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

Abstract

The invention provides ceramic particle modified iron-based powder and an additive manufacturing method thereof. The ceramic particle modified iron-based powder is iron-based composite powder obtained by completely and uniformly mixing TaC particles and pure FV520B steel powder, wherein the TaC particles and the FV520B steel powder are completely adhered. According to the method, iron-based powder and TaC particles are mixed to be completely uniform through a high-energy ball mill, and iron-based composite powder is obtained and subjected to laser powder bed melting. A laser powder bed melting forming system is adopted, and under an optimized printing process window, high-performance preparation of the iron-based composite material is achieved. Starting from the idea of ceramic particle composite reinforcement and structure modification, through TaC particle doping, nanoscale TaC reinforced particles which are uniformly distributed in a net shape are successfully introduced into a sample, a martensite and austenite dual-phase heterostructure is formed, and a multi-stage strengthening and toughening effect like that stones are added into cement and reinforcing steel bars are added into concrete is obtained; the synergistic improvement of the mechanical property and the corrosion resistance of the matrix is realized.

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] As a martensitic precipitation hardening stainless steel, FV520B steel has high strength (>1000MPa) and wear resistance, and is widely used in key components such as large blowers, compressors, impellers, and blades. However, due to its general corrosion resistance, its application in the chemical industry and marine engineering is severely limited. At the same time, the improvement of metal material strength often leads to a decrease in plasticity / toughness, and more precise macro / micro cross-scale regulation and optimization methods are needed to achieve a comprehensive improvement in material performance. Particle-reinforced metal matrix composites can improve the strength, hardness, wear resistance, corrosion resistance and other properties of the metal matrix and the designability of the material, while also having the characteristics of structural and functional integration. It is an important way to solve the bottleneck problems of low strength and toughness and poor corrosion resistance of traditional single metal materials. In the past four decades, due to the emergence of a wide variety of low-cost ceramic reinforced particles and the continuous maturity of various forming technologies, the stability of the organization and performance of metal matrix composites has been greatly improved, and its application in key structural parts has received more and more attention. Traditional methods for preparing metal matrix composites, such as spark plasma sintering, hot isostatic pressing and stir casting, are faced with the challenges of easy agglomeration of reinforcement particles and difficulty in precisely controlling the uniformity of composition. Agglomeration of reinforcement particles in the matrix is ​​an important reason for the degradation of the plastic deformation capacity of metal matrix composites. Therefore, designing ceramic particle reinforcements with excellent synergistic reinforcement effects is crucial to the development and application of metal matrix composites.

[0003] Laser powder bed melting technology is an additive manufacturing technology with the characteristics of rapidity, flexibility, material saving, and automation. It can quickly manufacture metal parts with mechanical properties close to forgings and complex shapes, which has revolutionary significance for the development of modern manufacturing. Compared with traditional preparation methods for manufacturing metal matrix composites, laser powder bed melting technology has the following unique advantages: (1) During the melting and deposition process of composite powder, 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 finally forms a uniformly dispersed reinforcement structure; (2) The amount of reinforcement particles added can be flexibly adjusted according to the service requirements of the parts, realizing the design and manufacturing 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 regulation 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, while research on additive manufacturing of ceramic particle reinforced martensitic stainless steel is relatively less. Summary of the invention

[0004] According to the technical problems raised above, a ceramic particle modified iron-based powder and an additive manufacturing method thereof are provided. The present invention mainly introduces TaC particles to form uniformly distributed nano-scale TaC reinforced particles and a martensite + austenite dual-phase heterogeneous structure, thereby achieving a synergistic improvement in the mechanical properties and corrosion resistance of the material.

[0005] The technical means adopted by 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 15-53 μm, and the average particle size of the TaC particles is 1-2 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, obtaining uniformly dispersed TaC particles, and uniformly mixing 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 a laser selective melting forming device, and perform laser powder bed melting forming on the special composite powder according to the slicing data.

