Process method for forming high-density 98w alloy with high specific gravity by dual laser following printing additive manufacturing technology

Abstract

The application discloses a process method for forming high-density and high-specific-gravity 98W alloy by using a double-laser following printing additive manufacturing technology, and the method is characterized in that: first and second laser beams are used to print nano-modified 98W alloy powder, so as to form high-density and high-specific-gravity 98W alloy; in the nano-modified 98W alloy powder, the weight parts of each component are as follows: W: 98, Ni: 1.4, and Fe: 0.6; in the printing process, the process parameters matched for the first laser beam are consistent with the process parameters matched for the second laser beam, and the value range of the laser bulk energy density E of the first laser beam and the second laser beam is between 450 J / mm 3 1000 J / mm 3 , and the value range of the laser power of the first laser beam and the second laser beam is 180 W-240 W, and the value range of the interval time t is 0.08 s-0.3 s. The application improves the manufacturing precision, improves the material performance, and realizes high-quality and high-performance component manufacturing.

Description

Technical Field

[0001] This invention relates to a process for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology, belonging to the field of laser additive manufacturing. Background Technology

[0002] Tungsten (W) materials, due to their unique properties such as high melting point, high strength, and radiation resistance, are widely used in extreme service environments, including those with high temperatures and strong radiation. The high melting point, high density, and high strength of tungsten and its alloys make them widely applicable in demanding environments, such as rocket engine nozzle throat lining materials and kinetic energy penetrator materials. Traditionally, low-melting-point metals such as Ni, Fe, and Cu are added to the W matrix to synthesize new alloys, namely high-density W alloys (WHAs). Traditional methods for preparing tungsten and its alloys often employ powder metallurgy (PM), spark plasma sintering (SPS), hot isostatic pressing (HIP), and powder injection molding (PIM). However, these techniques have limited reaction temperatures, and the resulting tungsten materials often suffer from problems such as high internal porosity, loose microstructure, and uneven composition.

[0003] LPBF technology, also known as Selective Laser Melting (SLM), uses high-energy-density lasers to completely melt metal powder, producing high-density metal components. Metal additive manufacturing involves the rapid interaction between metallic materials and a high-energy heat source. During this process, the metallic material is instantly melted by the high-energy beam and rapidly solidifies within a very short time, undergoing a complex non-equilibrium metallurgical process. In LPBF processing, the interaction between the laser and the metal powder is complex. When the high-energy laser irradiates the surface of the metal powder, the powder absorbs energy and melts, forming a micro-melt pool. As the laser beam moves, the molten material continuously spreads within the pool, forming a melt channel. LPBF involves complex physicochemical metallurgical processes, such as rapid melting and solidification, evaporation, and phase transformation of materials. Additive manufacturing materials encompass traditional polymers, metals, and ceramics, and are continuously developing towards structural, functional, intelligent, and diversified directions, showing broad application prospects in aerospace, biomedicine, nuclear industry, electronic equipment, and automotive manufacturing.

[0004] The LPBF (Liquid Polymerization) process is an extremely non-equilibrium process, where the melting of the powder and the cooling of the melt are completed in a very short time. The large temperature gradient and rapid solidification rate during this process cause the molten pool to shrink, resulting in significant residual thermal stress and even crack formation. Generally, laser processing is the main factor affecting residual stress and leading to cracking. When the laser energy input is high, it easily induces thermal residual stress in the formed component. Compressive stress tends to form at the center of the LPBF formed component, while tensile stress forms at the edges. Deformation and cracking caused by residual stress are common. If the residual stress inside the material exceeds the local yield stress, it will cause warping or deformation; if the residual stress exceeds the local ultimate tensile stress, it will cause cracking of the component. Furthermore, unmelted metal particles and pores during the forming process also increase the likelihood of crack formation. Summary of the Invention

[0005] The purpose of this invention is to provide a process for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology. This method uses dual-laser follow-printing additive manufacturing technology to print specially made high-specific-gravity W-Ni-Fe alloy powder to form high-density, high-specific-gravity 98W alloy components, meeting the needs of multiple fields such as aerospace, automotive, shipbuilding, construction, military, and medical for high-specific-gravity W-content components.

[0006] It improves the manufacturing precision of formed components, enhances material properties, and enables the manufacturing of high-quality, high-performance components.

[0007] To achieve the above-mentioned technical objectives, the present invention will adopt the following technical solution:

[0008] A method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology includes the following steps:

[0009] Step 1: Prepare the printing powder:

[0010] The printing powder is a nano-modified 98W alloy powder, which is made by uniformly mixing metal nanoparticles with tungsten powder as the matrix.

[0011] In the nano-modified 98W alloy powder, the weight part of W is 98-98.5, and the balance is metal nanoparticles;

[0012] The metal nanoparticles are prepared by mixing nano-nickel powder and nano-iron powder in a mass ratio of 7:3.

[0013] Step 2: Dual-laser follow-printing additive manufacturing of components:

[0014] Two laser beams are used to follow the printing powder prepared in step one of the printing process to obtain the corresponding components.

[0015] The two laser beams are referred to as the first laser beam and the second laser beam; the printing spots of the first and second laser beams can both be projected onto the same part of the printing substrate;

[0016] During printing, the first laser beam is activated first and scanned on the powder bed according to its own preset process parameters along the pre-planned printing path. After a preset interval time t, the second laser beam is activated and scanned on the powder bed according to its own preset process parameters along the pre-planned printing path, thereby completing the follow-up printing of the first and second laser beams on the powder bed at an interval time t.

