A method for laser-directed energy deposition additive manufacturing of metal surfaces

Abstract

This invention discloses a method for laser-directed energy deposition additive manufacturing of metal surfaces, belonging to the field of laser additive manufacturing technology. The method includes: S1, performing a first heat treatment on a high thermal conductivity metal substrate to reduce its thermal conductivity; S2, performing surface cleaning pretreatment on the metal substrate after reducing its thermal conductivity; and S3, performing laser-directed energy deposition additive manufacturing on the pretreated metal substrate surface. Based on this manufacturing method, this invention also provides a bimetallic component. The method of this invention is convenient to operate, precise, and reliable. It can improve the energy utilization rate during laser processing, avoid the problems of discontinuous or even spherical molten channels caused by short melt pool time and insufficient spreading, does not increase substrate deformation, does not reduce material performance, and can improve the quality of laser-directed energy deposition additive manufacturing of high thermal conductivity materials.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing technology, and more specifically, relates to a method for laser-directed energy deposition additive manufacturing of metal surfaces. Background Technology

[0002] High thermal conductivity metals such as copper alloys and aluminum alloys are widely used in industry due to their extremely high thermal conductivity. However, these metal materials generally have low strength and hardness, and poor wear resistance. To improve the service life of their components, it is generally necessary to additively manufacture a certain thickness of high-strength material on the surface of the component. Laser-directed energy deposition (LDED) is one of the most commonly used methods. This involves using the high thermal conductivity metal component as a substrate and then using LDED to manufacture a certain thickness of high-strength or high-wear-resistant material on the substrate, such as creating a nickel or steel reinforcing layer on the surface of copper and aluminum alloys. However, additive manufacturing suffers from drawbacks such as short molten pool duration, insufficient spreading, highly discontinuous or even spherical melt channels after forming, poor quality of the additive layer, and susceptibility to metallurgical defects such as voids.

[0003] Currently, one common solution is to increase the input laser energy. This method can alleviate the harm of insufficient molten pool spreading to some extent, but it also increases the deformation of the substrate. The increased substrate size requires even greater laser energy, which cannot be quantitatively calculated, and it cannot completely solve the problem of metallurgical defects such as pores generated during the forming process. Another approach is to use surface modification methods to increase the material's absorption rate of laser light, such as electro / chemical plating, vapor deposition, cold / hot / plasma spraying, etc. However, these methods have similar effects to increasing the input laser energy; they still cause increased substrate deformation and may introduce foreign elements, leading to a decline in material properties. Summary of the Invention

[0004] In view of the shortcomings of existing technologies and the need for improvement, this invention provides a method for additive manufacturing of metal surfaces by laser directional energy deposition, which aims to improve the forming quality of high thermal conductivity metal additive manufacturing without increasing substrate deformation or reducing material properties.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for laser-directed energy deposition additive manufacturing of a metal surface is provided, comprising:

[0006] S1. Perform a first heat treatment on the high thermal conductivity metal substrate to reduce the thermal conductivity of the metal substrate;

[0007] S2. Perform surface cleaning pretreatment on the metal substrate after reducing thermal conductivity;

[0008] S3. Perform laser-directed energy deposition additive manufacturing on the pretreated metal substrate surface.

[0009] Furthermore, in S1, after the first heat treatment, the following steps are also included:

[0010] The area to be deposited on the metal substrate is scanned with a laser to induce an over-dissolved state in the area.

[0011] Furthermore, in S1, the thermal conductivity of the metal substrate is reduced to below 50% of its maximum thermal conductivity.

[0012] Furthermore, in S1, the thermal conductivity of the metal substrate is reduced to a minimum thermal conductivity state.

[0013] Furthermore, it also includes:

[0014] S4. Perform a second heat treatment on the workpiece obtained by laser-directed energy deposition additive manufacturing to improve the thermal conductivity of the metal substrate.

[0015] Furthermore, the first heat treatment includes: solution heat treatment, cold rolling-solution heat treatment, or chemical heat treatment;

[0016] The second heat treatment includes: aging precipitation heat treatment or annealing heat treatment.

