A laser-directed energy deposition repair method for aluminum alloy parts

Abstract

This invention discloses a laser-directed energy deposition (LDED) repair method for aluminum alloy parts. The method involves using aluminum-magnesium-zinc alloy powder as the repair material, repairing the aluminum alloy base material using LDED technology under a protective gas mixture of argon and nitrogen, and then heat-treating the repaired aluminum alloy. This repair method ensures good bonding between the repaired area and the base material, and eliminates crack defects at the interface, thus achieving the goal of reusing damaged aluminum alloy parts.

Description

Technical Field

[0001] This invention belongs to the field of metal material surface treatment technology, specifically relating to a laser-directed energy deposition repair method for aluminum alloy parts. Background Technology

[0002] Aluminum alloys are widely used as structural materials in the transportation sector due to their excellent properties of high strength and low density.

[0003] However, as the service life increases, the damage to the load-bearing structure of aluminum alloy parts during service will seriously reduce their service life and load-bearing strength, making the parts prone to breakage.

[0004] Repairing damaged parts has become an urgent problem to be solved. Traditional repair methods such as welding and thermal spraying are no longer effective in repairing large damaged areas of aluminum alloy parts. For such damaged aluminum alloy parts, the current main approach is to remelt the parts and replace them, but this results in a lot of waste and huge costs.

[0005] Laser-guided energy deposition (LAD) technology offers advantages such as short processing time, high material utilization, high precision, low cost, and the ability to repair parts with large damaged areas. It has received widespread attention in the field of repair in recent years.

[0006] However, due to the high laser reflectivity of aluminum-based alloys, the use of laser-directed energy deposition technology to repair aluminum alloy parts results in insufficient laser energy absorption and excessively high local temperatures in the parts. Currently, it is difficult to completely eliminate problems such as cracks easily appearing at the joints of repaired aluminum alloy parts. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0009] One objective of this invention is to provide a laser-directed energy deposition repair method for aluminum alloy parts, which meets the requirements of good bonding between the repaired part and the base material and no crack defects at the interface, thereby achieving the purpose of reusing damaged aluminum alloy parts.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a laser-directed energy deposition repair method for aluminum alloy parts, comprising: using aluminum-magnesium-zinc alloy powder as the repair material, repairing the aluminum alloy base material using laser-directed energy deposition technology under the condition of a protective gas mixture of argon and nitrogen, and heat-treating the repaired aluminum alloy.

[0011] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, wherein the aluminum alloy base material is 7050, 7A01 or 7A05 aluminum alloy.

[0012] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the aluminum-magnesium-zinc alloy powder, by mass percentage, consists of 8-12% magnesium powder, 1-2.4% zinc powder, 0.2-1% scandium powder, 0.2-1% zirconium powder, 0.4-1% silicon powder, 0.6-1.2% manganese powder, 0.2-0.6% copper powder, with the balance being aluminum powder.

[0013] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the protective gas, by volume ratio, has an argon content of 85% to 95%, a nitrogen content of 5% to 15%, and an oxygen content of ≤900ppm.

[0014] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the laser-directed energy deposition technology has the following process conditions: unidirectional scanning mode, laser power 1400-1800W, scanning rate 600-1000mm / min, scanning interval 0.8-1.2mm, single-layer lifting height 0.3-0.7mm, powder feeding rate 0.5-1.1r / min, and gas flow rate 2-7L / min.

[0015] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the repair process involves preheating the parts to be repaired. The preheating process uses a laser with a power of 1500-1900W, a laser scanning rate of 1200-1800mm / min, and a serpentine reciprocating scanning method.

[0016] In a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the repair volume is 1.1 to 1.3 times the actual volume to be repaired.

[0017] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the heat treatment involves heating the aluminum alloy to 400-500°C and holding it at that temperature for 1-2 hours, then holding it at 100-150°C for 22-24 hours, followed by air cooling.

[0018] As a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the method further includes: before laser repair, grinding and cleaning the surface of the part and dyeing it black with black dye.

