Ceramic particle modified iron-based powder and additive manufacturing method thereof

Abstract

The application provides a ceramic particle modified iron-based powder and an additive manufacturing method thereof. The ceramic particle modified iron-based powder is an iron-based composite powder obtained by completely and uniformly mixing TaC particles and pure FV520B steel powder, wherein the TaC particles are completely adhered to the FV520B steel powder. The method mixes the iron-based powder and the TaC particles to be completely uniform by using a high-energy ball mill, obtains the iron-based composite powder, and performs laser powder bed melting. By using a laser powder bed melting forming system, high-performance preparation of the iron-based composite material is realized under an optimized printing process window. The application starts from the idea of ceramic particle composite strengthening and structure modification, successfully introduces uniformly distributed nanoscale TaC reinforcing particles and forms a martensite + austenite dual-phase heterogeneous structure in the sample by TaC particle doping, obtains a multi-level toughening effect like adding stones in cement and adding steel bars in concrete, and realizes the synergistic improvement of the matrix mechanical properties and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of laser additive manufacturing, and in particular to a ceramic particle-modified iron-based powder and an additive manufacturing method thereof. Background Art

[0002] FV520B steel, a martensitic precipitation-hardening stainless steel, exhibits high strength (>1000 MPa) and wear resistance, making it widely used in key components such as large blowers, compressors, impellers, and blades. However, its limited corrosion resistance severely limits its application in fields such as the chemical industry and marine engineering. Furthermore, increasing the strength of metal materials often results in a decrease in their plasticity and toughness, necessitating more precise macro- and micro-scale control and optimization methods to achieve comprehensive improvements in material properties. Particle-reinforced metal matrix composites (PMCs) can enhance the strength, hardness, wear resistance, and corrosion resistance of the metal matrix, while also enhancing material designability. While simultaneously integrating structural and functional properties, they offer a key approach to addressing the bottlenecks of traditional single metal materials, such as low strength, toughness, and poor corrosion resistance. Over the past four decades, the emergence of a wide variety of low-cost ceramic reinforcement particles and the continued maturity of various forming technologies have significantly improved the microstructure and performance stability of MMCs, garnering increasing attention for their application in critical structural components. Traditional methods for preparing metal matrix composites (MMCs), such as spark plasma sintering, hot isostatic pressing, and stir casting, face challenges such as the tendency for reinforcement particles to agglomerate and the difficulty in precisely controlling compositional uniformity. Agglomeration of reinforcement particles within the matrix is ​​a major factor in the degradation of the plastic deformation capacity of MMCs. Therefore, designing ceramic particle reinforcements with excellent synergistic reinforcement effects is crucial for the development and application of MMCs.

[0003] Laser powder bed melting is an additive manufacturing technology that is fast, flexible, material-saving, and automated. It can quickly produce metal parts with mechanical properties close to those of forgings and complex shapes, and has revolutionary significance for the development of modern manufacturing. Compared with traditional preparation methods for manufacturing metal matrix composites, laser powder bed melting has the following unique advantages: (1) During the melting and deposition of composite powders, due to the particle stacking structure mechanism, the temperature gradient and chemical concentration gradient inside the molten pool cause convection in the liquid phase in the molten pool, namely Marangoni flow. Marangoni flow promotes the uniform rearrangement of the reinforcement particles, reduces agglomeration, and ultimately forms a uniformly dispersed reinforcement structure; (2) The amount of reinforcement particles added can be flexibly adjusted according to the operating service requirements of the parts, realizing the design and manufacture of single and multi-particle reinforced metal matrix composites, breaking through the material singleness limitation of traditional processing and manufacturing technology; (3) The unique cyclic heating melting and high thermal gradient characteristics of the laser powder bed melting process are conducive to the rapid preparation and efficient control of the microstructure of metal matrix composites. In recent years, research on laser powder bed melting technology in the field of metal matrix composite manufacturing has increased significantly, especially focusing on aluminum alloys, copper alloys and nickel-based high-temperature alloys. However, there is relatively little research on additive manufacturing of ceramic particle reinforced martensitic stainless steel. Summary of the Invention

[0004] In response to the technical problems raised above, a ceramic particle-modified iron-based powder and an additive manufacturing method thereof are provided. The present invention primarily achieves synergistic improvements in the mechanical properties and corrosion resistance of the material by introducing TaC particles to form a uniformly distributed network of nanoscale TaC reinforcement particles and a martensite + austenite dual-phase heterogeneous structure.

