A method for forming a porous metal part by selective laser melting with interrupted scanning

Abstract

The application belongs to the technical field of laser additive manufacturing, and discloses a discontinuous scanning laser selective melting forming method for a porous metal part, which comprises the following steps: layering and slicing a three-dimensional model of the porous metal part to be formed according to a preset layer thickness; filling each layer slice in sequence by using a discontinuous laser scanning track to obtain laser discontinuous scanning track filling data, wherein the discontinuous laser scanning track is arranged as follows: the discontinuous laser scanning tracks in the same layer slice are parallel to each other, and the discontinuous laser scanning tracks in the odd layer slices and the even layer slices form a preset included angle; the laser scanning track is composed of a solid scanning track and a spacing track, and the solid scanning track and the spacing track are arranged alternately and linearly; and laser selective melting forming is performed based on the preset layer thickness and the laser discontinuous scanning track filling data to obtain the porous metal part. The application simplifies the preparation process of the porous metal part, and can prepare a metal part with high porosity, high pore uniformity and high pore connectivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of laser additive manufacturing, and more particularly, to an intermittent scanning type laser selective melting forming method of a porous metal part. BACKGROUND

[0002] Porous metal parts have the advantages of low density and large specific surface area, and are widely used in the fields of aerospace, automobile manufacturing, energy, biomedicine, construction, electronics, etc. as functional metal parts. Although the traditional preparation methods of porous metal parts, such as sintering method and foaming method, can meet the production needs of porous metal parts to some extent, they are difficult to realize high-performance and high-efficiency manufacturing of porous metal parts. Selective laser melting (SLM) technology is one of the laser additive manufacturing technologies that have developed very rapidly at present, and has the advantages of wide material adaptability, short manufacturing cycle and strong performance, which provides a new solution for the customized and structure-function integrated production needs of complex porous metal parts. For example, a laser selective melting forming method of a multi-level interconnected micro-porous metal sweating structure is disclosed in Chinese patent application No. CN112935277B, which obtains a first-level micro-pore by simply performing Boolean operation on the original digital model of the part, a second-level micro-pore by setting the interval of the laser scanning track line to be greater than the cladding line width, and a third-level micro-pore by increasing the laser energy input to generate pores at the bottom of the molten pool. Through multi-level micro-pore design, the spatial interconnectivity and uniformity of the pores are enhanced, and to some extent, the problems of single pore direction and anisotropic pore structure are solved. However, this method still relies on the preprocessing of the part model, which not only increases the manufacturing cost, but also reduces the production efficiency.

[0003] In summary, the existing SLM forming methods of porous metal parts are difficult to meet the needs of high-efficiency and high-performance forming of porous metal parts with controllable pore structure and interconnected and isotropic pores without changing the original digital model of the metal part. SUMMARY

[0004] In view of the defects of the prior art, the purpose of the present application is to provide an intermittent scanning type laser selective melting forming method of a porous metal part, which aims to solve the problem that the existing SLM forming methods of porous metal parts cannot meet the manufacturing needs of porous metal parts with simplified model design, reduced model data volume, adjustable pore structure, uniform pore distribution and interconnected pores.

[0005] To achieve the above-mentioned purpose, the present application provides an intermittent scanning type laser selective melting forming method of a porous metal part, which comprises:

[0006] S1 divides a three-dimensional model of a to-be-formed porous metal part into layers according to a preset layer thickness to obtain a plurality of layers of slices;

[0007] S2 fills each layer of slice in sequence by using an intermittent laser scanning track to obtain laser intermittent scanning track filling data, wherein the intermittent laser scanning track is arranged to be parallel to each other in the same layer of slice, and the intermittent laser scanning track in the odd layer of slice forms a preset angle with the intermittent laser scanning track in the even layer of slice; the laser scanning track is composed of a solid scanning track and an interval track, and the solid scanning track and the interval track are arranged alternately and linearly.

[0008] S3 performs laser selective melting forming based on the preset layer thickness and the laser intermittent scanning track filling data, and in the forming process, laser melting forming is performed on the solid scanning track, and laser melting forming is stopped at the interval track to obtain a porous metal part.