[0019] In a preferred embodiment of the laser-directed energy deposition repair method for aluminum alloy parts of the present invention, the aluminum-magnesium-zinc alloy powder used for repair is spherical powder.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention provides a novel aluminum-magnesium-zinc alloy powder for repairing aluminum alloy parts. Repairing is performed under a protective atmosphere of nitrogen and argon. The MgZn2 and AlN generated during the repair process improve the mechanical properties at the interface between the repaired area and the base material. Based on this, the process is adjusted, including blackening the repaired parts, preheating the repaired parts, and using a unidirectional scanning method, to alleviate the problems of uneven temperature distribution and weak bonding at the interface. Finally, heat treatment is performed on the parts to further improve their mechanical properties, achieving the goal of defect control and improved mechanical properties in the laser repair process of aluminum alloy components. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 This is a morphology diagram of the aluminum-magnesium-zinc alloy repair powder of Example 1 of the present invention;

[0024] Figure 2 This is a metallographic image of the interface between the repair area and the parent material in Embodiment 1 of the present invention;

[0025] Figure 3 This is a metallographic image of the interface between the repair area and the parent material in Embodiment 2 of the present invention;

[0026] Figure 4 This is a metallographic image of the interface between the repair area and the parent material in Embodiment 3 of the present invention;

[0027] Figure 5This is a metallographic image of the interface between the repair area and the parent material in Embodiment 4 of the present invention;

[0028] Figure 6 This is a metallographic image of the interface between the repair area and the parent material in Embodiment 5 of the present invention;

[0029] Figure 7 This is a metallographic image of the interface between the repair area and the parent material in Comparative Example 1 of the present invention;

[0030] Figure 8 This is a metallographic image of the interface between the repair area and the parent material in Comparative Example 2 of the present invention;

[0031] Figure 9 This is a metallographic image of the interface between the repair area and the parent material in Comparative Example 3 of the present invention. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0035] Example 1

[0036] This embodiment provides a method for repairing aluminum alloy parts using aluminum-magnesium-zinc alloy powder as the repair material and laser-directed energy deposition technology. The entire repair process maintains an atmosphere of argon and nitrogen mixture within the forming chamber, and pre-existing gaps in the aluminum alloy are repaired.

[0037] The specific steps are as follows:

[0038] (1) The base material for repair was selected as 7050 aluminum alloy, and aluminum-magnesium-zinc alloy powder was selected as the repair material. The chemical composition of the repair powder and the base material is shown in Table 1.

[0039] Table 1

[0040] Material Aluminum-magnesium-zinc alloy powder 7050 aluminum alloy Mg 10 2 Zn 2 6.1 Sc 0.6 - Zr 0.6 0.1 Si 0.4 0.1 Mn 0.8 0.08 Cr - 0.02 Fe - 0.01 Ti - 0.05 Cu 0.4 2.1 Al margin margin

[0041] (2) After placing the repair powder in a vacuum drying oven, a vacuum was drawn, and the mixture was heated for 9 hours at 100℃. Once dried, the powder was placed in a powder feeder. The powder morphology is shown in [reference needed]. Figure 1 .

[0042] (3) The substrate is processed and repaired into a V-shaped bevel by wire cutting, machining and other methods. The bevel angle is 135° and the depth is 10mm.

[0043] (4) Use sandpaper to polish the part to be repaired in step (3) until the surface of the part is smooth and has a metallic luster, and clean the surface of the part with alcohol.

[0044] (5) After cleaning, place the parts to be repaired into a vacuum drying oven, set the heating time to 30 minutes and the heating temperature to 100℃.

[0045] (6) Dye the surface of the part to be repaired black with liquid organic dye.

[0046] (7) Introduce protective gas into the molding chamber, wherein the argon content is 90% and the nitrogen content is 10% by volume fraction.

[0047] (8) The repaired parts are preheated. The preheating parameters are: laser power 1600W, laser scanning rate 1600mm / min, and scanning mode is serpentine reciprocating.

[0048] (9) Repair was performed using a laser-guided energy deposition (LAD) system with a unidirectional scanning mode. The laser power was set to 1600W, the scanning rate to 800mm / min, the scanning interval to 1.0mm, the single-layer lifting height to 0.5mm, the powder feed rate to 0.6r / min, and the gas flow rate to 5L / min. The repair volume in the program was set to 1.2 times the actual volume to be repaired.

[0049] (10) Heat treatment of the repaired parts; the specific process of heat treatment is to place the repaired parts in the furnace and heat them to 450℃ for 1.5h, then heat them at 120℃ for 24h, and then air cool them after taking them out of the furnace.