[0005] The technical means adopted in the present invention are as follows:

[0006] A ceramic particle modified iron-based powder is an iron-based composite powder obtained by completely and evenly mixing TaC particles and pure FV520B steel powder, wherein the TaC particles are completely adhered to the FV520B steel powder.

[0007] Furthermore, the average particle size of the pure FV520B steel powder is 15 to 53 μm, and the average particle size of the TaC particles is 1 to 2 μm.

[0008] Furthermore, the content of the TaC particles is 1-4 wt%.

[0009] The present invention also provides a method for additive manufacturing of ceramic particle-modified iron-based powder, comprising the following steps:

[0010] Step 1: Obtain uniformly dispersed TaC particles, and uniformly mix the uniformly dispersed TaC particles with FV520B steel powder according to a ratio to obtain FV520B / TaC composite powder;

[0011] Step 2: Based on the FV520B / TaC composite powder, obtain the special composite powder required for laser powder bed melting, and dry the special composite powder for standby use;

[0012] Step 3: Construct a three-dimensional solid geometric model, perform layered slicing on the model, import the processed data into the laser selective melting forming equipment, and perform laser powder bed melting of the special composite powder according to the slicing data.

[0013] Furthermore, in step 1, an ultrasonic cleaner is used to perform ultrasonic vibration on the TaC particles to decompose the agglomerated particles, so as to obtain uniformly dispersed TaC particles with a purity of 99.9% and an average particle size of 1 to 2 μm.

[0014] Furthermore, in step 1, the uniformly dispersed TaC particles and FV520B steel powder are mixed in a mass ratio to form a composite powder, the composite powder is placed in a ball milling jar and ball milling balls are added according to the ratio for ball milling, and the mixture is uniformly mixed in an argon environment using a high-energy ball mill to obtain an FV520B / TaC composite powder.

[0015] Furthermore, the mass ratio of the ball milling balls to the composite powder is 1:1, wherein the ball milling balls include ball milling balls with diameters of 8 mm, 6 mm, and 3 mm, and the mass ratio of the three ball milling balls with diameters of 8 mm, 6 mm, and 3 mm is 2:1:2;

[0016] The ball milling speed of the high-energy ball mill is 200-350 rpm, and the ball milling time is 5-6 hours.

[0017] Furthermore, in step 2, the FV520B / TaC composite powder obtained in step 1 is sieved and separated from the ball milling balls to obtain a special composite powder required for laser powder bed melting;

[0018] The special composite powder is placed in a vacuum drying oven for drying at a drying temperature of 80 to 120°C and a drying time of 2 to 12 hours.

[0019] Furthermore, in step 3, the laser processing parameters, including laser power, scanning speed, line spacing, layer thickness, and exposure time, are set before processing; and a steel material with a composition similar to that of the FV520B steel powder is selected as the substrate to eliminate the effect of the dilution of the parent material composition on the chemical composition of the deposited layer.

[0020] Furthermore, in the cavity of the laser selective melting forming equipment, the oxygen content is not higher than 80 ppm, the substrate material is selected from S41500 martensitic stainless steel, and the S41500 martensitic stainless steel substrate is preheated before forming at a preheating temperature of 200°C;

[0021] The laser processing parameters are as follows: laser power of 200-500 W, scanning speed of 600-1200 mm / s, line spacing of 50-90 μm, layer thickness of 30-40 μm, and inter-layer rotation angle of 67°.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Taking into account the problem that the reinforcement phase particles are easy to agglomerate in the matrix, the present invention solves the agglomeration problem by dispersing them through ultrasonic vibration. By optimizing the ball milling process, TaC particles and FV520B steel powder are evenly mixed. The obtained composite powder is uniformly distributed, highly spherical, and has good fluidity, meeting the requirements of additive manufacturing for powder properties. The process is simple, low-cost, and suitable for large-scale production.

[0024] 2. The high-density network of TaC nanoparticles evenly distributed in the FV520B matrix can effectively accumulate dislocations and improve the dislocation storage capacity. The metastable austenite in the FV520B / TaC composite material can provide a TRIP effect during deformation, alleviate severe stress concentration, promote uniform deformation during plastic deformation, increase the strain hardening rate, and significantly improve the strength without reducing the plasticity of the material.