[0017] During the printing process, the process parameters configured for the first laser beam are consistent with those configured for the second laser beam, and the laser volume energy density E of the first and second laser beams ranges from 450 J / mm². 3 -1000J / mm 3 Meanwhile, the laser power of the first laser beam and the second laser beam ranges from 180W to 240W, and the interval time t ranges from 0.08s to 0.3s.

[0018] The process parameters configured for the first laser beam and the process parameters configured for the second laser beam include laser power, scanning speed, scanning spacing, and layer thickness.

[0019] The formula for calculating the energy density E of a laser volume is:

[0020] E = P / vhd;

[0021] In the formula: P represents laser power; v represents scanning speed; h represents scanning spacing; and d represents layer thickness.

[0022] Preferably, in step one, the average particle size of the nano-nickel powder is 125 nm, and the average particle size of the nano-iron powder is 140 nm; the particle size of the nano-modified 98W alloy powder is 5–25 μm, and the sphericity is 0.95.

[0023] Preferably, in step two, the volume energy density E of the first laser beam and the second laser beam is between 525 J / mm². 3 -1000J / mm 3 The interval t ranges from 0.1s.

[0024] Preferably, in step two, the laser power of the first laser beam and the second laser beam is 180W to 240W, the scanning speed is 300mm / s to 500mm / s, the laser spot diameter is 60μm, the scanning spacing is 40μm, and the powder layer thickness is 20μm; a strip scanning strategy is adopted and the layers are rotated 67° to avoid thermal stress concentration.

[0025] Preferably, in step two, the method for obtaining the process parameters of the first laser beam and the second laser beam specifically includes the following steps:

[0026] Step 2.1: Using traditional LPBF technology, print the printing powder prepared in Step 1 under preset single-laser process parameters to obtain several single-laser printed samples; When printing the printing powder prepared in Step 1 using traditional LPBF technology, the preset single-laser process parameters are: laser power of 200W~450W, scanning speed of 200mm / s~600mm / s, laser spot diameter of 70μm, scanning interval of 50μm, and powder layer thickness of 30μm;

[0027] Step 2.2: After grinding and polishing the single laser-printed sample, observe the internal pores and cracks of the single laser-printed sample with an optical microscope and take pictures to record them, so as to obtain the corresponding polished metallographic photos.

[0028] Step 2.3: By comprehensively analyzing and comparing the polished metallographic images of each single laser-printed sample, the polished metallographic images that meet the requirements for internal pores and crack defects are selected.

[0029] Step 2.4: Extract the single-laser process parameters corresponding to the polished metallographic images selected in Step 2.3;

[0030] Step 2.5: Calculate the corresponding laser energy density E1 based on the single laser process parameters extracted in Step 2.4.

[0031] The laser energy density E1 calculated in steps 2.6 and 2.5 can be used as the reference value for the laser energy density E of the first laser beam and the second laser beam in step two. The laser energy density E and the laser energy density E1 satisfy the following:

[0032] ΔE≤|E-E1|

[0033] ΔE represents the energy offset threshold;

[0034] Step 2.7: Based on the laser energy density E calculated in Step 2.6, preset the process parameters of the first laser beam and the second laser beam, and the value range of each process parameter of the first laser beam and the second laser beam satisfies the following: laser power of 180W~240W, scanning speed of 300mm / s~500mm / s, laser spot diameter of 60μm, scanning spacing of 40μm, and powder layer thickness of 20μm; thereby configuring a series of process parameter arrays for the first laser beam and the second laser beam.

[0035] Step 2.8: Print the printing powder prepared in Step 1 one by one according to the process parameter array set in Step 2.7 to obtain several dual-laser printed samples.

[0036] Step 2.9: After polishing the dual-laser printed sample, observe the internal pores and cracks of the dual-laser printed sample with an optical microscope and take pictures to record them, so as to obtain the corresponding polished metallographic photos.

[0037] Step 2.10: By comprehensively analyzing and comparing the polished metallographic images of each dual-laser printed sample, the polished metallographic images that meet the requirements for internal pores and crack defects are selected.

[0038] Step 2.11: Extract the process parameters corresponding to the polished metallographic photos selected in Step 2.10.

[0039] Preferably, in step two, both laser beams are Gaussian beams, and during the process of dual-laser follow-printing additive manufacturing of the component, the heat energy distribution of the composite heat source formed by the superposition of the two laser beams in space is fitted to the following dual-laser Gaussian surface heat source function:

[0040]

[0041] Where: q h (x,y) represents the Gaussian surface heat source function of the two lasers, and (x,y) represents the spatial position of the composite heat source formed by the superposition of the two laser beams; η is the laser absorptivity, and P... i Let r be the power of the i-th laser beam. i Let be the radius of the i-th laser beam; The position of the i-th laser beam is calculated using the scanning speed v and the interval time t:

[0042]

[0043] in D is the time when the i-th laser beam starts operating. h Where L is the scan spacing and L is the length of a single scan path. χ is the floor function; iχ is a parameter used to control the direction of the i-th laser beam when the two laser beams employ a parallel scanning strategy. i =1; When two laser beams employ a zigzag scanning strategy, the parameter is...

[0044] Preferably, the size deviation of the printing spot of the first and second laser beams is controlled within ±5μm.

