Method for realizing crack closing of tungsten component prepared by SLM (selective laser melting) based on SPS (spark plasma sintering)

Abstract

The invention belongs to the technical field of metal additive manufacturing post-processing, and relates to a method for achieving crack closing of a tungsten component prepared through SLM based on SPS. The method mainly comprises the following steps that S1, a tungsten component is prepared, specifically, a pure tungsten component is prepared through a selective laser melting (SLM) technology; s2, the SLM forming component is subjected to surface cleaning and support removing treatment, and after it is ensured that no powder residues exist, accurate positioning and placing treatment is conducted; and S3, SPS treatment process: putting the graphite mold treated in the step S2 into SPS equipment for sintering treatment. Through the combined action of high temperature and mechanical pressure, inevitable microcracks in the SLM pure tungsten component are effectively closed, and the compactness and integrity of the component are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of post-processing of metal additive manufacturing, and relates to a method for achieving crack closure of a tungsten component prepared by SLM based on SPS. Background Art

[0002] Tungsten is the metal with the highest melting point in current industrial applications. It has the characteristics of high density, high hardness, good thermal conductivity, strong corrosion resistance, high elastic modulus, high thermal shock resistance, and low expansion coefficient. It is widely used in military, chemical, medical, aerospace, aviation, nuclear industry, electronics and other fields.

[0003] Tungsten and its alloys are typically formed using processes such as extrusion and forging. However, due to their high ductile-brittle transition temperature, they are brittle at room temperature and are prone to cracking and breaking during processing. Powder sintering can be used to produce tungsten and its alloy plates and bars in a variety of specifications and sizes. However, conventional sintered tungsten products have disadvantages such as low density, low strength, poor plasticity, and difficult-to-control impurity content, which greatly limits their application. In addition, the powder metallurgy method makes it easy for pores to remain and impurities to be mixed in the material, further increasing the brittleness of the tungsten material. At the same time, in actual applications, the structure of tungsten parts is often complex, usually with features such as curved surfaces, curved pipes, holes and grooves, and thin walls, making it difficult to manufacture complex parts using traditional methods.

[0004] Selective Laser Melting (SLM) technology, as a typical representative of metal additive manufacturing, has a high degree of structural design freedom, excellent material utilization, and mold-free personalized manufacturing capabilities due to its layer-by-layer melting and construction method. In addition, SLM can also achieve organizational control at the micro level by regulating laser energy density, scanning strategy, and path mode, and has the potential for macro-micro integrated optimization of components. However, due to the inherent brittleness, low thermal conductivity, poor laser absorption, and large solidification shrinkage of tungsten materials, typical defects such as microcracks, pores, lack of fusion, and segregation are very likely to occur during the rapid solidification process of the SLM molten pool, seriously affecting the density, reliability, and service performance of the components.

[0005] To improve the overall performance of pure tungsten components produced by SLM, researchers typically use methods such as process parameter optimization, alloying design, hot isostatic pressing (HIP), or vacuum annealing to control defects and enhance mechanical properties. However, these methods generally suffer from long processing cycles and high equipment costs. Furthermore, these methods are still unable to prevent or repair the inevitable cracks that occur during the SLM forming of tungsten components. Therefore, how to effectively suppress or repair microcracks has become a key breakthrough direction in current tungsten-based additive manufacturing research. Summary of the Invention

[0006] To achieve these objectives, the present invention provides a method for crack closure in tungsten components fabricated by SLM (Small Layer Metal Leasing) based on spark plasma sintering (SPS). By combining transient heating with applied loads, this method effectively closes microcracks and increases the density of pure tungsten components produced by SLM. This method maintains the overall size and structure of the component, offers an efficient and controllable process, and is suitable for the post-processing of high-precision, high-end components.

[0007] The technical solution adopted by the present invention is a method for achieving crack closure of tungsten components prepared by SLM based on SPS, which mainly includes the following steps:

[0008] Step S1: Preparation of tungsten components: Selective laser melting (SLM) process is used to prepare pure tungsten components;

[0009] Step S2: Clean the surface of the SLM-molded component and remove the support to ensure that there is no powder residue, and then perform precise positioning and placement;

[0010] Step S3: SPS treatment process: the graphite mold treated in step S2 is placed in an SPS device for sintering.

