Ultra-fine grain high-strength and high-toughness ODS steel components and photocuring additive manufacturing method

Abstract

The present invention relates to the technical field of metal additive manufacturing, and provides an ultrafine-grained high-strength and high-toughness ODS steel component and a photocuring additive manufacturing method. The method includes precursor preparation, photocuring additive manufacturing, and heat treatment. Based on the additive manufacturing method, the present invention can customize the structure according to the working conditions to obtain complex ODS steel components with arbitrary shapes, which can fully meet the service requirements under harsh working conditions such as nuclear energy systems; the photocuring printing process adopted has low equipment cost, wide raw material sources and is easy to obtain, and has the potential for mass production; it will not introduce defects such as thermal cracking in the ODS steel, and has a relatively high density; it can obtain a grain structure with nanoscale size, can ensure the number of grain boundaries, and the prepared ODS steel has high strength and good toughness; combined with an appropriate sintering process, nano-precipitates precipitate in the grains, and the high-temperature performance is more stable.

Description

Technical Field

[0001] The present invention relates to the technical field of metal additive manufacturing, and particularly to an ultrafine-grained high-strength and high-toughness ODS steel component and a photocuring additive manufacturing method. Background Art

[0002] ODS steel refers to oxide dispersion strengthened steel. Due to having high-temperature stable nano-oxide phases and grain boundaries, it has extremely excellent high-temperature mechanical properties and anti-irradiation properties, and can serve in a nuclear energy system with extremely harsh environments. It is considered an ideal material for key components in future nuclear energy systems.

[0003] Traditionally, a saturated solid solution powder is usually prepared by mechanical alloying, and an ODS steel component is obtained after pressing and heat treatment. For example, CN114737103A discloses a method for efficiently preparing ODS steel by mechanical alloying and its product. An alloy powder is obtained by mixing and ball milling a pre-alloyed powder and a metal oxide powder, and an ODS steel is sintered and formed by combining spark plasma technology; or an ODS steel billet is obtained by a casting process. For example, CN115029612A discloses an ODS steel and its preparation method, and an ODS steel is obtained by melting, reduction, refining and casting.

[0004] However, with the miniaturization and high efficiency of nuclear energy systems, the demand for ODS steel components with complex shapes and customized specific 3D structures in some special service occasions has become increasingly prominent, and traditional preparation methods are difficult to meet. The rise of additive manufacturing technology provides a new way for the preparation of complex-shaped ODS steel components. For example, CN106868383B discloses a method for preparing a nanostructured ODS steel workpiece by 3D printing technology. Using selective laser melting technology, a complex OSD steel part with nano-precipitation phases is prepared by adding a substrate containing Zr element.

[0005] However, for laser additive manufacturing based on high-energy beam laser melting (including selective laser melting technology and direct energy deposition technology), due to the rapid melting and solidification process, the prepared components usually face inevitable problems such as cracking, stress concentration and element segregation. In addition, in order to ensure the fluidity of the powder, laser additive manufacturing requires micro-powder as the raw material, which is difficult to ensure the grain size and the number of grain boundaries of the ODS steel matrix, and has a more serious impact on the high-temperature service performance and anti-irradiation performance of ODS steel.

[0006] In summary, there is currently a lack of an additive manufacturing method that can prepare ODS steel with complex shapes and good properties. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an ultrafine-grained high-strength and high-toughness ODS steel component and a photocuring additive manufacturing method, which can stably, quickly and low-cost obtain non-segregated high-strength and high-toughness ODS steel complex components composed of nano-grains.

[0008] The present invention adopts the following technical solution:

[0009] In one aspect, the present invention provides a method for photo-curing additive manufacturing of an ultrafine-grained, high-strength, high-toughness ODS steel component, comprising:

[0010] S1. Precursor preparation: a certain proportion of oxidant, fuel, iron source and dispersion source are dissolved in deionized water, and the solution is volatilized, concentrated and decomposed under stirring conditions to obtain oxide precursor powder after reaction;

[0011] S2. Photocuring additive manufacturing: fully mixing a certain proportion of the oxide precursor powder and a photosensitive material to prepare a photosensitive slurry, and performing additive manufacturing using a photocuring printer to obtain a precursor blank;

[0012] S3. Heat treatment: placing the precursor blank in a heat treatment furnace, and performing degreasing, reduction and sintering at a certain temperature and atmosphere to obtain an ultrafine-grained, high-strength and high-toughness ODS steel component.

[0013] Any possible implementation as described above further provides an implementation, in which in step S1, the oxidant is ammonium nitrate.