[0009] The above forming method provided in the application realizes complete connection of pores in the laser selective melting forming process of the porous metal part layer by layer and pass by pass, greatly improves the porosity, uniformity of pore distribution and pore connectivity of the metal part, and effectively improves the anisotropy of the metal part. At the same time, the manufacturing cycle of the porous metal part is shortened, the production process is simplified, and the production cost of the porous metal part is greatly reduced.

[0010] Further, in step S2, the length of the solid scanning track is 0.1mm-5mm, and the length of the interval track is 0.05mm-2.5mm.

[0011] Further, the length of the interval track and the length of the solid scanning track are located between 0.1-0.5.

[0012] Further, in step S2, the laser moving speed at the interval track is greater than the laser scanning speed at the solid scanning track.

[0013] Further, the laser moving speed at the interval track is located in the range of 1000mm / s-6000mm / s, and the laser scanning speed at the solid scanning track is located in the range of 300mm / s-2000mm / s.

[0014] Further, in step S2, in the same layer of slice, the interval between adjacent intermittent laser scanning tracks is greater than the width of the laser melt pool formed by the laser scanning track; and / or, the interval between adjacent intermittent laser scanning tracks is 1-5 times the width of the laser melt pool.

[0015] Further, in step S3, when printing layer by layer, the laser galvanometer motor is used to rotate to control the laser scanning trajectory in the odd layer slice and the laser scanning trajectory in the even layer slice to form an included angle, and the included angle satisfies: 0° < ω < 180°.

[0016] Further, the included angle between the laser scanning trajectories between the odd layer and the even layer is an integer multiple of 180°.

[0017] Further, in step S1, the preset layer thickness is 0.02mm-0.4mm.

[0018] Further, in step S1, when the porosity requirements of different sections on the to-be-formed porous metal part are different, the porous metal part is segmented according to different porosities; and in the corresponding step S2, in different sections, the length of the solid scanning trajectory and / or the length of the interval trajectory of the intermittent laser scanning trajectory in each layer slice are different.

[0019] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0020] 1. The intermittent scanning laser selective melting forming method of the porous metal part provided by the present application does not need to perform additional processing on the original three-dimensional digital model of the metal part, that is, the three-dimensional digital model of the porous metal part can be designed according to the solid shape, without the need to design the porosity structure, which greatly reduces the design difficulty of the three-dimensional digital model of the porous metal part and significantly reduces the data amount of the three-dimensional digital model. Through the intermittent scanning laser selective melting forming method, the porous metal part can be manufactured, the preparation process is highly simplified, and the preparation process meets the high-efficiency and high-quality forming requirements of the porous metal part.

[0021] 2. The intermittent scanning laser selective melting forming method provided by the present application designs an intermittent scanning laser trajectory, in which the solid scanning trajectory and the interval trajectory are alternately arranged in a straight line. In actual preparation of the porous metal part, laser scanning and melting are performed at the solid scanning trajectory, and laser scanning is stopped at the interval trajectory, so that a metal structure with porosity in each layer can be obtained, and the complete connection of the porosity in the preparation process of the porous metal part is realized, the porosity and the uniformity of the porosity distribution are greatly improved, the anisotropy is effectively improved, and the like.

[0022] 3. The intermittent scanning laser selective melting forming method provided by the present application not only shortens the manufacturing cycle of the porous metal part, simplifies the production process, but also greatly reduces the production cost of the porous metal part.

[0023] 4. The interrupted scanning laser selective melting forming method provided by the application can control the porosity and pore structure of the porous metal part by changing the length of the solid scanning track and the interval track in the interrupted parameter of the laser track line, which is simple to operate.

[0024] 5. The interrupted scanning laser selective melting forming method provided by the application can also realize the gradient change of the porosity by controlling the length of the solid scanning track and the interval track in the laser interrupted scanning track line of different slice layers in different sections when the porosity requirements of different sections of the same part are different, and manufacture the porous metal part with gradient change of the porosity. In summary, the interrupted scanning laser selective melting forming method provided by the application can simplify the preparation process of the gradient porous metal part, increase the design freedom of the porous metal part, and provide a new solution for the integrated manufacturing of the porous metal part. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a process schematic diagram of the interrupted scanning laser selective melting forming method of the porous metal part provided by the application;

[0026] Figure 2 is a schematic diagram of the traditional continuous scanning laser scanning track line and the corresponding melt channel structure provided by the application;