[0017] Furthermore, the high thermal conductivity metal matrix is ​​a precipitation-strengthened high thermal conductivity alloy.

[0018] Furthermore, the precipitation-strengthened high thermal conductivity alloy includes copper alloys or aluminum alloys.

[0019] Furthermore, the manufacturing method of the high thermal conductivity metal matrix includes: casting, forging, rolling, laser powder bed manufacturing, electron beam powder bed manufacturing, laser filament forming, or electric arc filament forming.

[0020] According to another aspect of the invention, a bimetallic component is provided, which is prepared by the method described in any one of the first aspects.

[0021] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0022] (1) The method of the present invention reduces the thermal conductivity of the metal substrate by heat treatment and cleaning, and then performs additive manufacturing. This can reduce the heat dissipation of the metal substrate during additive manufacturing, thereby improving the energy utilization rate during laser processing. It avoids the problem of discontinuous or even spherical forming channels caused by short melting time and insufficient spreading of the molten pool, thus improving the forming quality. At the same time, the present invention solves the problems in the additive manufacturing process by first reducing the thermal conductivity of the metal substrate, and then further increases the thermal conductivity of the metal substrate to give full play to the role of the high thermal conductivity metal substrate. This method will not increase the deformation of the substrate, nor will it introduce foreign elements, thus not reducing the performance of the material, and further improving the forming quality.

[0023] (2) Preferably, after the metal substrate is subjected to the first heat treatment, the laser is used to scan the area to be deposited. Due to the ultra-high cooling rate during laser scanning, the material in the laser action area is in an oversolid state. The overall heat treatment combined with local laser heat treatment further reduces the thermal conductivity of the substrate and further improves the forming quality.

[0024] (3) Preferably, for the same metal matrix material, when the thermal conductivity is reduced to less than 50% of its maximum thermal conductivity, the heat dissipation of the metal matrix can be reduced, the energy utilization rate during subsequent laser processing can be improved, and the forming quality can be improved.

[0025] (4) Preferably, when the thermal conductivity of the metal substrate is reduced to the lowest thermal conductivity state, the heat dissipation of the metal substrate can be reduced to the greatest extent, the energy utilization rate during laser processing is the highest, and the forming quality is the best.

[0026] (5) By performing a second heat treatment on the workpiece obtained by laser-directed energy deposition additive manufacturing, the thermal conductivity of the metal substrate is improved, so as to give full play to the value of the high thermal conductivity metal substrate.

[0027] (6) The method of the present invention does not have any special requirements for the manufacturing method of the high thermal conductivity metal matrix. Commonly used manufacturing methods are applicable, and all precipitation-strengthened high thermal conductivity alloys can be used as metal matrices, with a wide range of applications.

[0028] (7) The method of the present invention can process complex structures such as rings and irregular shapes, and has a more obvious advantage in processing large parts, and has a wide range of applications.

[0029] In summary, the method of the present invention is convenient to operate, precise and reliable, and can improve the quality of laser-directed energy deposition additive manufacturing of high thermal conductivity materials. Attached Figure Description

[0030] Figure 1 This is a flowchart of the laser-directed energy deposition additive manufacturing method for metal surfaces according to the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0032] In this invention, the terms "first," "second," etc., used in the invention and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0033] like Figure 1 As shown, the metal surface laser-directed energy deposition additive manufacturing method of the present invention mainly includes the following steps:

[0034] S1. Perform a first heat treatment on the high thermal conductivity metal substrate to reduce the thermal conductivity of the metal substrate;

[0035] S2. Perform surface cleaning pretreatment on the metal substrate after reducing thermal conductivity to make it suitable for laser-directed energy deposition additive manufacturing.

[0036] S3. Perform laser-directed energy deposition additive manufacturing on the pretreated metal substrate surface.

[0037] In S1, preferably, the high thermal conductivity metal matrix is ​​a precipitation-strengthened high thermal conductivity alloy, such as copper alloy or aluminum alloy.

[0038] The first heat treatment includes, but is not limited to, any one of solution heat treatment, cold rolling-solution heat treatment, or chemical heat treatment.