[0014] Any possible implementation as described above, further provides an implementation, in step S1, the iron source is a water-soluble iron salt, and the water-soluble iron salt is one of ferric sulfate, ferric chloride, and ferric nitrate; the fuel is one or more of oxidants such as glucose, urea, citric acid, and glycine; the diffusion source is one or more of yttrium nitrate, lanthanum nitrate, and aluminum sulfate.

[0015] Any possible implementation as described above further provides an implementation, in step S1, the molar ratio of the iron source is 40-60%, the molar ratio of the fuel is 10-50%, the molar ratio of the oxidant is 5-30%, and the molar ratio of the dispersion source is 1-5%.

[0016] Any possible implementation as described above further provides an implementation, in which in step S2, the volume ratio of the oxide precursor in the photosensitive slurry is 40-60%.

[0017] For any of the possible implementation manners described above, a further implementation manner is provided. In step S2, the photosensitive material includes acrylic photosensitive resin monomers, acrylic photosensitive resin prepolymers, photoinitiators, and additives; the mixing manner of the oxide precursor powder and the photosensitive resin is vacuum high-energy ball milling.

[0018] Photosensitive resins are some unsaturated acrylic monomers containing carbon-carbon double bonds.

[0019] Photoinitiators can activate these photosensitive resin molecules. When irradiated with ultraviolet light of a specific wavelength, the carbon-carbon double bonds open and link with each other, linking monomer molecules into long-chain molecules, that is, a cross-linking reaction occurs. Macroscopically, the liquid resin turns into solid plastic. The photoinitiators include one or more of ethyl 2,4,6-trimethylbenzoyl phenylphosphinate (TPO-L), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (TPO), and 1-hydroxycyclohexyl phenyl ketone (184), and their mass ratio to the photosensitive resin is 1%-5%;

[0020] There are two types of additives. One is surface-modified and adheres to the surface of the powder, enabling the powder to be evenly dispersed in the organic matter, reducing the viscosity of the system, and facilitating printing. The other is light-absorbing. Since ultraviolet light will undergo diffuse reflection when irradiated on the powder, resulting in a mismatch between the actual cured pattern and the designed model, the light absorber can absorb the scattered light to ensure printing accuracy. The additives include one or more of hydroquinone, tert-butylhydroquinone, tert-butylcatechol, UNIQSPERSE 9450, UNIQJET 9510, Modaflow2100, EFKA PX 4701, AgiSyn 008, RJ10, and P115, and their mass ratio to the photosensitive resin is 5-10%.

[0021] For any of the possible implementation manners described above, a further implementation manner is provided. In step S2, the photocuring printer includes photocuring printers such as digital light processing (DLP) printers and stereolithography apparatus (SLA) printers.

[0022] For any of the possible implementation manners described above, a further implementation manner is provided. In step S3, the heat treatment furnace is a tube furnace or a muffle furnace; the degreasing atmosphere is an inert atmosphere or air, and the degreasing temperature is 500-700°C; the reduction atmosphere is hydrogen, and the reduction temperature is 500-600°C; the sintering atmosphere is hydrogen, and the sintering temperature is 850-1000°C.

[0023] For any of the possible implementation manners described above, a further implementation manner is provided. The inert atmosphere includes argon and nitrogen.

[0024] On the other hand, the present invention also provides an ultrafine-grained high-strength and high-toughness ODS steel component, which is prepared by the above method.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. Based on the additive manufacturing method, the structure can be customized according to the working conditions, and complex ODS steel components with arbitrary shapes can be obtained, which can fully meet the service requirements under harsh working conditions such as nuclear energy systems.

[0027] 2. The stereolithography printing process adopted has low equipment cost, wide raw material sources and is easy to obtain, and has the potential for mass production.

[0028] 3. The stereolithography printing process adopted will not introduce defects such as thermal cracking in the ODS steel, and has a high density.

[0029] 4. By reducing the nano-oxide precursor, a nano-sized grain structure can be obtained, which can ensure the number of grain boundaries. The prepared ODS steel has high strength and good toughness; combined with an appropriate sintering process, nano-precipitates precipitate in the grains, and the high-temperature performance is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure shows a flowchart of a stereolithography additive manufacturing method for an ultrafine-grained high-strength and high-toughness ODS steel component according to an embodiment of the present invention.

[0031] Figure 2 The figure shows the microstructure diagram of the ODS steel prepared in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The specific embodiments of the present invention will be described in detail below with reference to the specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered as isolated, and they can be combined with each other to achieve better technical effects.