[0027] Figure 3 is a schematic diagram of the interrupted laser scanning track line and the corresponding melt channel structure provided by the application;

[0028] Figure 4 is a schematic diagram of the length of the solid track and the interval track of the interrupted laser scanning track line and the corresponding melt channel provided by the application;

[0029] Figure 5 is a schematic diagram of the traditional continuous scanning laser scanning melt channel filling effect and the interrupted laser scanning melt channel filling effect based on the 90° interlayer angle provided by the application;

[0030] Figure 6 is a schematic diagram of the interrupted laser scanning track line of the titanium alloy porous gradient metal flat plate part provided by embodiment 3 of the application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as there is no conflict.

[0032] The application provides a discontinuous scanning laser selective melting forming method for a porous metal part, as shown in the accompanying drawings. Figure 1 The forming method comprises the following steps:

[0033] S1: importing a three-dimensional digital model of the porous metal part into a laser selective melting device, slicing the three-dimensional digital model of the porous metal part to be formed according to a preset layer thickness, and obtaining a plurality of layers of slices;

[0034] S2: filling each layer of slice with a discontinuous laser scanning track in sequence to obtain laser discontinuous scanning track filling data, wherein the discontinuous laser scanning track is set as follows: the discontinuous laser scanning tracks in the same layer of slice are parallel to each other, and the discontinuous laser scanning tracks in the odd layer of slice and the even layer of slice form a preset included angle; the laser scanning track is composed of a solid scanning track and a spacing track, and the solid scanning track and the spacing track are arranged alternately and linearly.

[0035] S3: performing laser selective melting forming based on the preset layer thickness and the laser discontinuous scanning track filling data, and performing laser melting forming on the solid scanning track and stopping laser melting forming at the spacing track in the forming process to obtain the porous metal part.

[0036] In step S1, the three-dimensional digital model of the porous metal part is first imported into the laser selective melting device, the three-dimensional digital model is sliced according to the preset layer thickness, and the layer-by-layer cross-sectional profile of the three-dimensional digital model is obtained from bottom to top; in the application, the original model of the three-dimensional digital model of the porous metal part can be designed as a solid model, and there is no need to design a pore structure additionally, so that the data amount of the three-dimensional digital model is significantly reduced.

[0037] In step S2, the discontinuous laser scanning track is used to fill each layer of slice in sequence, and the discontinuous laser scanning track is specifically set as follows:

[0038] 1) in the same layer of slice, the discontinuous laser scanning tracks are parallel to each other, and the line spacing of the adjacent two laser scanning tracks is greater than the width of the laser melt track formed after laser melting along any one laser scanning track, so as to ensure that the adjacent laser melt tracks do not contact, thereby forming an initial pore. The laser melt track refers to a melting track formed by laser melting metal powder bed along the laser scanning track, and the width of the laser melt track is related to the powder material, the preset layer thickness, the laser power and other laser processing parameters, and the value of the laser melt track width can be obtained through a large number of basic process test historical data. The line spacing of the laser scanning track refers to the distance between the center axes of the adjacent two laser scanning tracks in the same layer of slice.

[0039] Specifically, the spacing between adjacent intermittent laser scanning trajectories within the same slice layer is selected within the range of 1-5 times the width of the laser melt channel. For example, the spacing between adjacent intermittent laser scanning trajectories can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 times the width of the laser melt channel, or any multiple between any two of these multiples, to ensure that adjacent laser melt channels do not contact each other and can generate initial porosity. The spacing between adjacent intermittent laser scanning trajectories selected according to this principle is easier to calculate and has more regular values, which helps improve the stability and reliability of the forming process, thereby improving the forming quality of porous metal parts. While ensuring that adjacent melt channels do not contact each other, the multiple can be adjusted as needed. A larger multiple results in a larger initial porosity and a correspondingly higher porosity.

