resulted in a failed repair.

[0054] Comparative Example 2

[0055] In this comparative example, the repair device 1 described in Example 1 is used for clamping, and the laser power of the laser remelting treatment is adjusted to 1 times the laser power of the laser additive manufacturing (this power has exceeded the recommended upper limit of the laser power of the laser remelting treatment in Example 2), and the scanning speed of the laser remelting treatment is adjusted to 0.8 times the scanning speed of the laser additive manufacturing (this speed is lower than the recommended lower limit of the scanning speed of the laser remelting treatment in Example 2), and the variables are controlled to be the laser power and scanning speed of the laser remelting treatment. Since the process parameters used for the laser remelting treatment in this comparative example are not the parameters recommended in Example 2, the higher heat input leads to a large amount of heat accumulation, which in turn causes the rotor surface to have a similar appearance after repair. Figure 7 The obvious oxidation discoloration shown causes the parts to fail to be repaired.

[0056] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser 3D printing repair method, used for a repair device for a heterogeneous material rotor, the repair device for a heterogeneous material rotor comprising an outer ring, an inner ring and an inner insert whose upper end faces are located at the same horizontal plane, the outer ring, the inner ring and the inner insert are designed according to the shape of the end cover of the rotor, wherein: The outer ring is interference fit with the outer wall of the rotor, the inner ring is interference fit with the inner wall of the rotor, and the embedded component is interference fit with the rotor slot of the rotor, and is characterized in that it includes the following steps: Step 1: Install the rotor to be repaired into the repair device, expose the end cover of the rotor outside the repair device, and process the residual copper layer of the end cover and the upper end surface of the repair device to the same level to form a part to be repaired; Step 2: Clamp the component to be repaired as a whole onto the operating table of the SLM additive manufacturing system, establish a virtual model of the defective part according to the defective part of the end cover, and import the virtual model of the defective part into the computer unit of the SLM additive manufacturing system to generate a part scanning path; Step 3: performing laser preheating pretreatment on the defective part of the end cap according to the part scanning path and preheating process parameters; Step 4: performing laser additive manufacturing on the end cap according to the part scanning path and SLM repair process parameters; Step 5: performing laser remelting processing on the end cap according to the part scanning path and remelting process parameters; Step 6: Take out the component to be repaired as a whole from the operating table, take out the rotor from the repair device, and cut or polish the surface of the end cover according to the use requirements of the rotor.

2. The laser 3D printing repair method according to claim 1, characterized in that: The preheating process parameters include: the SLM additive manufacturing system is adjusted to a laser power of 80 W, a scanning speed of 700 mm / s, a scanning spacing of 0.10 mm, a protective gas concentration of 99.999 vol%, and an oxygen concentration of <0.1%.

3. The laser 3D printing repair method according to claim 2, characterized in that: During the laser preheating pretreatment process, the preheated area includes the end cap and the connection portion between the end cap and the repair device.

4. The laser 3D printing repair method according to claim 1, characterized in that: The SLM repair process includes: the SLM additive manufacturing system is adjusted to a laser power of 280 W, a scanning speed of 700 mm / s, a scanning spacing of 0.08 mm, a layer thickness of 30 μm, a protective gas concentration of 99.999 vol%, an oxygen concentration of <0.1%, a protective gas pressure of 0.6 mbar, and a scraper powdering speed of 100 mm / s.

5. The laser 3D printing repair method according to claim 4, characterized in that: The part scanning path is set to a Z-shaped scan, and the inter-layer angle is set to 67°.

6. The laser 3D printing repair method according to claim 4, characterized in that: In the laser additive manufacturing process, SLM additive manufacturing uses copper alloy powder, and the copper alloy powder is a spherical powder with a particle size of 15-53 μm, a purity of >99.0wt.%, and an oxygen content of less than 1000 ppm.

7. The laser 3D printing repair method according to claim 4, characterized in that: During the laser additive manufacturing process, the protective gas is nitrogen or argon.

8. The laser 3D printing repair method according to claim 1, characterized in that: The remelting process parameters include: the SLM additive manufacturing system is adjusted to a laser power of 140 W, a scanning speed of 1000 mm / s, a scanning spacing of 0.08 mm, a protective gas concentration of 99.999 vol.%, and an oxygen concentration of <0.1%.

9. The laser 3D printing repair method according to claim 1, characterized in that: Before step 2, a repair pretreatment is also included, and the repair pretreatment includes: cleaning the surface of the end cover by shot blasting, and then cleaning the surface of the end cover by industrial alcohol.

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