[0025] 3. TaC has a higher potential and can act as a cathode to form micro-galvanic corrosion with the substrate, promoting the formation of Ta2O5 passivation film and inhibiting Cl - The presence of a network structure in the FV520B / TaC composite material can also lead to a more stable bond of the passivation film, thereby increasing the difficulty of piercing the passivation film and improving the corrosion resistance of the material.

[0026] Based on the above reasons, the present invention can be widely promoted in the fields of additive manufacturing and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 Flowchart of the method of the present invention.

[0029] Figure 2 This is a powder SEM morphology of the material obtained in Comparative Example 1 of the present invention.

[0030] Figure 3 These are SEM morphologies of TaC-reinforced particles of the materials obtained in various embodiments of the present invention.

[0031] Figure 4 This is a powder SEM morphology of the material obtained in Example 3 of the present invention.

[0032] Figure 5 This is a high-magnification TEM morphology image of the material obtained in Example 3 of the present invention.

[0033] Figure 6 This is a spectrum diagram of the Ta2O5 passivation film formed on the material obtained in Example 3 of the present invention.

[0034] Figure 7 The following are X-ray diffraction patterns of the materials obtained in various embodiments and comparative examples of the present invention.

[0035] Figure 8 The stress-strain curves of the materials obtained in various embodiments and comparative examples of the present invention are shown in FIG.

[0036] Figure 9 The figures are the dynamic polarization curves of the materials obtained in various embodiments and comparative examples of the present invention.

[0037] Figure 10 2 are polarization resistance diagrams of the materials obtained in various embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] Unless otherwise specified, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments can have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0042] The present invention provides a ceramic particle-modified iron-based powder for laser additive manufacturing. The powder comprises an iron-based composite powder doped with TaC particles and pure FV520B steel powder without TaC particles. The average particle size of the pure FV520B steel powder is 15 to 53 μm. The TaC particles and FV520B steel powder are mixed by high-energy ball milling until they are completely uniform and fully adhere to each other. The TaC particles are added in an amount of 1 to 4 wt%.

[0043] TaC particles are evenly distributed and adhere to almost all of the FV520B powder. Their high nucleation ability allows them to provide a large number of non-uniform nucleation sites during the high-speed melting of the moving molten pool, increasing the nucleation rate during solidification and thus achieving significant grain refinement in the matrix. Furthermore, the high thermal conductivity of TaC particles significantly increases the solidification rate of the molten pool, enabling a solidification structure transition from planar crystals to cellular crystals in the matrix.

[0044] Compared with pure FV520B stainless steel formed by laser powder bed fusion, the ultimate tensile strength of TaC reinforced iron-based composites formed by laser powder bed fusion increased from 1071 MPa to 1550 MPa, and the polarization resistance increased from 161.8 kΩ·cm without reducing the plasticity / toughness of the material. 2 Increased to 1636.81 kΩ·cm 2 , the mechanical properties and corrosion resistance have been improved significantly.

[0045] The present invention also provides a method for additive manufacturing of ceramic particle-modified iron-based powder, which is prepared by the following steps:

[0046] (1) First, an ultrasonic cleaner was used to subject TaC particles to ultrasonic vibration for two hours to decompose the agglomerated particles, and TaC particles with a purity of 99.9% and an average particle size of 1 to 2 μm were obtained as reinforcing particles;

[0047] (2) TaC particles and FV520B steel powder were placed in a ball mill and ball milling balls were added according to the ratio. The mixture was uniformly mixed in a high-energy ball mill under argon atmosphere to obtain FV520B / TaC composite powder;

[0048] (3) Sieving and separating the composite powder obtained in step (2) from the ball milling balls to obtain a special composite powder required for laser powder bed melting, and placing the sieved special composite powder in a drying oven for drying and storage for use;

[0049] (4) Constructing a three-dimensional solid geometric model in a computer, performing layered slicing on the model, and importing the processed data into a laser selective melting forming device;

[0050] (5) Set the processing parameters such as laser power, scanning speed, line spacing, layer thickness, and exposure time during the processing; select steel (S41500 martensitic steel) with a composition similar to that of FV520B steel powder as the substrate to eliminate the effect of the dilution of the parent material composition on the chemical composition of the deposited layer;

[0051] (6) Laser powder bed melting is performed on the iron-based composite material powder obtained in step (3) according to the slicing data obtained in step (4).

[0052] In step (2), the mass ratio of the ball milling balls to the composite powder is 1:1, wherein the ball milling balls include ball milling balls with diameters of 8 mm, 6 mm, and 3 mm, and the mass ratio of the three ball milling balls with diameters of 8 mm, 6 mm, and 3 mm is 2:1:2.