[0045] Preferably, the laser power deviation between the first and second laser beams is controlled within 10W.

[0046] Based on the above-mentioned technical objectives, the present invention has the following advantages compared with the prior art:

[0047] 1. Based on the characteristics of tungsten powder, this invention uses tungsten powder as a matrix and mixes in measured amounts of nano-nickel powder and nano-iron powder to prepare nano-modified 98W alloy powder. The nano-nickel powder and nano-iron powder can act as nucleating agents in the solidification process, hinder grain growth, improve grain boundary strength, and suppress the formation of defects such as pores and cracks.

[0048] 2. This invention uses dual-laser follow-print additive manufacturing technology to print the prepared nano-modified 98W alloy powder, and sets corresponding process parameters for the first and second laser beams to form high-density, high-specific-gravity 98W alloy components.

[0049] 3. To obtain the process parameters of the first and second laser beams, this invention uses the single-laser process parameters of the traditional LPBF molding process for forming nano-modified 98W alloy powder as a basis to calculate the corresponding laser energy density. Using this laser energy density as a reference, the laser energy densities of the first and second laser beams are calculated. Simultaneously, considering that the molten pool formed by the first laser beam cannot be completely cooled when the second laser beam is activated, the laser power of the first and second laser beams needs to be limited to prevent overheating of the molten pool formed by the first laser beam during subsequent activation of the second laser beam, which could affect the component forming quality. This constructs a process parameter array consisting of a series of process parameters that meet the requirements. The dual-laser follow-print additive manufacturing technology uses this constructed process parameter array to print the prepared high-density W-Ni-Fe alloy powder to obtain several dual-laser printed components. Based on the evaluation of the defects in the dual-laser printed components, qualified dual-laser printed components are selected, and the corresponding process parameters can then be extracted. Therefore, this invention provides a new approach to configuring process parameters in dual-laser follow-print additive manufacturing technology, making the implementation of dual-laser follow-print additive manufacturing technology a reality.

[0050] 4. By controlling the interval between the two lasers, the Gaussian heat source of the dual lasers can be controlled, affecting the formation of the composite heat source, heat energy distribution, heat conduction effect, and processing effect. This provides an important control method for optimizing laser heating and heat treatment processes. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the overall structure of a dual-laser powder bed melting and forming equipment.

[0052] Figure 2 Image of a sample formed by conventional single-laser powder bed melting;

[0053] Figure 3 Metallographic image of a 98W-Ni-Fe sample formed by conventional LPBF polishing (OM polishing).

[0054] Figure 4 This is a sample of a powder bed molten and formed by dual laser printing with a 0.1-second interval.

[0055] Figure 5 The OM polished metallographic image of a 98W-Ni-Fe sample formed by dual-laser follow-printing additive manufacturing technology (D-LPBF) with a follow-printing interval of 0.1 seconds.

[0056] Figure 6 OM polished metallographic image of a 98W-Ni-Fe sample formed by dual-laser D-LPBF following the printing process at intervals of 0.3 seconds;

[0057] Figure 7 OM polished metallographic image of a 98W-Ni-Fe sample formed by dual-laser D-LPBF following the printing process at 0.5-second intervals;

[0058] Figure 8 The OM polished metallographic image of the 98W-Ni-Fe sample formed by dual-laser D-LPBF following the printing at an interval of 0.08 seconds;

[0059] Figure 9 A comparative histogram of the density of 98W-Ni-Fe samples printed by conventional LBPF and dual-laser D-LPBF at an interval of 0.1 seconds.

[0060] Figure 10 OM metallographic corrosion microstructure of 98W-Ni-Fe sample formed using the optimal traditional LPBF process (400W, 400mm / s);

[0061] Figure 11 The optimal process for dual-laser D-LPBF (interval time 0.1 seconds, 210W, 400mm / s) is used to print the OM metallographic corrosion structure of a 98W-Ni-Fe sample.

[0062] In the diagram: 1-Control system; 21-First laser beam; 22-Second laser beam; 3-Oxygen detector; 4-Powder spreading arm; 5-Forming cylinder. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specifically stated, the relative arrangement, expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of the present invention. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0064] Tungsten alloys with a W content of 98% or more by weight (abbreviated as 98W alloy) have high density, high strength, high temperature resistance, good thermal conductivity, corrosion resistance and wear resistance, superior protective performance, good machinability, and excellent stability, making them suitable for applications in a variety of engineering and technological fields.

[0065] Laser powder bed melting (LPBF) technology can be used to form refractory metal W, but the unavoidable porosity and cracks in the laser processing of pure W have always been important factors restricting pure W as a structural material.

[0066] Low-melting-point metals, such as Ni and Fe nanoparticles, are incorporated into a W matrix to synthesize new alloys, namely high-density W alloys. These metal nanoparticles act as nucleating agents during solidification, hindering grain growth, increasing grain boundary strength, and suppressing the formation of defects such as porosity and cracks. Therefore, a nano-modified high-density 98W alloy was designed. By weight percentage, its components are: W: 98%, Ni: 1.4%, Fe: 0.6%. The average particle size of the nano-nickel powder is 125 nm, the average particle size of the nano-iron powder is 140 nm, the alloy powder has a particle size of 5-25 μm, and a sphericity of 0.95.