[0040] 2) Ensure that the projections of the intermittent laser scanning trajectories within odd-numbered and even-numbered layers intersect on the XY horizontal plane, meaning that the intermittent laser scanning trajectories between adjacent layers form a preset angle. The preset angle is greater than 0° and less than 180°. This is because in some laser selective melting equipment, the angle between adjacent layers is adjusted by rotating the laser galvanometer motor. Within this rotation angle range, the laser galvanometer motor can drive the laser emitter to rotate, allowing the intermittent laser scanning trajectory to cover the entire contour area of ​​the porous metal part, thereby achieving uniform melting and deposition of the metal powder. If the angle between adjacent layers exceeds this range, it may increase the complexity of the software-controlled motor and also affect the stability and reliability of the laser selective melting equipment, leading to repetition or omission of laser scanning trajectories.

[0041] In a more preferred embodiment, the angle between the laser scanning trajectories of odd-numbered and even-numbered layers is divisible by 180°, such as 30°, 45°, 60°, 90°, etc. During the laser selective melting process, residual stress is generated inside the metal part due to rapid heating and cooling. Selecting an angle divisible by 180° between adjacent layers makes it easier to control the rotation angle of the motor, makes the distribution of the laser scanning trajectory lines between different layers more uniform, helps to reduce the accumulation of residual stress, and improves the forming quality of porous metal parts.

[0042] 3) such as Figure 2 As shown, the traditional continuous laser scanning trajectory A and its corresponding melting channel B are both a single straight line segment. Figure 3 As shown, the intermittent laser scanning trajectory provided in this application a Then the solid line scan trajectory a1 and the interval trajectory located between two adjacent solid line scan trajectories. a2 Alternating composition, and solid line scanning trajectory a1 and interval trajectory a2The length is adjustable; the laser scans only along the solid line trajectory. a1 Internal scanning of molten metal powder, while in the interval trajectory a2 The internal scanning and melting process is stopped, resulting in the interval trajectory. a2 Finally, interconnected channels of the initial pores are formed, corresponding to the melt channels. b It is also intermittent, containing solid melt lines. b1 and interval melt channel b2 .

[0043] Specifically, such as Figure 4 As shown, the solid line scan trajectory length *m* refers to the length of a single laser-affected trajectory line, and the interval trajectory length *n* refers to the length of a single laser-free trajectory line. Specifically, the solid line scan trajectory... a1 The length m is 0.1mm~5mm, and the interval trajectory is... a2 The length n is 0.05mm~2.5mm, and the interval trajectory a2 The length n of the solid line scan trajectory a1 The ratio of n / m to the length m is between 0.1 and 0.5. When the ratio of n / m is less than 0.10, the laser interval trajectory length is too short to form a stable interconnection channel; when the ratio of n / m is greater than 0.50, the laser interval trajectory length n will be greater than the solid line scanning trajectory length m. At this time, the solid line melt channel b1 will not be sufficient to maintain the stable forming of porous metal parts.

[0044] In step S2, the laser speed at the solid line scanning trajectory and the interval trajectory is also set so that the laser moving speed at the interval trajectory is greater than the laser scanning speed at the solid line scanning trajectory. The purpose is to reduce the time without laser action within the interval trajectory, thereby improving production efficiency and reducing costs.

[0045] Specifically, the scanning speed at the solid line scanning trajectory refers to the actual scanning speed when the laser scans the solid line scanning trajectory, while the laser movement speed at the interval trajectory refers to the speed at which the laser moves from the end of the previous solid line scanning trajectory through the interval trajectory to the beginning of the next solid line scanning trajectory. More specifically, the laser movement speed at the interval trajectory is set to be within the range of 1000mm / s to 6000mm / s, such as 1000mm / s, 2000mm / s, 3000mm / s, 4000mm / s, 5000mm / s, 6000mm / s, or any speed value between any two of the above; the laser scanning speed at the solid line scanning trajectory is set to be within the range of 300mm / s to 2000mm / s, such as 300mm / s, 500mm / s, 700mm / s, 900mm / s, 1000mm / s, 1300mm / s, 1500mm / s, 1800mm / s, 2000mm / s, or any speed value between any two of the above.

[0046] In step S3, the thickness of the single-layer powder bed in the laser selective melting is set as a preset layer thickness, and the preset layer thickness is 0.02 mm-0.4 mm, such as 0.02 mm, 0.05 mm, 0.08 mm, 0.1 mm, 0.13 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.23 mm, 0.25 mm, 0.28 mm, 0.3 mm, 0.35 mm, 0.4 mm, or any value between any two of the above values. If the thickness of the single-layer powder bed is less than 0.02 mm, the forming efficiency is too low; if the thickness of the single-layer powder bed is greater than 0.40 mm, the forming precision is too low.