[0011] Furthermore, the step S2 specifically includes:

[0012] S2.1: Place the cube component with its XOY face vertically and its XOZ face horizontally;

[0013] S2.2: Place the arranged components in a cylindrical graphite mold and fill the mold cavity with 5-10g of alumina powder;

[0014] S2.3: Preload pressure to 25 MPa.

[0015] Furthermore, the step S3 specifically includes:

[0016] S3.1: Evacuate the chamber of the SPS equipment;

[0017] S3.2: Add argon gas to a vacuum of 1.0-2.0×103 to prevent oxidation of components;

[0018] S3.3: Under argon protection, the system temperature is rapidly raised to 1100-1400°C at a rate of 100°C / min, and the axial pressure is increased from the preload value of 25 MPa to 30-40 MPa.

[0019] S3.4: Depending on the size of the component, hold the component at 1100-1400°C and 30-40 MPa for 15-60 minutes to promote crack closure.

[0020] S3.5: Take out the SPS furnace after it has cooled naturally to room temperature of 25-30°C to avoid secondary cracks caused by thermal shock.

[0021] Furthermore, the S3.4 is specifically: when the component volume is less than 200mm 3 When treating, a lower temperature of 1100-1200℃, a pressure of 30-35MPa and a holding time of 15-30 minutes are used;

[0022] When the component volume is greater than 200mm 3 , increase the temperature to 1200-1400℃, the pressure to 35-40MPa, and extend the holding time to 30-60 minutes.

[0023] The beneficial effects of the present invention are:

[0024] (1) Through the combined action of high temperature and mechanical pressure, the inevitable microcracks in SLM pure tungsten components are effectively closed, significantly improving the density and integrity of the components.

[0025] (2) The technical solution of the present invention has a short process, strong adaptability, is non-toxic and pollution-free, and has low cost. It is suitable for tungsten and tungsten-based components and other high-melting-point, brittle material (such as pure tungsten) components; it meets the requirements of industrial-scale application.

[0026] (3) The technical solution of the present invention fills the current process gap and can achieve the closure of microcracks in SLM pure tungsten components. 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 only 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 work.

[0028] Figure 1 This is a schematic diagram of a pure tungsten component formed by SLM;

[0029] Figure 2 This is a schematic diagram of SPS processing of pure tungsten components;

[0030] Figure 3 Figures 2 and 3 are internal morphologies of pure tungsten components before and after SPS treatment; (a) is without SPS treatment, (b) is treated by the method of Example 1, (c) is treated by the method of Example 2, (d) is treated by the method of Comparative Example 1, and (e) is treated by the method of Comparative Example 2.

[0031] The numbers shown in the figure are: 1-scanning galvanometer, 2-laser beam, 3-molded part, 4-crack, 5-pressing head, 6-graphite mold, 7-alumina powder, 8-graphite punch, 9-Ar gas protection, 10-pressure. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] A method for achieving crack closure of a tungsten component by SLM based on SPS mainly comprises the following steps:

[0034] 1. Tungsten component preparation: Pure tungsten components are produced using the Selective Laser Melting (SLM) process. These components have a complex microstructure and a high density (98%), but inevitably contain defects such as microcracks.

[0035] 2. For SLM formed components, such as Figure 1 As shown, necessary surface cleaning and support removal are performed to ensure that there is no powder residue, and then precise positioning is performed, specifically:

[0036] (1) Place the printed cube component with its XOY surface vertical and its XOZ surface horizontal;

[0037] (2) Place the component placed in step (1) in a cylindrical graphite mold and fill the mold cavity with 5-10g of alumina powder; the alumina powder must fully wrap the component in all directions to ensure uniform heat conduction and limit the movement of the component during the pressurization process;

[0038] (3) The preload pressure is increased to 25 MPa to form a preliminary stable powder component composite system.