[0050] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 2 As shown in the figure. The results indicate that the repaired part has good metallurgical bonding, and there are no obvious crack defects at the interface between the repaired area and the base material. The yield strength of the tensile specimen including the repaired area and the base material is 223 MPa, the tensile strength reaches 343 MPa, and the elongation is 17.5%.

[0051] Example 2

[0052] This embodiment 2 provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from embodiment 1 is that the process of introducing 90% argon and 10% nitrogen into the forming chamber in embodiment 1 is replaced by introducing 85% argon and 15% nitrogen into the forming chamber.

[0053] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 3 As shown in the figure. The results show that there are no obvious crack defects at the interface between the repaired area and the base material. The yield strength of the repaired part is 218 MPa, the tensile strength is 335 MPa, and the elongation is 15%.

[0054] Example 3

[0055] This embodiment 3 provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from embodiment 1 is that the laser repair parameters in embodiment 1 are changed to laser power of 1800W, scanning rate of 600mm / min, scanning spacing of 1.2mm, single-layer lifting height of 0.4mm, powder feeding amount of 0.8r / min, and gas flow rate of 6L / min.

[0056] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 4 As shown in the figure. The results show that there are no obvious crack defects at the interface between the repaired area and the base material. The yield strength of the repaired part is 215 MPa, the tensile strength is 335 MPa, and the elongation is 16.5%.

[0057] Example 4

[0058] This embodiment 4 provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from embodiment 1 is that the specific heat treatment process in embodiment 1 is changed to placing the repaired parts in a furnace and heating them to 400°C for 1.5 hours, then holding them at 120°C for 22 hours, and then air cooling them after removing them from the furnace.

[0059] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 5 As shown in the figure. The results show that there are no obvious crack defects at the interface between the repaired area and the base material. The yield strength of the repaired part is 226 MPa, the tensile strength is 328 MPa, and the elongation is 15.5%.

[0060] Example 5

[0061] This embodiment 5 provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from embodiment 1 is that the repair powder composition in embodiment 1 is changed to 12% magnesium powder, 2% zinc powder, 0.6% scandium powder, 0.6% zirconium powder, 0.4% silicon powder, 0.8% manganese powder, 0.4% copper powder, and the balance is aluminum.

[0062] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 6As shown in the figure. The results show that there are no obvious crack defects at the interface between the repaired area and the base material. The yield strength of the repaired part is 223 MPa, the tensile strength is 320 MPa, and the elongation is 16%.

[0063] Comparative Example 1

[0064] This comparative example provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from the embodiment is that the process parameters are changed to laser power of 1300W, scanning rate of 500mm / min, scanning spacing of 0.7mm, single-layer lifting height of 0.8mm, powder feeding amount of 1.2r / min, and air flow rate of 8L / min.

[0065] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 7 As shown in the figure. The results show that a large number of cracks appeared at the interface of the repaired part, and the surface forming quality of the cladding layer was poor. The mechanical properties of the repaired part were significantly reduced, with a yield strength of 115 MPa, a tensile strength of 196 MPa, and an elongation of 6.5%.

[0066] Comparative Example 2

[0067] This comparative example provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from the example is that the repair powder composition in Example 1 is changed to 14% magnesium powder, 3% zinc powder, 1.2% scandium powder, 1.2% zirconium powder, 0.2% silicon powder, 0.4% manganese powder, 0.8% copper powder, and the balance is aluminum powder.

[0068] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 8 As shown in the figure. The results show that a large number of cracks appeared at the interface of the repaired part, and the surface forming quality of the cladding layer was poor. The mechanical properties of the repaired part were significantly reduced, with a yield strength of 106 MPa, a tensile strength of 185 MPa, and an elongation of 5.5%.

[0069] Comparative Example 3

[0070] This comparative example provides a laser repair process for damaged 7-series aluminum alloy parts. The difference from the example is that the heat treatment parameters are changed, the aluminum alloy to be repaired is heated to 380°C and held for 2 hours, then held at 80°C for 24 hours, and then air-cooled.