[0013] Furthermore, in the 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 the step 1, the uniformly dispersed TaC particles and FV520B steel powder are mixed into a composite powder according to a mass ratio, the composite powder is placed in a ball milling jar and ball milling balls are added according to the ratio for ball milling treatment, and the mixture is uniformly mixed in an argon environment by a high-energy ball mill to obtain a FV520B / TaC composite powder.

[0015] Further, 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 temperature of 80 to 120°C and a drying time of 2 to 12 hours.

[0019] Furthermore, in step 3, 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 influence 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 80ppm, the substrate material is selected to be S41500 martensitic stainless steel, and the S41500 martensitic stainless steel substrate is preheated before forming, and the preheating temperature is 200°C;

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

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

[0023] 1. The present invention takes into account the problem that the reinforcement phase particles are easy to agglomerate in the matrix, and solves the agglomeration problem by dispersing them through ultrasonic vibration. The TaC particles and FV520B steel powder are evenly mixed by optimizing the ball milling process. The obtained composite powder has uniform distribution, high sphericity and good fluidity, which meets 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 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 TRIP effect during deformation, alleviate severe stress concentration, promote uniform deformation during plastic deformation, increase strain hardening rate, and significantly improve strength without reducing material plasticity.

[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 the network structure in the FV520B / TaC composite material can also lead to a more stable combination 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0028] Figure 1 Flow chart of the method of the present invention.

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

[0030] Figure 3 The SEM morphology images of TaC reinforced particles of the materials obtained in various embodiments of the present invention are shown.

[0031] Figure 4 This is a powder SEM morphology image 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 from 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] Fig. 9 The figures are the dynamic polarization curves of the materials obtained in the embodiments and comparative examples of the present invention.

[0037] Fig.10 Graphs showing polarization resistance of materials obtained from various embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments 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 by no means 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 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, 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 the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method 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 exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain 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, which is an iron-based powder for laser additive manufacturing, comprising an iron-based composite powder doped with TaC particles and a pure FV520B steel powder without TaC particles, wherein the average particle size of the pure FV520B steel powder is 15 to 53 μm. The TaC particles and the FV520B steel powder are mixed by high-energy ball milling until they are completely uniform and completely adhere to the TaC particles and the FV520B steel powder, wherein the addition amount of the TaC particles is 1 to 4 wt%.

[0043] TaC particles are evenly distributed and adhere to almost all FV520B powders. TaC particles have high nucleation ability and can provide a large number of non-uniform nucleation sites during the high-speed melting process of the moving molten pool, increasing the nucleation rate during solidification, thereby achieving significant refinement of the matrix grains. At the same time, the high thermal conductivity of TaC particles can significantly increase the solidification rate of the molten pool and realize the solidification structure transformation of the matrix from planar crystals to cellular crystals.

[0044] Compared with pure FV520B stainless steel formed by laser powder bed melting, the ultimate tensile strength of TaC reinforced iron-based composites formed by laser powder bed melting increased from 1071MPa to 1550MPa, and the polarization resistance increased from 161.8kΩ·cm to 161.8kΩ·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) firstly, an ultrasonic cleaner is used to perform ultrasonic vibration on TaC particles for two hours to decompose the agglomerated particles, and obtain TaC particles with a purity of 99.9% and an average particle size of 1 to 2 μm as reinforcement particles;

[0047] (2) putting TaC particles and FV520B steel powder into a ball mill and adding ball milling balls according to the ratio, and uniformly mixing them in a high-energy ball mill under argon environment protection to obtain FV520B / TaC composite powder;

[0048] (3) sieving and separating the composite powder obtained in step (2) and 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 later 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) Setting processing parameters such as laser power, scanning speed, line spacing, layer thickness, and exposure time during processing; using steel (S41500 martensitic steel) with a composition similar to that of FV520B steel powder as the substrate to eliminate the effect of parent material composition dilution on the chemical composition of the deposited layer;

[0051] (6) Performing laser powder bed melting 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 types of 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 hours.