[0053] The ball milling speed parameter in step (2) is set to 200-350 rpm, and the ball milling time is set to 5-6 h.

[0054] Preferably, the ball-to-material ratio of the ball milling treatment is 1:1, the ball milling speed is 350 rpm, and the ball milling time is 5 h.

[0055] In step (3), the composite powder and the ball milling balls are sieved and separated, and the composite powder is placed in a vacuum drying oven for drying at a holding temperature of 80 to 120° C. for 2 to 12 hours.

[0056] Preferably, the holding temperature during the drying process is 80° C. and the drying time is 12 hours.

[0057] In step (5), the oxygen content in the cavity of the laser selective melting forming equipment is not higher than 80 ppm. The substrate material in step (5) is S41500 martensitic stainless steel. The S41500 martensitic stainless steel substrate is preheated before forming, and the preheating temperature is 200°C.

[0058] In step (5), the laser power is 200-500 W; the scanning speed is 600-1200 mm / s; the line spacing is 50-90 μm; the layer thickness is 30-40 μm; and the interlayer rotation angle is 67°.

[0059] Preferably, the laser power is 200 W; the scanning speed is 600 mm / s; the line spacing is 70 μm; the layer thickness is 30 μm; and the inter-layer rotation angle is 67°.

[0060] Preparation Principle: During the laser powder bed fusion process of the FV520B / TaC composite, the TaC particles partially dissolve, dissolving Ta and C into the FV520B steel matrix. As austenite stabilizers, Ta and C inhibit the transformation from high-temperature austenite to martensite during solidification and cooling, resulting in an increase in retained austenite.

[0061] The formation of the network-like nanoscale TaC particle reinforcement structure in the sample is mainly attributed to the particle stacking structure mechanism during the deposition process. During the deposition process, the temperature gradient and chemical concentration gradient within the molten pool will lead to a counterclockwise Marangoni flow. When the Marangoni flow acts on the TaC reinforcement particles, the asymmetric structure of the reinforcement particles will generate torque around them. Under the combined action of the torque and the Marangoni flow, the reinforcement particles gather into a ring around the center of the Marangoni flow, promoting the uniform rearrangement of the reinforcement particles, reducing particle agglomeration, and ultimately forming a uniformly dispersed nano-TaC particle reinforcement structure.

[0062] By doping TaC particles, the nucleation rate during solidification is increased, resulting in significant refinement of the matrix grains and fine-grain strengthening. Simultaneously, the austenite content is increased to form a dual-phase heterogeneous structure of martensite + austenite. During specimen deformation, austenite yields preferentially and transforms into martensite, producing a significant double yield phenomenon and TRIP effect. This alleviates stress concentration during deformation, increases the work hardening rate, and enhances strength and toughness.

[0063] TaC nanoparticles can act as a cathode, forming micro-galvanic corrosion between the substrate and the substrate. In the initial stage of micro-galvanic corrosion, [TaCl6] - , promotes the formation of Ta2O5 passivation film and inhibits Cl - Improve the corrosion resistance of materials.

[0064] The method of the present invention uses a high-energy ball mill to mix iron-based powder and TaC particles until they are completely uniform, obtains iron-based composite powder, and performs laser powder bed melting. A laser powder bed melting forming system is used to achieve high-performance preparation of iron-based composite materials under an optimized printing process window. Starting from the idea of ​​composite strengthening and structural modification of ceramic particles, the present invention successfully introduces uniformly distributed nano-scale TaC reinforcing particles into the sample through TaC particle doping and forms a martensite + austenite dual-phase heterogeneous structure, obtaining a multi-stage strengthening and toughening effect similar to adding stones to cement and steel bars to concrete, achieving a synergistic improvement in the mechanical properties and corrosion resistance of the matrix.

[0065] In the following examples, the average particle size of pure FV520B steel powder is 15-53 μm, and the average particle size of TaC particles is 1-2 μm.

[0066] Example 1

[0067] A method for additive manufacturing of ceramic particle-modified iron-based powder, comprising the following steps:

[0068] (1) First, TaC particles were dispersed in a beaker containing anhydrous ethanol at a mass ratio of solute to solution of 1:20. Then, the mixture was placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixture was placed in a drying oven for drying at a temperature of 80 °C and a drying time of 15 h to obtain uniformly dispersed TaC particles.