[0033] As Figure 1 shown, a stereolithography additive manufacturing method for an ultrafine-grained high-strength and high-toughness ODS steel component according to an embodiment of the present invention includes:

[0034] S1. Preparation of the precursor: Dissolve a certain proportion of oxidant, fuel, iron source and dispersion source in deionized water, and under stirring conditions, let the solution volatilize, concentrate and decompose, and obtain the oxide precursor powder after the reaction;

[0035] S2. Stereolithography additive manufacturing: Fully mix a certain proportion of the oxide precursor powder and photosensitive material to obtain a photosensitive slurry, and use a stereolithography printer for additive manufacturing to obtain a precursor green body;

[0036] S3. Heat treatment: Place the precursor green body in a heat treatment furnace and perform debinding, reduction, and sintering under certain temperature and atmosphere conditions to obtain an ultrafine-grained, high-strength, and high-toughness ODS steel component.

[0037] In a specific embodiment, the oxidizing agent is ammonium nitrate.

[0038] In a specific embodiment, in step S1, the iron source is a water-soluble iron salt, which is one of ferric sulfate, ferric chloride, and ferric nitrate; the fuel is one or more of oxidizing agents such as glucose, urea, citric acid, and glycine; the dispersion source is one or more of yttrium nitrate, lanthanum nitrate, and aluminum sulfate.

[0039] In a specific embodiment, in step S1, the molar ratio of the iron source is 40 - 60%, the molar ratio of the fuel is 10 - 50%, the molar ratio of the oxidizing agent is 5 - 30%, and the molar ratio of the dispersion source is 1 - 5%.

[0040] In a specific embodiment, in step S2, the volume ratio of the oxide precursor in the photosensitive slurry is 40 - 60%.

[0041] In a specific embodiment, in step S2, the photosensitive material includes an acrylic photosensitive resin monomer, an acrylic photosensitive resin prepolymer, a photoinitiator, and an additive; the mixing method of the oxide precursor powder and the photosensitive resin is vacuum high-energy ball milling.

[0042] In a specific embodiment, in step S2, the photocuring printer includes photocuring printers such as a digital light processing (DLP) printer and a stereolithography apparatus (SLA) printer.

[0043] In a specific embodiment, in step S3, the heat treatment furnace is a tube furnace or a muffle furnace; the debinding atmosphere is an inert atmosphere or air, and the debinding temperature is 500 - 700 °C; the reduction atmosphere is hydrogen, and the reduction temperature is 500 - 600 °C; the sintering atmosphere is hydrogen, and the sintering temperature is 850 - 1000 °C.

[0044] In a specific embodiment, the inert atmosphere includes argon and nitrogen.

[0045] Example 1

[0046] A photocuring additive manufacturing method for an ultrafine-grained, high-strength, and high-toughness ODS steel component, comprising:

[0047] S1. Weigh 0.1 mol of ferric nitrate, 0.3 mol of glycine, 0.3 mol of ammonium nitrate, and 0.01 mol of yttrium nitrate, dissolve them in deionized water, place them on an electric furnace, stir and heat simultaneously. After a series of reactions such as volatilization, concentration, and decomposition, obtain a precursor powder.

[0048] S2. Mix 50 parts of precursor powder and 50 parts of photosensitive material by volume, then ball-mill them in a vacuum ball mill for 20 hours to obtain a photosensitive slurry. Place the slurry in a DLP printer to start printing and obtain a precursor green body.

[0049] S3. Place the precursor green body in a heat treatment furnace. In an argon atmosphere, heat it to 700 °C at a heating rate of 1 °C / min and hold for 2 hours. After cooling, then in an air atmosphere, heat it to 600 °C at a heating rate of 5 °C / min and hold for 2 hours; after cooling, in a hydrogen atmosphere, heat it to 600 °C at a heating rate of 10 °C / min and hold for 2 hours, then heat it to 980 °C at a heating rate of 5 °C / min and hold for 1.5 hours, and cool it with the furnace to obtain an ODS steel component.

[0050] From Figure 2 It can be seen that the grains of the prepared ODS steel are all nanoscale, and there are dispersion-precipitated strengthening phases inside the grains, which can effectively improve the strength and toughness of the ODS steel.

[0051] Example 2

[0052] A method for photocuring additive manufacturing of an ultrafine-grained high-strength and high-toughness ODS steel component, comprising:

[0053] S1. Weigh 0.1 mol of ferric sulfate, 0.3 mol of glucose, 0.5 mol of ammonium nitrate, and 0.01 mol of lanthanum nitrate. Dissolve them in deionized water and place them on an electric furnace to heat with stirring. After a series of reactions such as volatilization, concentration, and decomposition, obtain precursor powder.