[0067] The nano-modified high-density 98W alloy deposited using the conventional LPBF forming process, along with its OM polished metallographic images, can be found in the attached image. Figure 2 , Figure 3 Typically, the specific process parameters for traditional LPBF molding are as follows: laser power of 200W-450W (selectable from 200W, 300W, 350W, 400W, or 450W); scanning speed of 200mm / s-600mm / s (selectable from 200mm / s, 300mm / s, 400mm / s, 500mm / s, or 600mm / s); laser spot diameter of 70μm; scanning spacing of 50μm; powder layer thickness of 30μm; a remelting scanning strategy with 67° interlayer rotation to avoid thermal stress concentration; a 316 stainless steel substrate; and preheating of the substrate by performing three laser scans before molding. Based on the above selectable laser power and scanning speed, several molded samples can be formed, with the sample dimensions being a 10×10×5mm cuboid. (See attached diagram.) Figure 2 .

[0068] After grinding and polishing, the internal pores, cracks, and other defects of each shaped sample were observed using an optical microscope (Olympus Corporation), resulting in corresponding polished metallographic photographs. Figure 3 The polished metallographic images of nine formed specimens with relatively minor structural defects are shown below. The specific process parameters for each specimen are shown in Table 1.

[0069] Table 1. Forming of nano-modified high-density 98W alloy using traditional LPBF forming process.

[0070]

[0071] Based on the appendix Figure 3 The polished metallographic images of the various formed samples show that: 1. When forming nano-modified high-density 98W alloy using the traditional LPBF forming process, the resulting metallographic structure still exhibits significant defects such as cracks and porosity. Therefore, to reduce these defects and improve the performance of the formed components, the traditional LPBF forming process needs to be optimized, providing a new approach to forming nano-modified high-density 98W alloy; 2. The optimal process for forming nano-modified high-density 98W alloy using the traditional LPBF forming process is: laser power of 400W and scanning speed of 400mm / s. This is because, based on the attached... Figure 3 The metallographic images shown indicate that the metallographic structure of the sample deposited by the traditional LPBF forming process at a laser power of 400W and a scanning speed of 400mm / s has the fewest defects.

[0072] Therefore, this invention targets the aforementioned nano-modified high-density 98W alloy and employs dual-laser follow-printing additive manufacturing technology to print high-density, high-density 98W alloy components.

[0073] The challenges in implementing dual-laser follow-print additive manufacturing technology lie in two aspects: firstly, the process parameters configured for each of the two laser beams, and secondly, the interval between the two laser beams in achieving follow-printing.

[0074] This invention addresses the process parameters for forming nano-modified high-density 98W alloy using traditional LPBF molding technology, specifically for configuring the process parameters of dual laser beams in dual-laser follow-printing additive manufacturing technology. The invention includes the following steps:

[0075] Step 2.1: Using traditional LPBF technology, print the printing powder prepared in Step 1 under preset single-laser process parameters to obtain several single-laser printed samples; When printing the printing powder prepared in Step 1 using traditional LPBF technology, the preset single-laser process parameters are: laser power of 200W~450W, scanning speed of 200mm / s~600mm / s, laser spot diameter of 70μm, scanning interval of 50μm, and powder layer thickness of 30μm;

[0076] Step 2.2: After grinding and polishing the single laser-printed sample, observe the internal pores and cracks of the single laser-printed sample with an optical microscope and take pictures to record them, so as to obtain the corresponding polished metallographic photos.

[0077] Step 2.3: By comprehensively analyzing and comparing the polished metallographic images of each single laser-printed sample, select the polished metallographic images that meet the requirements for internal porosity and crack defects. See the attached document for details. Figure 3 ;

[0078] Step 2.4: Extract the single-laser process parameters corresponding to the polished metallographic images selected in Step 2.3. Refer to Table 2 above.

[0079] Step 2.5: Calculate the corresponding laser energy density E1 based on the single laser process parameters extracted in Step 2.4.

[0080] The formula for calculating the laser volume energy density E1 is:

[0081] E1 = P1 / v1*h1*d1;

[0082] In the formula: P1 represents the laser power of the traditional LPBF forming process; v1 represents the scanning speed of the traditional LPBF forming process; h1 represents the scanning spacing of the traditional LPBF forming process; and d1 represents the layer thickness of the traditional LPBF forming process.

[0083] The laser energy density E1 calculated in steps 2.6 and 2.5 can be used as a reference value for the laser energy density E of the first laser beam 21 and the second laser beam 22 in step two. The laser energy density E and the laser energy density E1 satisfy the following:

[0084] ΔE≤|E-E1|

[0085] ΔE represents the energy offset threshold, which is 30 J / mm². 3 ;

[0086] Step 2.7: Based on the laser energy density E calculated in Step 2.6, preset the process parameters of the first laser beam 21 and the second laser beam 22, and the value range of each process parameter of the first laser beam 21 and the second laser beam 22 satisfies the following: laser power is 180W~240W, scanning speed is 300mm / s~500mm / s, laser spot diameter is 60μm, scanning spacing is 40μm, and powder layer thickness is 20μm;

[0087] The formula for calculating the energy density E of a laser volume is:

[0088] E = P / vhd;

[0089] In the formula: P represents laser power; v represents scanning speed; h represents scanning spacing; and d represents layer thickness.

[0090] Based on this, a series of process parameters suitable for dual-laser follow-print additive manufacturing processes can be obtained, as shown in Table 2.