[0069] (2) In a vacuum glove box protected by argon, pure FV520B steel powder and TaC particles were mixed into a composite powder in a mass ratio of 99wt%:1wt%. The mixed composite powder was placed in a ball mill and ball milling was added for ball milling. The mass ratio of ball milling balls to composite powder was 1:1. The ball milling balls included ball milling balls with diameters of 8mm, 6mm, and 3mm. The mass ratio of the three types of ball milling balls with diameters of 8mm, 6mm, and 3mm was 2:1:2. Then, an appropriate amount of alcohol was added to make the powder into a paste and distribute it on the spheres and the inner wall of the jar to improve the fluidity and viscosity of the powder, making the powder easier to disperse during the ball milling process. The ball milling speed was set to 350rpm and the ball milling time was set to 5h. After the ball milling was completed, the obtained composite powder and ball milling balls were sieved and separated to obtain an iron-based composite powder.

[0070] (3) The obtained iron-based composite powder is placed in a vacuum drying oven at 80°C for 12 hours to eliminate the influence of moisture absorption on the forming quality. The special composite powder required for laser powder bed melting is obtained.

[0071] (4) S41500 stainless steel with a similar composition to FV520B steel powder was selected as the substrate to eliminate the influence of the dilution of the parent material composition on the chemical composition of the deposited layer. Before the experiment, the substrate was cut into a size of 200 mm × 400 mm × 25 mm, and the surface of the substrate was polished clean with a grinder. Finally, it was cleaned with acetone and blown dry as a substrate material.

[0072] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with a size of 10mm×10mm×10mm and 70mm×10mm×10mm. Then use Magics software to perform layered slicing and scanning path planning on the three-dimensional solid model, and import the processed data into the laser powder bed melting equipment.

[0073] (6) Laser processing parameters include laser power, scanning speed, powder layer thickness, line spacing, and interlayer rotation angle. The laser power is 200W; the scanning speed is 600mm / s; the line spacing is 70μm; the layer thickness is 30μm; and the interlayer rotation angle is 67°.

[0074] (7) The prepared S41500 stainless steel substrate is first preheated at 200°C in a laser powder bed melting device, and then argon gas is introduced into the forming cavity. The oxygen content in the forming cavity is not higher than 80 ppm. Subsequently, the obtained iron-based composite powder is laser-molded layer by layer according to the above-mentioned slicing data to obtain the required parts.

[0075] (8) After the processing is completed, the formed block is cut from the substrate using a wire cutting process, cleaned with acetone and blown dry for later use.

[0076] In this embodiment, the TaC particles obtained after the vibration drying treatment in step (1) are as follows Figure 3 As shown by Figure 3 It can be seen that the TaC particles are uniformly dispersed and have an average particle size of 1 μm.

[0077] After grinding and polishing, the sample was identified by X-ray diffractometer. The results are as follows: Figure 7 As shown in Figure 1TaC-FV520B, the results show that only a small amount of austenite phase was detected, approximately 3.2%.

[0078] The cut standard tensile parts were subjected to three tensile tests, and the average value and standard deviation were taken. The engineering stress and strain were obtained as follows: Figure 8 As shown in 1TaC-FV520B, the tensile strength is 1229 MPa and the elongation is 9.5%.

[0079] The corrosion performance test was carried out using a sample with a cross section of 10 mm × 10 mm to evaluate the corrosion resistance of the sample; the results are shown in the figure below. Figure 9As shown in 1TaC-FV520B, the results show that the pitting potential of 1TaC-FV520B sample is 78mV.

[0080] The performance of the passivation film was evaluated by electrochemical impedance spectroscopy (EIS). Figure 10 The results show that the polarization resistance of 1TaC-FV520B sample is 324.7kΩ·cm 2 .

[0081] Example 2

[0082] A method for additive manufacturing of ceramic particle-modified iron-based powder, comprising the following steps:

[0083] (1) First, TaC particles were dispersed in a beaker containing anhydrous ethanol at a mass ratio of solute to solution of 1:20. Then, the mixture was placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixture was placed in a drying oven for drying at a temperature of 80 °C and a drying time of 15 h to obtain uniformly dispersed TaC particles.