[0039] As a preferred option, the thermal conductivity of the metal matrix is ​​reduced to below 50% of its maximum thermal conductivity. For the same metal matrix material, when the thermal conductivity is reduced to below 50% of its maximum thermal conductivity, the heat dissipation of the metal matrix can be reduced effectively, the energy utilization rate during subsequent laser processing can be improved, and the forming quality can be enhanced.

[0040] As a further optimization, reducing the thermal conductivity of the metal substrate to its lowest possible level yields the best results. The lowest possible thermal conductivity for different metal substrates and manufacturing methods can be determined experimentally.

[0041] The manufacturing methods of high thermal conductivity metal substrates include, but are not limited to, any one of the following: casting, forging, rolling, laser powder bed manufacturing, electron beam powder bed manufacturing, laser fused wire forming, and electric arc fused wire forming.

[0042] Preferably, in step S1, after the first heat treatment, the step further includes: scanning the area to be deposited on the metal substrate with a laser to make the area in an over-solid state; due to the ultra-high cooling rate during laser scanning, the material in the laser action area is in an over-solid state. The overall heat treatment combined with local laser heat treatment can further reduce the thermal conductivity of the substrate and further improve the forming quality.

[0043] Furthermore, the method of the present invention also includes:

[0044] S4. Perform a second heat treatment on the workpiece obtained by laser-directed energy deposition additive manufacturing to improve the thermal conductivity of the metal substrate.

[0045] Preferably, the second heat treatment includes, but is not limited to, annealing heat treatment, aging precipitation heat treatment, etc.

[0046] According to another aspect of the present invention, a bimetallic component is provided, which is prepared by the above-described metal surface laser-directed energy deposition additive manufacturing method.

[0047] The method of this invention reduces the thermal conductivity of a high thermal conductivity metal substrate by heat treatment and cleaning before additive manufacturing. This reduces heat dissipation from the metal substrate during additive manufacturing, thereby improving energy utilization during laser processing. It also avoids problems such as discontinuous or even spherical weld lines caused by short melt pool time and insufficient spreading, thus improving forming quality. Furthermore, this method of first reducing the thermal conductivity of the metal substrate to solve problems in additive manufacturing, and then further increasing the thermal conductivity of the metal substrate to give full play to the function of a high thermal conductivity metal substrate, does not increase substrate deformation or introduce foreign elements, and therefore does not reduce material performance, further improving forming quality.

[0048] To further explain the method of the present invention, specific embodiments are described below. Of course, the method of the present invention is not limited to the specific materials given in the embodiments; any embodiment that conforms to the method can meet the requirements.

[0049] Example 1

[0050] Laser-directed energy deposition (LDED) additive manufacturing of GH4169 high-temperature alloy on rolled CuCr0.8 copper alloy substrate.

[0051] S1: The rolled CuCr0.8 matrix is ​​treated with a solution heat treatment process of holding at 1020℃ for 1.5h (water quenching) to ensure that all the second phase particles (Cr strengthening particles) are dissolved into the copper matrix. Under rapid cooling conditions of water quenching, a supersaturated solid solution is obtained, which minimizes the thermal conductivity of the matrix. In other embodiments, other heat treatment methods such as chemical heat treatment and cold rolling-solution heat treatment can also be used to reduce the thermal conductivity of the matrix.

[0052] S2: The substrate surface after S1 treatment is processed by machining and then cleaned by ultrasonic cleaning with alcohol.

[0053] S3: Laser-directed energy deposition additive manufacturing of Inconal 718 superalloy was performed on the treated CuCr0.8 substrate. The process parameters were: laser power 1400W, scanning speed 10mm / s, and powder feed rate 7g / min. The final In718 melt pool depth formed by laser-directed energy deposition on the solution-treated CuCr0.8 substrate was 165.0±6.3μm.