[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 temperature of 80 to 120° C. for a treatment time of 2 to 12 hours.

[0056] Preferably, the insulation 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 melting process of FV520B / TaC composite materials, TaC particles partially dissolve, and Ta and C elements dissolve in the FV520B steel matrix. As austenite stabilizing elements, Ta and C elements inhibit the transformation of the material from high-temperature austenite to martensite during solidification and cooling, resulting in an increase in the content of 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 inside 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, which promotes the uniform rearrangement of the reinforcement particles, reduces particle agglomeration, and finally forms a uniformly dispersed nano TaC particle reinforcement structure.

[0062] By doping TaC particles, the nucleation rate during solidification is increased, thereby achieving significant refinement of matrix grains and fine grain strengthening. At the same time, the austenite content increases to form a dual-phase heterogeneous structure of martensite + austenite. During the deformation of the sample, austenite yields first and transforms into martensite, resulting in obvious double yield phenomenon and TRIP effect, alleviating stress concentration during deformation, increasing work hardening rate, and improving strength and toughness.

[0063] TaC nanoparticles can act as a cathode to form microgalvanic corrosion with the substrate. In the initial stage of microgalvanic corrosion, [TaCl6] - , promoting the formation of Ta2O5 passivation film and inhibiting Cl - Intrusion, 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 networked 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 like 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, and then placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixed solution 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%, and the mixed composite powder was placed in a ball milling jar, and ball milling balls were added for ball milling, wherein the mass ratio of ball milling balls to composite powder was 1:1, wherein the ball milling balls included ball milling balls with diameters of 8mm, 6mm, and 3mm, and the mass ratio of 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 distributed on the sphere and the inner wall of the jar, to improve the fluidity and viscosity of the powder, so that the powder was 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.

[0070] (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. The special composite powder required for laser powder bed melting is obtained.

[0071] (4) S41500 stainless steel with a similar composition to that of FV520B steel powder was selected as the substrate to eliminate the effect 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 dried as a substrate material.

[0072] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with dimensions of 10 mm × 10 mm × 10 mm and 70 mm × 10 mm × 10 mm. 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 200 W; the scanning speed is 600 mm / s; the line spacing is 70 μm; the layer thickness is 30 μm; 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-formed 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 the average particle size is 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 1TaC-FV520B, the results show that only a small amount of austenite phase was detected, about 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 1229MPa 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 Fig. 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). Fig.10 The results show that the polarization resistance of the 1TaC-FV520B sample is 324.7 kΩ·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, and then placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixed solution 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 are mixed into a composite powder in a mass ratio of 99wt%:2wt%, and the mixed composite powder is placed in a ball milling jar, and ball milling balls are added for ball milling treatment, wherein the mass ratio of ball milling balls to composite powder is 1:1, wherein the ball milling balls include ball milling balls with diameters of 8mm, 6mm, and 3mm, and the mass ratio of three types of ball milling balls with diameters of 8mm, 6mm, and 3mm is 2:1:2; then an appropriate amount of alcohol is added to make the powder into a paste and distribute it on the sphere and the inner wall of the jar, thereby improving the fluidity and viscosity of the powder and making the powder easier to disperse during the ball milling process. The ball milling speed is set to 350rpm, and the ball milling time is set to 5h. After the ball milling is completed, the obtained composite powder is sieved and separated from the ball milling balls 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 a drying time of 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 that of FV520B steel powder was selected as the substrate to eliminate the effect 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 dried as a substrate material.

[0087] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with dimensions of 10 mm × 10 mm × 10 mm and 70 mm × 10 mm × 10 mm. 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 200 W; the scanning speed is 600 mm / s; the line spacing is 70 μm; the layer thickness is 30 μm; 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-formed 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 the average particle size is 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 Fig. 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). Fig.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, and then placed in an ultrasonic cleaner with a power of 200 W for ultrasonic vibration for 2 h. After the vibration, the mixed solution 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%, and the mixed composite powder was placed in a ball milling jar, and ball milling balls were added for ball milling, wherein the mass ratio of ball milling balls to composite powder was 1:1, wherein the ball milling balls included ball milling balls with diameters of 8mm, 6mm, and 3mm, and the mass ratio of 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 paste-like and distributed on the sphere and the inner wall of the jar, to improve the fluidity and viscosity of the powder, so that the powder was 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.