[0084] (2) In a vacuum glove box protected by argon, pure FV520B steel powder and TaC particles were mixed into a composite powder in a mass ratio of 99wt%:2wt%. The mixed composite powder was placed in a ball mill and ball milling was added for ball milling. The mass ratio of ball milling balls to composite powder was 1:1. The ball milling balls included ball milling balls with diameters of 8mm, 6mm, and 3mm. The mass ratio of the three types of ball milling balls with diameters of 8mm, 6mm, and 3mm was 2:1:2. Then, an appropriate amount of alcohol was added to make the powder into a paste and distribute it on the spheres and the inner wall of the jar to improve the fluidity and viscosity of the powder, making the powder easier to disperse during the ball milling process. The ball milling speed was set to 350rpm and the ball milling time was set to 5h. After the ball milling was completed, the obtained composite powder and the ball milling balls were sieved and separated to obtain an iron-based composite powder.

[0085] (3) The obtained iron-based composite powder is placed in a vacuum drying oven at a drying temperature of 80°C for 12 hours to eliminate the influence of moisture absorption of the powder on the forming quality and obtain the special composite powder required for laser powder bed melting.

[0086] (4) S41500 stainless steel with a similar composition to FV520B steel powder was selected as the substrate to eliminate the influence of the dilution of the parent material composition on the chemical composition of the deposited layer. Before the experiment, the substrate was cut into a size of 200 mm × 400 mm × 25 mm, and the surface of the substrate was polished clean with a grinder. Finally, it was cleaned with acetone and blown dry as a substrate material.

[0087] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with a size of 10mm×10mm×10mm and 70mm×10mm×10mm. Then use Magics software to perform layered slicing and scanning path planning on the three-dimensional solid model, and import the processed data into the laser powder bed melting equipment.

[0088] (6) Laser processing parameters include laser power, scanning speed, powder layer thickness, line spacing, and interlayer rotation angle. The laser power is 200W; the scanning speed is 600mm / s; the line spacing is 70μm; the layer thickness is 30μm; and the interlayer rotation angle is 67°.

[0089] (7) The prepared S41500 stainless steel substrate is first preheated at 200°C in a laser powder bed melting device, and then argon gas is introduced into the forming cavity. The oxygen content in the forming cavity is not higher than 80 ppm. Subsequently, the obtained iron-based composite powder is laser-molded layer by layer according to the above-mentioned slicing data to obtain the required parts.

[0090] (8) After the processing is completed, the formed block is cut from the substrate using a wire cutting process, cleaned with acetone and blown dry for later use.

[0091] In this embodiment, the TaC particles obtained after the vibration drying treatment in step (1) are as follows Figure 3 As shown by Figure 3 It can be seen that the TaC particles are uniformly dispersed and have an average particle size of 1 μm.

[0092] After grinding and polishing, the sample was identified by X-ray diffractometer. The results are as follows: Figure 7 As shown in 2TaC-FV520B, the results show that the austenite content is 38.2%

[0093] The cut standard tensile parts were subjected to three tensile tests, and the average value and standard deviation were taken. The engineering stress and strain were obtained as follows: Figure 8 As shown in 2TaC-FV520B, the tensile strength is 1415MPa and the elongation is 10.6%.

[0094] The corrosion performance test was carried out using a sample with a cross section of 10 mm × 10 mm to evaluate the corrosion resistance of the sample; the results are shown in the figure below. Figure 9 As shown in 2TaC-FV520B, the results show that the pitting potential of 2TaC-FV520B sample is 205mV.

[0095] The performance of the passivation film was evaluated by electrochemical impedance spectroscopy (EIS). Figure 10The results show that the polarization resistance of 2TaC-FV520B sample is 863.7 kΩ·cm 2 .

[0096] Example 3

[0097] A method for additive manufacturing of ceramic particle-modified iron-based powder, comprising the following steps:

[0098] (1) First, TaC particles were dispersed in a beaker containing anhydrous ethanol at a mass ratio of solute to solution of 1:20. Then, the mixture was placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixture was placed in a drying oven for drying at a temperature of 80 °C and a drying time of 15 h to obtain uniformly dispersed TaC particles.

[0099] (2) In a vacuum glove box protected by argon, pure FV520B steel powder and TaC particles were mixed into a composite powder in a mass ratio of 99wt%:4wt%. The mixed composite powder was placed in a ball mill and ball milling was added for ball milling. The mass ratio of ball milling balls to composite powder was 1:1. The ball milling balls included ball milling balls with diameters of 8mm, 6mm, and 3mm. The mass ratio of the three types of ball milling balls with diameters of 8mm, 6mm, and 3mm was 2:1:2. Then, an appropriate amount of alcohol was added to make the powder into a paste and distribute it on the spheres and the inner wall of the jar to improve the fluidity and viscosity of the powder, making the powder easier to disperse during the ball milling process. The ball milling speed was set to 350rpm and the ball milling time was set to 5h. After the ball milling was completed, the obtained composite powder and ball milling balls were sieved and separated to obtain an iron-based composite powder.