[0091] Specifically, when the present invention uses dual-laser follow-printing additive manufacturing technology to form the above-prepared printing powder, based on the above-mentioned process parameter configuration of the dual laser beams, the corresponding laser energy density E is obtained according to the values ​​corresponding to the energy density E1 of each laser in Table 1. Based on the value range of each process parameter of the first laser beam 21 and the second laser beam 22, the specific process parameter values ​​of the first laser beam 21 and the second laser beam 22 are obtained as shown in Table 2 below:

[0092] Table 2. Process parameters for dual-laser follow-printing additive manufacturing process

[0093]

[0094] Step 2.8: According to the process parameter array set in Step 2.7, print the printing powder prepared in Step 1 one by one to obtain several dual-laser printed samples. The dual-laser printed samples can be referred to the appendix. Figure 4 ;

[0095] Step 2.9: After polishing the dual-laser printed sample, observe the internal pores and cracks of the sample using an optical microscope and take photographs to obtain corresponding polished metallographic images. Refer to the attached document for details. Figure 5-8 ;

[0096] Step 2.10: By comprehensively analyzing and comparing the polished metallographic images of each dual-laser printed sample, the polished metallographic images that meet the requirements for internal pores and crack defects are selected.

[0097] Step 2.11: Extract the process parameters corresponding to the polished metallographic photos selected in Step 2.10.

[0098] Based on the process parameters of the first laser beam 21 and the second laser beam 22 recorded in Table 2, during printing, the first laser beam 21 is first activated and scanned on the powder bed according to the process parameters recorded in Table 2 along the pre-planned printing path. After a preset interval time t, the second laser beam 22 is activated and scanned on the powder bed according to the preset process parameters in Table 2 along the pre-planned printing path, thereby completing the follow-up printing of the first and second laser beams 22 on the powder bed at an interval time t.

[0099] The interval time t takes the values ​​of 0.08s, 0.1s, 0.3s, and 0.5s.

[0100] The first and second laser beams 22 used in this invention are both Gaussian beams. By studying the Gaussian surface heat source function of the dual lasers, the influence of different interval times t on the distribution of the Gaussian surface heat source is investigated, thereby studying the effect of the interval time on the formation of the composite heat source, heat energy distribution, heat conduction effect, and different processing effects on materials. This provides an important control method for optimizing the laser heating process.

[0101] The dual-laser Gaussian surface heat source function is a function fitted based on the thermal energy distribution in space of the composite heat source formed by the superposition of two laser beams during the dual-laser follow-print additive manufacturing process.

[0102] The heat source function of the dual-laser Gaussian surface is as follows:

[0103]

[0104] Where q h (x,y) represents the multi-laser Gaussian surface heat source function, and (x,y) represents the spatial position of the composite heat source formed by the superposition of two laser beams; η is the laser absorptivity, and P... i Let r be the power of the i-th laser beam. iLet be the radius of the i-th laser beam. n represents the number of laser beams. In this invention, two laser beams are used, so n = 2.

[0105] The position of the i-th laser beam is calculated using the scanning speed v and the interval time t:

[0106]

[0107] in D is the time when the i-th laser beam starts operating. h Where L is the scan spacing and L is the length of a single scan path. This is the floor function. χ i Used to control the direction of the beam, the parallel scanning strategy takes χ. i =1, the zigzag scanning strategy is defined as follows:

[0108]

[0109] By controlling the interval between the two lasers, the Gaussian heat source of the dual lasers can be controlled, influencing the formation of the composite heat source, heat energy distribution, heat conduction effect, and processing effect. This provides an important control method for optimizing laser heating and heat treatment processes.

[0110] In equation (2), the interval time t is an important parameter. By controlling the interval time between the two lasers, the Gaussian heat source of the dual lasers can be controlled. In a dual-laser heating system, the interval time between different Gaussian beams can affect the formation and thermal energy distribution of the composite heat source. By adjusting the interval time of different lasers, the superposition effect of the thermal source functions of different Gaussian beams can be controlled. A shorter interval time may lead to a larger overlap of the thermal source functions of the Gaussian beams, forming a more concentrated heat source distribution; while a longer interval time may make the distribution of the thermal source functions relatively dispersed. Therefore, adjusting the interval time can affect the overall thermal energy distribution of the composite heat source. The interval time can also affect the thermal conduction effect of the composite heat source. A shorter interval time may lead to enhanced mutual influence between the thermal source functions of different lasers, accelerating the speed of thermal energy conduction; while a longer interval time may weaken the thermal conduction effect between the thermal source functions. Therefore, by adjusting the interval time, the thermal conduction speed and depth of the composite heat source can be controlled. The control of the interval time can also affect the effect of laser processing. In laser processing and heat treatment, by reasonably adjusting the interval between multiple lasers, different heating and heat treatment effects on materials can be achieved, such as controlling the formation of the molten pool and the size of the heat-affected zone.

[0111] In summary, by controlling the interval between the two lasers, the Gaussian heat source of the dual lasers can be controlled, influencing the formation of the composite heat source, heat energy distribution, heat conduction effect, and processing effect. This provides an important control method for optimizing the laser heating process.

[0112] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0113] Example 1

[0114] Step 1: Prepare the printing powder:

[0115] The printing powder is a nano-modified 98W alloy powder, which is formulated by uniformly mixing nano-nickel powder and nano-iron powder according to a certain amount of tungsten powder as the matrix.