[0047] In actual layer-by-layer manufacturing by using the laser selective melting process, the metal powder material selected includes commonly used metal additive manufacturing materials such as nickel-based superalloy, titanium alloy, aluminum alloy, cobalt-based alloy, and tungsten-based alloy. In the preparation process, the laser galvanometer motor is rotated to control the laser scanning trajectories in the odd layer slice and the even layer slice to form an included angle, and the included angle satisfies: 0°< ω < 180°.

[0048] In other preferred embodiments, in step S1, when the porosities of different sections on the porous metal part to be formed are different, the porous metal part is segmented according to different porosities; in the corresponding step S2, in different sections, the length of the solid scanning trajectory and / or the length of the interval trajectory constituting the intermittent laser scanning trajectory in each layer slice are different.

[0049] The specific implementation method of different porosities is as follows:

[0050] ① Whole porous metal part porosity control method: the same solid scanning trajectory length and interval trajectory length are set for all the slice layers, and adjusting the solid scanning trajectory length and the interval trajectory length can realize the whole control of the internal porosity characteristics of the porous metal part.

[0051] ② Porous metal part porosity gradient control method: according to the actual porosity requirement, the slice layers of the three-dimensional model of the porous metal part are segmented, different solid scanning trajectory lengths and interval trajectory lengths are set for the slice layers of different sections, or different solid scanning trajectory lengths and the same interval trajectory lengths are set for the slice layers of different sections, or the same solid scanning trajectory lengths and different interval trajectory lengths are set for the slice layers of different sections, so as to realize the gradient setting of the porosity characteristics of the porous metal part through the combination of the solid scanning trajectory and the interval trajectory of multiple lengths.

[0052] The following describes the intermittent scanning laser selective melting forming method of the porous metal part provided above through multiple embodiments.

[0053] Embodiment 1

[0054] The present embodiment takes a GH4169 nickel-based superalloy porous test block as an example, which has a size of 10 mm x 10 mm x 10 mm. The specific steps of the forming method of the GH4169 nickel-based superalloy porous test block are as follows:

[0055] (1) Import the three-dimensional digital model (hereinafter referred to as three-dimensional model) of the nickel-based superalloy porous test block into the laser selective melting equipment; slice the three-dimensional model according to a preset layer thickness of 0.05 mm to obtain the layer-by-layer cross-sectional profile of the three-dimensional model from bottom to top, and each layer-by-layer cross-sectional profile is a square with a size of 10 mm x 10 mm. The three-dimensional digital model of the aforementioned nickel-based superalloy porous test block only contains the outer dimensions of the solid test block, and the internal pore structure is not designed.

[0056] (2) Fill the multi-layer slice cross-section with an intermittent laser scanning track layer by layer. The related parameters of the intermittent laser scanning track are set as follows:

[0057] ① In the same layer cross-section, the intermittent laser scanning track is set to be parallel to each other; according to the basic process test, it is confirmed that the laser melt width of GH4169 nickel-based superalloy under the condition of laser power of 300 W is 100 μm; accordingly, the distance between adjacent laser scanning tracks is set to be 1.5 times the melt width, i.e. the distance between adjacent laser scanning tracks is 150 μm, so as to ensure that the adjacent laser melt does not contact, thereby forming the initial pores.

[0058] ② The intermittent laser scanning track is composed of solid scanning tracks and interval tracks alternately arranged to form a linear track; specifically, the length of the solid scanning track m = 1.00 mm, the length of the interval track n = 0.20 mm, the ratio of the length of the interval track to the length of the solid track is 0.2, the laser scanning speed of the solid scanning track segment is set to 1000 mm / s, and the moving speed of the laser skipping the interval track segment is set to 3000 mm / s; so that the laser only works in the solid scanning track segment, and does not work in the interval track segment, so that the interval track segment does not have a melt, thereby forming the interconnected channels of the initial pores;

[0059] ③ The angle between the intermittent laser scanning tracks of the adjacent two layers (i.e. the angle between the adjacent layers) is selected to be 90°.