[0100] (3) The obtained iron-based composite powder is placed in a vacuum drying oven at a drying temperature of 80°C for 12 hours to eliminate the influence of moisture absorption of the powder on the forming quality and obtain the special composite powder required for laser powder bed melting.

[0101] (4) S41500 stainless steel with a similar composition to FV520B steel powder was selected as the substrate to eliminate the influence of the dilution of the parent material composition on the chemical composition of the deposited layer. Before the experiment, the substrate was cut into a size of 200 mm × 400 mm × 25 mm, and the surface of the substrate was polished clean with a grinder. Finally, it was cleaned with acetone and blown dry as a substrate material.

[0102] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with a size of 10mm×10mm×10mm and 70mm×10mm×10mm. Then use Magics software to perform layered slicing and scanning path planning on the three-dimensional solid model, and import the processed data into the laser powder bed melting equipment.

[0103] (6) Laser processing parameters include laser power, scanning speed, powder layer thickness, line spacing, and interlayer rotation angle. The laser power is 200W; the scanning speed is 600mm / s; the line spacing is 70μm; the layer thickness is 30μm; and the interlayer rotation angle is 67°.

[0104] (7) The prepared S41500 stainless steel substrate is first preheated at 200°C in a laser powder bed melting device, and then argon gas is introduced into the forming cavity. The oxygen content in the forming cavity is not higher than 80 ppm. Subsequently, the obtained iron-based composite powder is laser-molded layer by layer according to the above-mentioned slicing data to obtain the required parts.

[0105] (8) After the processing is completed, the formed block is cut from the substrate using a wire cutting process, cleaned with acetone and blown dry for later use.

[0106] The TaC particles obtained after the vibration drying treatment in step (1) of this embodiment are as follows Figure 3 As shown by Figure 3 It can be seen that the TaC particles are uniformly dispersed and have an average particle size of 1 μm.

[0107] A TaC ceramic modified iron-based composite powder prepared by high energy ball milling Figure 4 As shown by Figure 4 It can be seen that TaC particles are evenly distributed and adhere to almost all FV520B powders.

[0108] After grinding and polishing, the sample was identified by X-ray diffractometer. The results are as follows: Figure 7 As shown in 4TaC-FV520B, the results show that the austenite content is 77.8%.

[0109] High magnification TEM image of 4TaC-FV520B sample Figure 5 As shown, it can be seen that the honeycomb structure boundary is composed of austenite and nano-TaC.

[0110] The cut standard tensile parts were subjected to three tensile tests, and the average value and standard deviation were taken. The engineering stress and strain were obtained as follows: Figure 8 As shown in 4TaC-FV520B, the tensile strength is 1550MPa and the elongation is 12.9%.

[0111] The corrosion performance test was carried out using a sample with a cross section of 10 mm × 10 mm to evaluate the corrosion resistance of the sample; the results are shown in the figure below. Figure 9 As shown in 4TaC-FV520B, the results show that the pitting potential of 4TaC-FV520B sample is 250mV.

[0112] The performance of the passivation film was evaluated by electrochemical impedance spectroscopy (EIS). Figure 10 The results show that the polarization resistance of 1TaC-FV520B sample is 1636.8 kΩ·cm 2 .

[0113] XPS test was performed on the sample after electrochemical formation of passivation film, and the results were as follows: Figure 6 As shown, it shows that a Ta2O5 passivation film is formed on the surface of the material.

[0114] Comparative Example 1

[0115] Comparative Example 1 relates to an additive manufacturing method for ceramic particle modified iron-based powder. The specific steps are basically the same as those in Example 1, except that in step (2) of Comparative Example 1, no composite powder is mixed and no ball milling is performed. Pure FV520B steel powder is directly used for laser powder bed melting. The SEM morphology of the powder morphology is as follows: Figure 2 The stress-strain curve is shown as Figure 8 As shown in FV520B, the tensile strength is 1071MPa and the elongation is 13.1%; the XRD pattern is as follows Figure 7 As shown in FV520B, the austenite content is 5.8%; the dynamic polarization curve is as follows Figure 9 As shown in Figure 2, the pitting potential of pure FV520B sample is -58mV; the electrochemical impedance spectrum is as shown in Figure 2. Figure 10 As shown, the polarization resistance of pure FV520B sample is 161.8 kΩ·cm 2 .