[0054] S2. Mix 50 parts of precursor powder and 50 parts of photosensitive material by volume, then ball-mill them in a vacuum ball mill for 20 hours to obtain a photosensitive slurry. Place the slurry in an SLA printer to start printing and obtain a precursor green body.

[0055] S3. Place the precursor green body in a heat treatment furnace. In an argon atmosphere, heat it to 700 °C at a heating rate of 1 °C / min and hold for 2 hours. After cooling, then in an air atmosphere, heat it to 600 °C at a heating rate of 5 °C / min and hold for 2 hours; after cooling, in a hydrogen atmosphere, heat it to 600 °C at a heating rate of 10 °C / min and hold for 2 hours, then heat it to 980 °C at a heating rate of 5 °C / min and hold for 1.5 hours, and cool it with the furnace to obtain an ODS steel component.

[0056] Example 3

[0057] A method for photocuring additive manufacturing of an ultrafine-grained high-strength and high-toughness ODS steel component, comprising:

[0058] S1. Weigh 0.1 mol of ferric chloride, 0.4 mol of glycine, 0.3 mol of ammonium nitrate, and 0.01 mol of yttrium nitrate. After dissolving them in deionized water, place the solution on an electric furnace and heat it while stirring. After a series of reactions such as volatilization, concentration, and decomposition, a precursor powder is obtained.

[0059] S2. Mix 50 parts of the precursor powder and 50 parts of the photosensitive material according to the volume ratio, and then ball-mill them in a vacuum ball mill for 20 hours to obtain a photosensitive slurry. Place the slurry in a DLP printer to start printing and obtain a precursor green body.

[0060] S3. Place the precursor green body in a heat treatment furnace. In an argon atmosphere, heat it at a heating rate of 1 °C / min to 700 °C, hold for 2 hours, and then cool it. Then, in an air atmosphere, heat it at a heating rate of 5 °C / min to 600 °C, hold for 2 hours; after cooling, in a hydrogen atmosphere, heat it at a heating rate of 10 °C / min to 600 °C, hold for 2 hours, heat it at a heating rate of 5 °C / min to 980 °C, hold for 1.5 hours, and then cool it with the furnace to obtain an ODS steel component.

[0061] The innovation points of the present invention are described as follows:

[0062] 1. In the existing metal 3D printing technology, since laser scanning is performed after powder spreading for each layer, the powder needs to have a certain fluidity. However, the fluidity of nano-powder is very poor, so the powder used in the existing technology is all micro-powder (nano-powder cannot be used). The grain size of the metal parts prepared using micro-powder is relatively large, at the micron level. In contrast, the present invention uses nano-oxide powder, and the metal grains of the ODS steel components prepared by the process of the present invention are at the nano-level, which is much smaller than the grain size of the metals prepared by traditional 3D printing technology. Therefore, the copper parts prepared in this application have better quality.

[0063] 2. Using the process of the present invention, the grain size of the ODS steel is controlled within 200 nm, and the minimum can reach 50 nm. Through the uniformly dispersed yttrium oxide (or lanthanum oxide, alumina) strengthening phase and a large number of grain boundaries in the crystal, the compressive strength and true strain can reach 2.12 GPa - 8% and 1.52 GPa - 54%, which are much better than those of the ODS steel prepared by traditional processes.

[0064] 3. The heat treatment process of the present invention is unique and is divided into three steps: degumming, reduction, and sintering. According to traditional concepts, when reducing a solid part or blank using a reducing agent such as hydrogen (without damaging the part or blank), only the surface of the part or blank can be reduced, and the interior of the part or blank cannot be reduced, so a pure metal part cannot be obtained. Through a large number of practices, the inventor found that the heat treatment process of the present invention can perfectly solve this technical problem, which is described as follows: The nano-powders are dispersed in glue (i.e., photosensitive resin). After the photosensitive resin is exposed, it changes from a liquid to a solid and forms a blank together with the nano-powders. During the degreasing process, the resin gradually cracks and volatilizes, and all the resin will be removed as the temperature rises. At this time, the powders are loosely combined with each other by friction, and the blank is very porous (has voids). When the blank is heated in a hydrogen atmosphere, hydrogen can fully penetrate into the interior of the blank through the pores, and a reduction reaction occurs to reduce the oxide to pure steel. During sintering, the temperature is further increased, and the contacting steel powders start to change from physical contact to chemical contact and are tightly combined together. At this time, the blank will shrink in size. By continuing to keep it warm, the loose blank is sintered into a dense pure ODS steel block part. The experimental results show that the prepared part is a pure ODS steel part and does not contain unreduced iron oxide.