[0116] The components of the nano-modified 98W alloy powder, by weight percentage, are: W: 98%, Ni: 1.4%, Fe: 0.6%.

[0117] The average particle size of the nano-nickel powder is 125 nm, and the average particle size of the nano-iron powder is 140 nm; the particle size of the nano-modified 98W alloy powder is 5–25 μm, and the sphericity is 0.95.

[0118] Step 2: Dual-laser follow-printing powder bed fusion molding process (laser interval time 0.1 seconds):

[0119] A dual-laser powder bed fusion molding system is used, which employs two laser beams to follow the printing powder prepared in step one of the printing process to obtain the corresponding components; the structure of the dual-laser powder bed fusion molding system is as follows: Figure 1 As shown, it includes a control system 1, two laser beams, an oxygen detector 3, a powder spreading arm 4, and a forming cylinder 5.

[0120] The two laser beams are referred to as the first laser beam and the second laser beam 22; the printing spots of the first laser beam and the second laser beam 22 can both be projected onto the same part of the printing substrate;

[0121] During printing, the first laser beam 21 is activated first, and it scans the powder bed according to the pre-planned printing path and the preset process parameters in Table 2. After a preset interval of 0.1 seconds, the second laser beam 22 is activated. The second laser beam begins to melt the powder on the powder bed, connecting with the area printed by the first laser beam. This allows the second laser beam 22 to scan the powder bed according to the pre-planned printing path and the preset process parameters in Table 2, achieving a 0.1-second interval between the first and second laser beams on the powder bed for continuous printing. This process is repeated continuously, switching the laser source at the set interval until the entire model is printed.

[0122] Figure 1 This is a schematic diagram illustrating the principle of the overall structure formed by dual-laser powder bed melting.

[0123] The specific process parameters were as follows: laser power of 180W, 210W, and 240W; scanning speed of 300mm / s, 400mm / s, and 500mm / s, totaling nine parameters. This resulted in the formation of nine block samples, each a 10×10×5mm cuboid. The first and second laser beams had a spot diameter of 70μm and a scanning interval of 40μm. The powder layer thickness was 20μm. A strip-shaped scanning strategy with 67° interlayer rotation was employed to avoid thermal stress concentration. The substrate was 316 stainless steel, and three laser scans were performed before forming to preheat the substrate. This yielded 98W alloy samples formed by D-LPBF follow-printing with a laser interval of 0.1 seconds.

[0124] Example 2

[0125] Step 1: Prepare the printing powder:

[0126] The method is the same as that described in Example 1, and will not be repeated here.

[0127] Step 2: Dual-laser follow-up printing powder bed fusion molding process (laser interval time 0.5 seconds)

[0128] The two laser beams of the dual-laser system are designated as the first and second laser beams 22. The printing spots of both the first and second laser beams 22 can be projected onto the same area of ​​the printing substrate. During printing, the first laser beam 21 is activated first, scanning the powder bed according to its preset process parameters along a pre-planned printing path. After a preset interval t, the second laser beam 22 is activated, scanning the powder bed according to its preset process parameters along the pre-planned printing path. This completes the sequential printing process where the first and second laser beams 22 follow each other on the powder bed at intervals t.

[0129] The specific process parameters are as follows: the laser power of the first and second laser beams are 180W, 210W, and 240W respectively; the scanning speeds are 300mm / s, 400mm / s, and 500mm / s respectively; a total of 3×3, or 9 process parameters, resulting in 9 block samples with a size of 10×10×5mm cuboids. The laser spot diameter of the first and second beams is 70μm, and the scanning interval is 40μm. The powder layer thickness is 20μm. A strip-shaped scanning strategy with 67° interlayer rotation is used to avoid thermal stress concentration. The substrate is a 316 stainless steel substrate, and three laser scans are performed before forming to preheat the substrate. A 98W alloy sample with a laser interval of 0.5 seconds and D-LPBF follow-printing is obtained.

[0130] Example 3

[0131] Step 1: Prepare the printing powder:

[0132] The method is the same as that described in Example 1, and will not be repeated here.

[0133] Step 2: Dual-laser follow-up printing powder bed fusion molding process (laser interval time 0.3 seconds)

[0134] The two laser beams of the dual-laser system are designated as the first and second laser beams 22. The printing spots of both the first and second laser beams 22 can be projected onto the same area of ​​the printing substrate. During printing, the first laser beam 21 is activated first, scanning the powder bed according to its preset process parameters along a pre-planned printing path. After a preset interval t, the second laser beam 22 is activated, scanning the powder bed according to its preset process parameters along the pre-planned printing path. This completes the sequential printing process where the first and second laser beams 22 follow each other on the powder bed at intervals t.

[0135] The specific process parameters are as follows: the laser power of the first and second laser beams are 180W, 210W, and 240W respectively; the scanning speeds are 300mm / s, 400mm / s, and 500mm / s respectively; a total of 3×3, or 9 process parameters, resulting in 9 block samples with a size of 10×10×5mm cuboids. The laser spot diameter of both the first and second laser beams is 70μm, and the scanning interval is 40μm. The powder layer thickness is 20μm. A strip-shaped scanning strategy with 67° interlayer rotation is used to avoid thermal stress concentration. The substrate is 316 stainless steel. Before forming, three laser scans are performed to preheat the substrate. A 98W alloy sample with a laser interval of 0.3 seconds and D-LPBF follow-printing is obtained.