[0060] All slice cross-sectional profiles are filled layer by layer from bottom to top by using the intermittent laser scanning track set in step (2) to generate a laser intermittent scanning filling file that can be recognized by the laser selective melting equipment. Specifically, the laser scanning filling file of each layer is combined to obtain complete laser intermittent scanning filling data containing the laser scanning filling information of all slice layers.

[0061] (3) Put the dried GH4169 nickel-based superalloy metal powder into the laser selective melting equipment, and complete the laser selective melting forming of the superalloy porous test block from bottom to top layer by layer and pass by pass according to the preset layer thickness of 0.05 mm in step (1) and the complete laser intermittent scanning filling file obtained in step (2); during the forming process, the laser melted metal powder in the solid scanning track in the intermittent laser scanning track forms a dense pore wall, and the laser is turned off in the interval track to form an interconnected channel between the initial pores. The nickel-based superalloy porous test block with uniform pore distribution and interconnected pores is prepared according to the intermittent scanning laser selective melting forming method, and the internal pore structure is as shown in the right graph of Figure 5 Figure 2, compared with the internal pore structure of the metal plate prepared by the laser selective melting process according to the continuous laser scanning track under the same conditions, as shown in the left graph of Figure 5 Figure 2, it can be seen that the internal porosity of the metal in this embodiment is larger, the pore distribution uniformity is better, and the pore connectivity is stronger.

[0062] Example 2

[0063] This embodiment takes an AlSi10Mg aluminum alloy porous metal flat plate as an example, which has a size of 100 mm x 80 mm x 10 mm. The specific steps of the forming method of the AlSi10Mg aluminum alloy porous metal flat plate are as follows:

[0064] (1) Import the three-dimensional digital model (size: 100 mm x 80 mm x 10 mm, hereinafter referred to as three-dimensional model) of the AlSi10Mg aluminum alloy porous metal flat plate metal part into the laser selective melting equipment; layer the three-dimensional model according to the preset layer thickness of 0.02 mm, and obtain the cross section profile of the three-dimensional model layer by layer from bottom to top. The cross section profile is a rectangle with a size of 80 mm x 10 mm. The three-dimensional model of the aluminum alloy porous metal flat plate is designed according to the outer dimensions of the solid flat plate, and does not need to be designed with additional pore structure.

[0065] (2) Fill the multi-layer slice cross section layer by layer with the preset intermittent laser scanning track line. The related parameters of the intermittent laser scanning track are set as follows:

[0066] ① In the same layer cross section, the intermittent laser scanning track line is set to be parallel to each other; according to the basic process test, it is confirmed that the AlSi10Mg aluminum alloy laser melt width under the condition of laser power of 400 W is 150 μm; accordingly, the distance between adjacent intermittent laser scanning track lines is set to be 2.0 times the melt width, i.e. the distance between adjacent intermittent laser scanning track lines is 300 μm, so as to ensure that the adjacent melt tracks do not contact, thereby forming initial pores;

[0067] ② The intermittent laser scanning trajectory is composed of solid scanning trajectories and interval trajectories arranged alternately in a linear trajectory. Specifically, the length of the solid scanning trajectory is m = 2.00 mm, the length of the interval trajectory is n = 0.50 mm, the ratio of the length of the interval trajectory to the length of the solid trajectory is 0.25, the laser scanning speed of the solid scanning trajectory segment is set to 1400 mm / s, and the moving speed of the laser skipping the interval trajectory segment is set to 4000 mm / s; the laser only works in the solid scanning trajectory segment, and does not work in the interval trajectory segment, so that the interval trajectory segment does not have a molten channel, thereby forming an interconnected channel of the initial pores;

[0068] ③ The included angle of the intermittent laser scanning trajectory between the adjacent two layers (i.e., the interlayer angle) is selected to be 60°.

[0069] The intermittent laser scanning trajectory set in step (2) fills all the slice cross-sectional profiles from bottom to top layer by layer to generate a laser intermittent scanning filling file that can be recognized by a laser selective melting device. Specifically, the laser scanning filling file of each layer is combined to obtain complete laser intermittent scanning filling data containing all the slice layer laser scanning filling information.