[0065] 5. Using nano-oxides as precursors, no gas is released during the degreasing stage, and no gas is generated during the self-heating process of the powders, which can completely avoid the introduction of cracks and pores.

[0066] The present invention uses chemically synthesized nano-oxides as precursors. After printing and heat treatment, ODS steel special-shaped parts with extremely fine grains can be obtained.

[0067] Although several embodiments of the present invention have been given in this article, those skilled in the art should understand that the embodiments in this article can be changed without departing from the spirit of the present invention. The above embodiments are only exemplary and should not be used as the limitation of the scope of the rights of the present invention.

Claims

1. A method for photocuring additive manufacturing of an ultrafine-grained high-strength and high-toughness ODS steel component, characterized in that, The method includes: S1. Preparation of precursor: Dissolve a certain proportion of oxidant, fuel, iron source, and dispersion source in deionized water. Under stirring conditions, let the solution volatilize, concentrate, and decompose. After the reaction, obtain oxide precursor powder. The dispersion source is one or more of yttrium nitrate, lanthanum nitrate, and aluminum sulfate. S2. Photocuring additive manufacturing: Thoroughly mix a certain proportion of the oxide precursor powder and photosensitive material to obtain a photosensitive slurry. Use a photocuring printer for additive manufacturing to obtain a precursor green body. S3. Heat treatment: Place the precursor green body in a heat treatment furnace. Under certain temperature and atmosphere, perform degreasing, reduction, and sintering to obtain an ultrafine-grained high-strength and high-toughness ODS steel component.

2. The photocuring additive manufacturing method for the ultrafine-grained high-strength and high-toughness ODS steel component according to claim 1, characterized in that, In step S1, the oxidant is ammonium nitrate.

3. The photocuring additive manufacturing method of the ultrafine-grained high-strength and high-toughness ODS steel member according to claim 1, characterized in that, In step S1, the iron source is a water-soluble iron salt, and the water-soluble iron salt is one of ferric sulfate, ferric chloride, and ferric nitrate. The fuel is one or more of glucose, urea, citric acid, and glycine.

4. The photocuring additive manufacturing method for the ultrafine-grained high-strength and high-toughness ODS steel member according to claim 1 or 3, characterized in that, In step S1, the molar ratio of the iron source is 40 - 60%, the molar ratio of the fuel is 10 - 50%, the molar ratio of the oxidant is 5 - 30%, and the molar ratio of the dispersion source is 1 - 5%.

5. The photocuring additive manufacturing method for the ultrafine-grained high-strength and high-toughness ODS steel component according to claim 1, characterized in that, In step S2, the volume ratio of the oxide precursor in the photosensitive slurry is 40 - 60%.

6. The photocuring additive manufacturing method for the ultrafine-grained high-strength and high-toughness ODS steel component according to claim 1, characterized in that, In step S2, the photosensitive material includes acrylic photosensitive resin monomer, acrylic photosensitive resin prepolymer, photoinitiator, and additive. The mixing method of the oxide precursor powder and the photosensitive material is vacuum high-energy ball milling. The additive includes one or more of hydroquinone, tert-butylhydroquinone, tert-butylcatechol, UNIQSPERSE 9450, UNIQJET 9510, Modaflow2100, EFKA PX 4701, AgiSyn 008, RJ10, and P115, and its mass ratio to the photosensitive resin is 5 - 10%.

7. The photocuring additive manufacturing method of the ultrafine-grained high-strength and high-toughness ODS steel member according to claim 1, characterized in that, In step S2, the photocuring printer is a digital surface exposure printer or a stereolithography printer.

8. The photocuring additive manufacturing method of the ultrafine-grained high-strength and high-toughness ODS steel component according to claim 1, characterized in that, In step S3, the heat treatment furnace is a tube furnace or a muffle furnace. The degreasing atmosphere is an inert atmosphere or air, and the degreasing temperature is 500 - 700°C. The reduction atmosphere is hydrogen, and the reduction temperature is 500 - 600°C. The sintering atmosphere is hydrogen, and the sintering temperature is 850 - 1000°C.

9. The photocuring additive manufacturing method of the ultrafine-grained high-strength and high-toughness ODS steel member according to claim 8, characterized in that, The inert atmosphere is argon and nitrogen.

10. An ultrafine-grained high-strength and high-toughness ODS steel component, characterized in that, The ultrafine-grained high-strength and high-toughness ODS steel component is obtained by the method according to any one of claims 1 - 9.

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