[0071] Metallographic image of the interface between the repaired area and the parent material as shown in the figure. Figure 9 As shown in the figure. The results show that the number of crack defects at the interface of the repaired part is not significantly different from that in the example, but the mechanical properties of the repaired part are significantly reduced. The yield strength of the repaired part is 125 MPa, the tensile strength is 215 MPa, and the elongation is 6.8%.

[0072] In summary, by comparing the test results of the repaired aluminum alloy samples obtained from Examples 1-5 and Comparative Examples 1-3, it can be seen that the 7-series aluminum alloy obtained by the repair method described in this invention, upon visual observation, shows no warping of the repaired parts, and only a very small number of porosity defects exist at the interface between the repaired area and the base material. Its tensile strength can reach about 340 MPa, which meets the service requirements of aluminum alloy parts used in general rail transit. Moreover, the implementation device of this method is relatively simple and convenient to use, and it can repair relatively complex aluminum alloy parts.

[0073] This invention selects a mixture of nitrogen and argon as the protective gas during repair. A small amount of aluminum nitride is generated in the repaired part. Aluminum nitride has the characteristics of fast thermal conductivity and small coefficient of thermal expansion, which can reduce the warping of the repaired parts and optimize the repair effect.

[0074] The repair powder selected in this invention contains a certain amount of Mg and Zn elements. During the repair process, more MgZn2 can be formed at the interface, which can effectively improve the bonding strength at the interface, resulting in parts with better repair effects and extending the service life of the parts.

[0075] This invention dyes the part to be repaired black, which reduces the laser reflectivity at that location, allowing the surface of the part and the fed powder to melt fully, reducing cracks at the interface of the repaired part, and optimizing the repair effect.

[0076] The scanning strategy of this invention adopts a unidirectional scanning method and preheats the parts at the same time, which alleviates the phenomenon of excessive local temperature during the repair process and suppresses warping and other phenomena.

[0077] This invention involves heat treatment of the repaired parts. Solid solution treatment allows the non-equilibrium phase with a large heat-affected zone to dissolve into the matrix as much as possible, thereby increasing the driving force of phase transformation during aging. This enables more aging phases to precipitate during the aging process, further improving the mechanical properties of the repaired sample.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A laser-directed energy deposition repair method for aluminum alloy parts, characterized in that: include, Using aluminum-magnesium-zinc alloy powder as the repair material, the aluminum alloy base material is repaired by laser directional energy deposition technology under the protective gas of argon and nitrogen mixture. The repaired aluminum alloy is then heat-treated. Before laser repair, the surface of the parts is polished, cleaned and dyed black with black dye. The aluminum alloy base material is 7050, 7A01 or 7A05 aluminum alloy; The aluminum-magnesium-zinc alloy powder, by mass percentage, consists of 8-12% magnesium powder, 1-2.4% zinc powder, 0.2-1% scandium powder, 0.2-1% zirconium powder, 0.4-1% silicon powder, 0.6-1.2% manganese powder, 0.2-0.6% copper powder, with the balance being aluminum powder; The protective gas, by volume ratio, has an argon content of 85%–95%, a nitrogen content of 5%–15%, and an oxygen content of ≤900ppm. The laser-directed energy deposition technology has the following process conditions: unidirectional scanning mode, laser power 1400-1800W, scanning rate 600-1000mm / min, scanning interval 0.8-1.2mm, single-layer lifting height 0.3-0.7mm, powder feeding rate 0.5-1.1r / min, and gas flow rate 2-7L / min. The heat treatment involves heating the repaired aluminum alloy to 400–500°C and holding it at that temperature for 1–2 hours, then holding it at 100–150°C for 22–24 hours, followed by air cooling.

2. The laser-directed energy deposition repair method for aluminum alloy parts as described in claim 1, characterized in that: The repair process involves preheating the parts to be repaired using a laser with a power of 1500–1900W and a scanning rate of 1200–1800 mm / min, employing a serpentine reciprocating scanning method.

3. The laser-directed energy deposition repair method for aluminum alloy parts as described in claim 1, characterized in that: The repair is carried out, and the repair volume is 1.1 to 1.3 times the actual volume to be repaired.

4. The laser-directed energy deposition repair method for aluminum alloy parts as described in any one of claims 1 to 3, characterized in that: The aluminum-magnesium-zinc alloy powder used for repair is spherical powder.

Images