[0070] (3) The dried AlSi10Mg aluminum alloy metal powder is loaded into the laser selective melting device, and the laser selective melting forming of the aluminum alloy porous metal plate is completed from bottom to top layer by layer according to the preset layer thickness of 0.02 mm in step (1) and the complete laser intermittent scanning filling file generated in step (2). During the forming process, the laser melts the metal powder in the solid scanning trajectory of the intermittent laser scanning trajectory to form a dense pore wall, and the laser is turned off in the interval trajectory to form an interconnected channel between the initial pores. According to the intermittent scanning laser selective melting forming method, a nickel-based high-temperature alloy porous test block with uniform pore distribution and interconnected pores is prepared.

[0071] Example 3

[0072] This example takes a Ti6Al4V titanium alloy porous gradient metal plate part as an example, which has a size of 150 mm x 70 mm x 10 mm. The titanium alloy porous gradient metal plate part requires a porosity along the height direction (total height 150 mm) to set a group of porosity values every 50 mm, a total of three porous plate regions with different porosities, and the three porosity values increase. The specific steps are as follows:

[0073] (1) Import the three-dimensional digital model (150mm×70mm×10mm) of the Ti6Al4V titanium alloy porous gradient metal plate part into the laser selective melting equipment; slice the three-dimensional digital model into layers according to the preset layer thickness of 0.04mm, so as to obtain the layer-by-layer cross-sectional contour of the three-dimensional digital model from bottom to top. The layer-by-layer cross-sectional contour is rectangular (70mm×10mm). According to the porosity requirements of the titanium alloy porous gradient metal plate, the sliced ​​layers of the porous gradient plate are divided into three segments from bottom to top according to the height range of 0-150mm, that is, the layer number range of 1-3750. Figure 6 As shown:

[0074] Section 1: Height range 0-50mm, number of layers range 1-1250;

[0075] Second section: Height range 50-100mm, number of floors range 1251-2500;

[0076] Third section: 100-150mm, number of layers ranges from 2501 to 3750;

[0077] The original model of the Ti6Al4V titanium alloy porous gradient metal plate was designed based on the shape information of the solid plate, without additional design of the pore structure inside.

[0078] (2) Intermittent laser scanning trajectory lines are used to fill multiple slice sections layer by layer. The relevant parameters of the intermittent laser scanning trajectory are set as follows:

[0079] ① Within the same cross-section, the intermittent laser scanning trajectory lines are set to be parallel to each other; based on the basic process test, it is confirmed that the width of the laser melting channel of Ti6Al4V titanium alloy under the laser power of 280W is 110μm; correspondingly, the spacing between adjacent intermittent laser scanning trajectory lines is set to 2.5 times the width of the melting channel, that is, the spacing between intermittent laser scanning trajectory lines is 275μm, to ensure that adjacent melting channels do not contact each other, thereby forming an initial porosity;

[0080] ② The intermittent laser scanning trajectory is a linear trajectory composed of alternating solid scanning trajectories and interval trajectories; specifically, the laser only works in the solid scanning trajectory segment, while it does not work in the interval trajectory segment, so that there will be no melting channel in the interval trajectory segment, thus forming the interconnection channel of the initial pores.

[0081] ③ The angle between adjacent floors is selected as 60°.

[0082] ④ Because the porous gradient plate of this titanium alloy requires the porosity to be distributed in an equally spaced gradient along the length direction, the length of the solid line scanning trajectory and the length of the interval trajectory are gradient-set within the three-segment slice layering range of the porous gradient plate, combined with... Figure 6 As shown, the specific settings are as follows:

[0083] The first section: 0-50mm, the number of layers ranges from 1 to 1250, the length of the solid scanning track m1 is set to 2.00mm, and the length of the interval track n1 is set to 0.30mm. Under the value of the parameters, the ratio of the length of the interval track to the length of the solid scanning track is 0.15.

[0084] The second section: 50-100mm, the number of layers ranges from 1251 to 2500, the length of the solid scanning track m2 is set to 2.00mm, and the length of the interval track n2 is set to 0.40mm. Under the value of the parameters, the ratio of the length of the interval track to the length of the solid scanning track is 0.20.

[0085] The third section: 100-150mm, the number of layers ranges from 2501 to 3750, the length of the solid scanning track m3 is set to 2.00mm, and the length of the interval track n3 is set to 0.50mm. Under the value of the parameters, the ratio of the length of the interval track to the length of the solid scanning track is 0.25.