[0136] Example 4

[0137] Step 1: Prepare the printing powder:

[0138] The method is the same as that described in Example 1, and will not be repeated here.

[0139] Step 2: Dual-laser follow-up printing powder bed fusion molding process (laser interval time 0.08 seconds)

[0140] The two laser beams of the dual-laser system are designated as the first and second laser beams 22. The printing spots of both the first and second laser beams 22 can be projected onto the same area of ​​the printing substrate. During printing, the first laser beam 21 is activated first, scanning the powder bed according to its preset process parameters along a pre-planned printing path. After a preset interval t, the second laser beam 22 is activated, scanning the powder bed according to its preset process parameters along the pre-planned printing path. This completes the sequential printing process where the first and second laser beams 22 follow each other on the powder bed at intervals t.

[0141] The specific process parameters are as follows: the laser power of the first and second laser beams are 180W, 210W, and 240W respectively; the scanning speeds are 300mm / s, 400mm / s, and 500mm / s respectively; a total of 3×3, or 9 process parameters, resulting in 9 block samples. The sample size is a cuboid of 10×10×5mm. The diameter of the first and second laser beams is 50μm, and the scanning interval is 40μm. The powder layer thickness is 20μm. A strip scanning strategy is adopted, with interlayer rotation of 67° to avoid thermal stress concentration. The substrate is a 316 stainless steel substrate. Before forming, three laser scans are performed to preheat the substrate. A 98W alloy sample is obtained by D-LPBF follow-printing with a laser interval of 0.08 seconds.

[0142] Experimental Test Example 1: Characterization of LBPF Printed Samples

[0143] After LPBF molding, the molded sample is as follows: Figure 2 As shown. The sample was removed from the substrate using wire electrical discharge machining (EDM), ultrasonically cleaned with anhydrous ethanol, dried, and then subjected to density characterization. Density was measured using Archimedes' displacement method. After polishing, the internal pores, cracks, and other defects of the formed sample were observed using an optical microscope (Olympus Corporation). Metallographic photographs of the polished sample are shown below. Figure 3 As shown.

[0144] Experimental Test Example 2: Characterization of D-LBPF Samples Printed by Dual Laser Follower Printing

[0145] After D-LPBF molding is achieved through dual laser printing with a 0.1-second interval, the molded sample is as follows: Figure 4 As shown. The sample was removed from the substrate using wire electrical discharge machining (EDM), ultrasonically cleaned with anhydrous ethanol, dried, and then subjected to density characterization. Density was measured using Archimedes' displacement method. After polishing, the internal pores, cracks, and other defects of the formed sample were observed using an optical microscope (Olympus Corporation). Metallographic photographs of the polished sample are shown below. Figure 5 As shown.

[0146] Experimental Test Example 3: Characterization of Samples Printed by Dual Lasers at Different Intervals

[0147] The 98W alloy samples printed by dual lasers at different intervals (0.5 seconds, 0.3 seconds, and 0.08 seconds) were tested and characterized using the same testing method as in Experimental Test Example 1.

[0148] Comparing the polished metallographic images of 98W alloys printed by LPBF and D-LPBF at different intervals (0.5 s, 0.3 s, 0.1 s, 0.08 s) along the building direction under the same volumetric energy density and different process parameters, the LPBF-printed 98W alloy exhibits numerous interlayer pores, a loose microstructure, and obvious cracks. In contrast, the D-LPBF-printed samples show almost no pores, a dense and uniform microstructure, and a significant reduction in the number and size of cracks compared to the LPBF-printed samples.

[0149] Comparing the density of 98W samples formed using examples with the same energy density, it was found that the density of samples formed by D-LPBF with a 0.1-second interval was higher than that of samples formed by LPBF. Figure 9 ).

[0150] Experimental Test Example 4: Microstructure Characterization of Printed Samples with LPBF and D-LPBF Intervals of 0.1 Seconds

[0151] The metallographic structure of the formed specimens from the traditional LPBF (400W, 400mm / s) forming process and the D-LPBF 0.1-second interval follow-printing process (210W, 400mm / s) was observed after etching with HF, HNO3, and H2O in a volume ratio of 1:3:7 for 25 seconds. The results are as follows: Figure 10 and 11 As shown, the microstructure of the molded specimens produced by the traditional LPBF (400W, 400mm / s) molding process is mostly equiaxed columnar grains with many long cracks and large grain size; while the microstructure of the molded specimens produced by the D-LPBF 0.1-second interval follow-up printing process (210W, 400mm / s) is mostly fine equiaxed grains, long cracks are broken and greatly reduced, and the grains are significantly refined.

Claims

1. A method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology, characterized in that, Includes the following steps: Step 1: Prepare the printing powder: The printing powder is a nano-modified 98W alloy powder, which is made by uniformly mixing metal nanoparticles with tungsten powder as the matrix. In the nano-modified 98W alloy powder, the weight part of W is 98-98.5, and the balance is metal nanoparticles; The metal nanoparticles are prepared by mixing nano-nickel powder and nano-iron powder in a mass ratio of 7:

3. Step 2: Dual-laser follow-printing additive manufacturing of components: Two laser beams are used to follow the printing powder prepared in step one of the printing process to obtain the corresponding components. The two laser beams are referred to as the first laser beam and the second laser beam; the printing spots of the first and second laser beams can both be projected onto the same part of the printing substrate; During printing, the first laser beam is activated first and scanned on the powder bed according to its own preset process parameters along the pre-planned printing path. After a preset interval time t, the second laser beam is activated and scanned on the powder bed according to its own preset process parameters along the pre-planned printing path, thereby completing the follow-up printing of the first and second laser beams on the powder bed at an interval time t. During the printing process, the process parameters configured for the first laser beam are consistent with those configured for the second laser beam, and the laser volume energy density E of the first and second laser beams ranges from 450 J / mm². 3 -1000J / mm 3 Meanwhile, the laser power of the first laser beam and the second laser beam ranges from 180W to 240W, and the interval time t ranges from 0.08s to 0.3s. The process parameters configured for the first laser beam and the process parameters configured for the second laser beam include laser power, scanning speed, scanning spacing, and layer thickness. The formula for calculating the energy density E of a laser volume is: E = P / vhd; In the formula: P represents laser power; v represents scanning speed; h represents scanning spacing; and d represents layer thickness.

2. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, In step one, the average particle size of the nano-nickel powder is 125 nm, and the average particle size of the nano-iron powder is 140 nm; the particle size of the nano-modified 98W alloy powder is 5-25 μm, and the sphericity is 0.

95.

3. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, In step two, the volume energy density E of the first and second laser beams ranges from 525 J / mm². 3 -1000J / mm 3 The interval t ranges from 0.1s.

4. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 3, characterized in that, In step two, the laser power of the first laser beam and the second laser beam is 180W to 240W, the scanning speed is 300mm / s to 500mm / s, the laser spot diameter is 60μm, the scanning spacing is 40μm, and the powder layer thickness is 20μm; a strip scanning strategy is adopted and the layers are rotated 67° to avoid thermal stress concentration.

5. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, Step two involves obtaining the process parameters for the first and second laser beams, specifically including the following steps: Step 2.1: Using traditional LPBF technology, print the printing powder prepared in Step 1 under preset single-laser process parameters to obtain several single-laser printed samples; When printing the printing powder prepared in Step 1 using traditional LPBF technology, the preset single-laser process parameters are: laser power of 200W~450W, scanning speed of 200mm / s~600mm / s, laser spot diameter of 70μm, scanning interval of 50μm, and powder layer thickness of 30μm; Step 2.2: After grinding and polishing the single laser-printed sample, observe the internal pores and cracks of the single laser-printed sample with an optical microscope and take pictures to record them, so as to obtain the corresponding polished metallographic photos. Step 2.3: By comprehensively analyzing and comparing the polished metallographic images of each single laser-printed sample, the polished metallographic images that meet the requirements for internal pores and crack defects are selected. Step 2.4: Extract the single-laser process parameters corresponding to the polished metallographic images selected in Step 2.3; Step 2.5: Calculate the corresponding laser energy density E1 based on the single laser process parameters extracted in Step 2.

4. The laser energy density E1 calculated in steps 2.6 and 2.5 can be used as the reference value for the laser energy density E of the first laser beam and the second laser beam in step two. The laser energy density E and the laser energy density E1 satisfy the following: ΔE≤|E-E1| ΔE represents the energy offset threshold; Step 2.7: Based on the laser energy density E calculated in Step 2.6, preset the process parameters of the first laser beam and the second laser beam, and the value range of each process parameter of the first laser beam and the second laser beam satisfies the following: laser power of 180W~240W, scanning speed of 300mm / s~500mm / s, laser spot diameter of 60μm, scanning spacing of 40μm, and powder layer thickness of 20μm; thereby configuring a series of process parameter arrays for the first laser beam and the second laser beam. Step 2.8: Print the printing powder prepared in Step 1 one by one according to the process parameter array set in Step 2.7 to obtain several dual-laser printed samples. Step 2.9: After polishing the dual-laser printed sample, observe the internal pores and cracks of the dual-laser printed sample with an optical microscope and take pictures to record them, so as to obtain the corresponding polished metallographic photos. Step 2.10: By comprehensively analyzing and comparing the polished metallographic images of each dual-laser printed sample, the polished metallographic images that meet the requirements for internal pores and crack defects are selected. Step 2.11: Extract the process parameters corresponding to the polished metallographic photos selected in Step 2.

10.

6. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, In step two, both laser beams are Gaussian beams, and during the process of dual-laser additive manufacturing of the component, the heat energy distribution of the composite heat source formed by the superposition of the two laser beams in space is fitted to the following dual-laser Gaussian surface heat source function: Where: q h (x,y) represents the Gaussian surface heat source function of the two lasers, and (x,y) represents the spatial position of the composite heat source formed by the superposition of the two laser beams; η is the laser absorptivity, and P... i Let r be the power of the i-th laser beam. i Let be the radius of the i-th laser beam; The position of the i-th laser beam is calculated using the scanning speed v and the interval time t: in D is the time when the i-th laser beam starts operating. h Where L is the scan spacing and L is the length of a single scan path. χ is the floor function; i χ is a parameter used to control the direction of the i-th laser beam when the two laser beams employ a parallel scanning strategy. i =1; When two laser beams employ a zigzag scanning strategy, the parameter is...

7. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, The size deviation of the printing spot of the first and second laser beams is controlled within ±5μm.

8. The method for forming high-density, high-specific-gravity 98W alloy using dual-laser follow-printing additive manufacturing technology according to claim 1, characterized in that, The laser power deviation between the first and second laser beams is controlled within 10W.

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