[0100] (3) The obtained iron-based composite powder is placed in a vacuum drying oven at a drying temperature of 80°C for a drying time of 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 that of FV520B steel powder was selected as the substrate to eliminate the effect 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 dried as a substrate material.

[0102] (5) Use Soildworks modeling software to build a three-dimensional solid geometric model with dimensions of 10 mm × 10 mm × 10 mm and 70 mm × 10 mm × 10 mm. 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 200 W; the scanning speed is 600 mm / s; the line spacing is 70 μm; the layer thickness is 30 μm; 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-formed 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 the average particle size is 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 Fig. 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). Fig.10 The results show that the polarization resistance of the 1TaC-FV520B sample is 1636.8 kΩ·cm 2 .

[0113] XPS test was performed on the sample after electrochemical formation of passivation film. The results are as follows Figure 6 As shown, it indicates 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, and its specific steps are basically the same as those of Example 1, except that in step (2) of Comparative Example 1, no composite powder is mixed and no ball milling is performed, and 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 in Figure 8 As shown in FV520B, the tensile strength is 1071MPa and the elongation is 13.1%; the XRD image is as follows Figure 7 As shown in FV520B, the austenite content is 5.8%; the dynamic polarization curve is as follows Fig. 9 As shown in Figure 2, the pitting potential of pure FV520B sample is -58mV; the electrochemical impedance spectrum is shown in Figure 2 Fig.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 Marangoni flow eventually form a nanoscale 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 exhibits 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 the network structure in the FV520B / TaC composite material can also lead to a more stable combination 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 ceramic particle modified iron-based powder, characterized in that: The iron-based composite powder is 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.

2. The ceramic particle-modified iron-based powder according to claim 1, characterized in that: 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.

3. The ceramic particle-modified iron-based powder according to claim 1, characterized in that: The content of the TaC particles is 1-4 wt %.

4. A method for additive manufacturing of ceramic particle-modified iron-based powder according to any one of claims 1 to 3, characterized in that: The steps include: Step 1, obtaining uniformly dispersed TaC particles, and uniformly mixing the uniformly dispersed TaC particles with FV520B steel powder according to a ratio to obtain FV520B / TaC composite powder; 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; 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 forming on the special composite powder according to the slicing data.

5. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 4, characterized in that: In the 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.

6. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 4, characterized in that: In the step 1, the uniformly dispersed TaC particles and FV520B steel powder are mixed into a composite powder according to a mass ratio, the composite powder is put into a ball milling jar, and ball milling balls are added according to the ratio for ball milling treatment, and the mixture is uniformly mixed in an argon environment by a high-energy ball mill to obtain a FV520B / TaC composite powder.

7. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 6, characterized in that: 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 hours.

8. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 6, characterized in that: In the step 2, the FV520B / TaC composite powder obtained in the step 1 is sieved and separated from the ball milling balls to obtain a special composite powder required for laser powder bed melting; The special composite powder is placed in a vacuum drying oven for drying at a temperature of 80 to 120°C and a drying time of 2 to 12 hours.

9. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 4, characterized in that: In step 3, laser processing parameters are set before processing, including laser power, scanning speed, line spacing, layer thickness, and exposure time; and a steel material with a composition similar to that of 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.

10. The additive manufacturing method of ceramic particle-modified iron-based powder according to claim 9, characterized in that: 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 processing parameters are as follows: laser power is 200-500 W, scanning speed is 600-1200 mm / s, line spacing is 50-90 μm, layer thickness is 30-40 μm, and interlayer rotation angle is 67°.

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