[0086] The gradient of the length of the solid scanning track and the length of the interval track in the above three sections meets the stable forming requirements of the Ti6Al4V titanium alloy porous gradient flat plate metal part. From bottom to top, the ratio of the length of the interval track to the length of the solid scanning track in the three sections is 0.15, 0.20 and 0.25 respectively, and the porosity gradient increases.

[0087] After filling the corresponding slice cross-section profile with the discontinuous laser scanning track line set according to the foregoing, the laser scanning filling files generated layer by layer are merged to obtain a complete laser discontinuous scanning filling file containing the laser scanning filling file information of all slice layers.

[0088] (3) The dried Ti6Al4V titanium alloy metal powder is loaded into a laser selective melting device, and the laser selective melting forming of the Ti6Al4V titanium alloy gradient porous flat plate metal part is completed layer by layer and pass by pass from bottom to top according to the preset layer thickness 0.04mm in step (1) and the complete laser discontinuous scanning filling file obtained in step (2). During the forming process, in the laser discontinuous scanning track, the laser melts the metal powder in the solid scanning track to form a dense pore wall, and the laser is turned off in the interval track, thereby forming interconnected channels between the initial pores. After the laser selective melting forming by layer and pass by pass, the Ti6Al4V titanium alloy gradient porous flat plate metal part with uniform pore gradient distribution and interconnected pores is obtained.

[0089] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for intermittent scanning laser selective melting forming of porous metal parts, characterized in that, The forming method includes: S1 slices the three-dimensional digital model of the porous metal part to be formed into layers according to the preset layer thickness to obtain multi-layer slices; S2 uses intermittent laser scanning trajectories to sequentially fill each slice layer, obtaining intermittent laser scanning trajectory filling data. The intermittent laser scanning trajectories are set as follows: the intermittent laser scanning trajectories within the same slice layer are parallel to each other, and the intermittent laser scanning trajectories within odd-numbered slice layers and even-numbered slice layers form a preset angle. The laser scanning trajectory consists of solid line scanning trajectories and interval trajectories, which alternate and are arranged in a straight line. The interval trajectories represent areas without laser interaction. S3 performs laser selective melting and forming based on the preset layer thickness and the laser intermittent scanning trajectory filling data. During the forming process, laser melting and forming is performed on the solid line scanning trajectory, and laser melting and forming is stopped at the interval trajectory to obtain a porous metal part.

2. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S2, the length of the solid line scanning trajectory is 0.1mm to 5mm, and the length of the interval trajectory is 0.05mm to 2.5mm.

3. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 2, characterized in that, The ratio of the length of the interval trajectory to the length of the solid line scan trajectory is between 0.1 and 0.

5.

4. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S2, the laser moving speed at the interval trajectory is greater than the laser scanning speed at the solid line scanning trajectory.

5. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 4, characterized in that, The laser moving speed at the interval trajectory is in the range of 1000mm / s to 6000mm / s; the laser scanning speed at the solid line scanning trajectory is in the range of 300mm / s to 2000mm / s.

6. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S2, within the same slice layer, the spacing between adjacent intermittent laser scanning trajectories is greater than the width of the laser melting channel formed by the corresponding laser scanning trajectory; and / or, the spacing between adjacent intermittent laser scanning trajectories is 1 to 5 times the width of the laser melting channel.

7. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S3, during layer-by-layer printing, the laser galvanometer motor is used to rotate and control the laser scanning trajectories in odd-numbered slices and even-numbered slices to form an angle, and the angle satisfies: 0° < ω < 180°.

8. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 7, characterized in that, The angle between the laser scanning trajectories of odd-numbered and even-numbered layers is divisible by 180°.

9. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S1, the preset layer thickness is 0.02mm~0.4mm.

10. The intermittent scanning laser selective melting forming method for porous metal parts as described in claim 1, characterized in that, In step S1, when the porosity requirements of different segments on the porous metal part to be formed are different, the porous metal part segments are sliced ​​according to different porosities; in the corresponding step S2, the length of the solid line scanning trajectory and / or the length of the interval trajectory that constitute the discontinuous laser scanning trajectory in each slice in different segments are different.

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