[0116] In summary, it can be seen from Examples 1 to 3 and Comparative Example 1 that Example 3 has the best performance. Example 3 significantly improves the strength and corrosion resistance without reducing the plasticity / toughness of the material. This is mainly attributed to the doping of TaC particles, which increases the nucleation rate during solidification, thereby achieving significant refinement of the matrix grains, and inhibits the transformation of the material from high-temperature austenite to martensite structure during solidification and cooling to form an austenite + martensite dual-phase heterogeneous structure. Due to the Marangoni flow in the molten pool, the strengthening particles under the action of the Marangoni flow eventually form a nano-scale TaC reinforcement structure with a uniform network distribution. The network structure boundary is composed of an austenite phase network and TaC nanoparticles. The austenite phase is soft and the TaC particles are hard, which improves the strength of the material. At the same time, the sample shows obvious double yield phenomenon and TRIP effect during tensile deformation, thereby alleviating stress concentration and significantly improving the work hardening rate, and improving the strength and toughness of the material. TaC has a higher electrochemical potential, can act as a cathode and form micro-galvanic corrosion with the matrix, promote the formation of Ta2O5 passivation film and inhibit Cl -The presence of a network structure in the FV520B / TaC composite material can also lead to a more stable bond of the passivation film, thereby increasing the difficulty of piercing the passivation film and improving the corrosion resistance of the material.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for additive manufacturing of ceramic particle-modified iron-based powder, characterized in that: The ceramic particle modified iron-based powder is an iron-based composite powder obtained by completely and evenly mixing TaC particles and pure FV520B steel powder, wherein the TaC particles are completely adhered to the pure FV520B steel powder; The average particle size of the pure FV520B steel powder is 15-53 μm, and the average particle size of the TaC particles is 1-2 μm; The content of the TaC particles is 1-4 wt %; The additive manufacturing method of the ceramic particle-modified iron-based powder comprises the following steps: Step 1: Obtain uniformly dispersed TaC particles, and uniformly mix the uniformly dispersed TaC particles with pure FV520B steel powder according to a ratio to obtain FV520B / TaC composite powder; In the step 1, an ultrasonic cleaner is used to perform ultrasonic vibration on the TaC particles to decompose the agglomerated particles to obtain uniformly dispersed TaC particles with a purity of 99.9% and an average particle size of 1 to 2 μm; In the step 1, uniformly dispersed TaC particles and pure FV520B steel powder are mixed in a mass ratio to form a composite powder, the composite powder is placed in a ball milling jar and ball milling balls are added according to the ratio for ball milling, and the mixture is uniformly mixed in an argon environment using a high-energy ball mill to obtain an FV520B / TaC composite powder; The mass ratio of the ball milling balls to the composite powder is 1:1, wherein the ball milling balls include ball milling balls with diameters of 8 mm, 6 mm, and 3 mm, and the mass ratio of the three ball milling balls with diameters of 8 mm, 6 mm, and 3 mm is 2:1:2; The ball milling speed of the high-energy ball mill is 200-350 rpm, and the ball milling time is 5-6 h; Step 2: Based on the FV520B / TaC composite powder, obtain the ceramic particle-modified iron-based powder required for laser powder bed melting, and dry the ceramic particle-modified iron-based powder for later use; In step 2, the FV520B / TaC composite powder obtained in step 1 is sieved and separated from the ball milling balls, and the sieved composite powder is placed in a vacuum drying oven for drying at a temperature of 80 to 120° C. for a drying time of 2 to 12 hours to obtain the ceramic particle-modified iron-based powder required for laser powder bed melting; Step 3: construct a three-dimensional solid geometric model, perform layered slicing on the model, import the processed data into a laser selective melting forming device, and perform laser powder bed melting of the ceramic particle modified iron-based powder according to the slicing data; In the cavity of the laser selective melting forming equipment, the oxygen content is not higher than 80ppm. The substrate material is S41500 martensitic stainless steel. The S41500 martensitic stainless steel substrate is preheated before forming at a preheating temperature of 200°C. The laser powder bed fusion forming parameters are: laser power of 200~500W, scanning speed of 600~1200mm / s, line spacing of 50~90μm, layer thickness of 30~40μm, and interlayer rotation angle of 67°.

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