[0054] Comparative Example 1

[0055] Unlike Example 1, Comparative Example 1 directly used rolled CuCr0.8 substrate for laser-directed energy deposition, employing the same process parameters as Example 1 (laser power 1400W, scanning speed 10mm / s, powder feed rate 7g / min). The final In718 melt pool depth was 126.7±14.8μm. That is, compared to Comparative Example 1, the melt depth in Example 1 was increased by 30.2%.

[0056] Comparative Example 2

[0057] Unlike Example 1, Comparative Example 2 directly uses a rolled CuCr0.8 substrate for laser-directed energy deposition. To achieve a molten pool depth of 165.0 μm in the In718 formed by laser-directed energy deposition, 1600 W of laser energy is required under the same forming conditions. That is, compared to Comparative Example 2, Example 1 can reduce the laser energy input by 14.3%.

[0058] Example 2

[0059] Laser selective melting forming of AlSi10Mg components using laser-directed energy deposition additive manufacturing of 316L steel.

[0060] S1: The AlSi10Mg component is treated with a solution heat treatment process of holding at 540℃ for 4h (water quenching), which allows the bulk Si particles and nano-sized second-phase particles Mg2Si reinforcing particles to be dissolved into the aluminum matrix, resulting in a supersaturated solid solution and reducing the thermal conductivity of the matrix.

[0061] S2: The surface of the component after S1 treatment is sandblasted and cleaned with alcohol;

[0062] S3: Laser-directed energy deposition additive manufacturing of 316L steel on the treated AlSi10Mg component.

[0063] Example 3

[0064] Laser-directed energy deposition additive manufacturing of SiC / Al-based composite materials on the surface of extruded 7050 aluminum alloy ring parts;

[0065] S1: The extruded 7050 ring part is treated by a solution heat treatment process of holding at 480℃ / 2h (water quenching) to allow the second phase particles (Al7Cu2Fe and MgZn2) to be dissolved into the aluminum matrix, resulting in a supersaturated solid solution and reducing the thermal conductivity of the matrix.

[0066] S2: Clean and dry the parts treated in S1;

[0067] S3: Laser-directed energy deposition additive manufacturing of SiC / Al-based composite materials on the processed 7050 ring-shaped part.

[0068] Through the above three embodiments, it can be seen that, under the same process parameters, compared with direct laser-directed energy deposition on the substrate material, the embodiments of the present invention can improve the melting depth; under the same forming environment, if both achieve the same melting depth, the embodiments of the present invention require less laser energy input.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for laser-directed energy deposition additive manufacturing of metal surfaces, characterized in that, include: S1. The high thermal conductivity metal matrix is ​​subjected to a first heat treatment to reduce the thermal conductivity of the metal matrix; wherein the high thermal conductivity metal matrix is ​​a precipitation-strengthened high thermal conductivity alloy. S2. Perform surface cleaning pretreatment on the metal substrate after reducing thermal conductivity; S3. Perform laser-directed energy deposition additive manufacturing on the pretreated metal substrate surface; Also includes: S4. Perform a second heat treatment on the workpiece obtained by laser-directed energy deposition additive manufacturing to improve the thermal conductivity of the metal substrate.

2. The method according to claim 1, characterized in that, In S1, after the first heat treatment, the following steps are also included: The area to be deposited on the metal substrate is scanned with a laser to induce an over-dissolved state in the area.

3. The method according to claim 1, characterized in that, The first heat treatment includes: solution heat treatment, cold rolling-solution heat treatment, or chemical heat treatment; The second heat treatment includes: aging precipitation heat treatment or annealing heat treatment.

4. The method according to claim 1 or 2, characterized in that, The high thermal conductivity metal matrix is ​​a precipitation-strengthened high thermal conductivity alloy.

5. The method according to claim 4, characterized in that, The precipitation-strengthened high thermal conductivity alloy includes copper alloys or aluminum alloys.

6. The method according to claim 1 or 2, characterized in that, The manufacturing methods of the high thermal conductivity metal matrix include: casting, forging, rolling, laser powder bed manufacturing, electron beam powder bed manufacturing, laser filament forming, or electric arc filament forming.

7. A bimetallic component, characterized in that, It is prepared by the method described in any one of claims 1-6.

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