[0039] 3. SPS processing, such as Figure 2 As shown, the graphite mold containing the component is placed in the SPS equipment and sintered according to the following process:

[0040] (1) Vacuuming: First, vacuumize the furnace cavity;

[0041] (2) Introduce inert gas: Then slowly introduce argon gas until the vacuum degree is (1.0-2.0)×10 3 To prevent oxidation of components;

[0042] (3) Heating and pressurizing: Under argon protection, the system is rapidly heated to 1100-1400°C at a heating rate of 100°C / min, while gradually increasing the axial pressure from the preload value of 25 MPa to 30-40 MPa;

[0043] (4) Insulation stage: Depending on the size of the component, maintain the temperature at 1100-1400℃ and 30-40MPa for 15-60 minutes to promote crack closure;

[0044] Among them, when the component volume is less than 200mm 3 When treating, a lower temperature of 1100–1200°C, a pressure of 30–35 MPa, and a short time of 15–30 minutes are used;

[0045] When the component volume is greater than 200mm 3 , increase the temperature to 1200-1400℃, the pressure to 35-40MPa, and extend the holding time to 30-60 minutes.

[0046] (5) Cooling stage: Cool naturally to room temperature of 25-30℃ in the SPS furnace and take it out to avoid secondary cracks caused by thermal shock.

[0047] The following is further described with reference to the embodiments.

[0048] Example 1:

[0049] 1. Tungsten component preparation: Pure tungsten components are produced using the Selective Laser Melting (SLM) process. These components have a complex microstructure and a high density (98%), but inevitably contain defects such as microcracks.

[0050] 2. Perform necessary surface cleaning and support removal on the SLM-molded components to ensure there is no powder residue, and then perform precise positioning and placement. Specifically:

[0051] (1) Place the printed cube component with its XOY surface vertical and its XOZ surface horizontal;

[0052] (2) placing the component placed in step (1) in a cylindrical graphite mold and filling the mold cavity with 5 g of alumina powder; the alumina powder fully wraps the component in all directions to ensure uniform heat conduction and limit the movement of the component during the pressurization process;

[0053] (3) The preload pressure is increased to 25 MPa to form a preliminary stable powder component composite system.

[0054] 3. SPS treatment process. Place the graphite mold with components into the SPS equipment and sinter according to the following process:

[0055] (1) Vacuuming: First, vacuumize the furnace cavity;

[0056] (2) Introduce inert gas: Then slowly introduce argon gas until the vacuum degree reaches 1.0×10 3 To prevent oxidation of components;

[0057] (3) Heating and pressurizing: Under argon protection, the system was rapidly heated to 1100°C at a heating rate of 100°C / min, while the axial pressure was gradually increased from the preload value of 25 MPa to 30 MPa;

[0058] (4) Holding stage: Maintaining the temperature at 1100°C and 30 MPa for 15 minutes to promote crack closure;

[0059] (6) Cooling stage: Cool naturally to room temperature of 25℃ in the SPS furnace and take it out to avoid secondary cracks caused by thermal shock.

[0060] The internal morphology of the pure tungsten component treated according to the above method is as follows Figure 3 (b) shown.

[0061] Example 2:

[0062] 1. Tungsten component preparation: Pure tungsten components are produced using the Selective Laser Melting (SLM) process. These components have a complex microstructure and a high density (98%), but inevitably contain defects such as microcracks.

[0063] 2. Perform necessary surface cleaning and support removal on the SLM-molded components to ensure there is no powder residue, and then perform precise positioning and placement. Specifically:

[0064] (1) Place the printed cube component with its XOY surface vertical and its XOZ surface horizontal;

[0065] (2) placing the component placed in step (1) in a cylindrical graphite mold and filling the mold cavity with 10 g of alumina powder; the alumina powder fully wraps the component in all directions to ensure uniform heat conduction and limit the movement of the component during the pressurization process;

[0066] (3) The preload pressure is increased to 25 MPa to form a preliminary stable powder component composite system.

[0067] 3. SPS treatment process. Place the graphite mold with components into the SPS equipment and sinter according to the following process:

[0068] (1) Vacuuming: First, vacuumize the furnace cavity;

[0069] (2) Introduce inert gas: Then slowly introduce argon gas until the vacuum degree reaches 2.0×10 3 To prevent oxidation of components;

[0070] (3) Heating and pressurizing: Under argon protection, the system is rapidly heated to 1400°C at a heating rate of 100°C / min, while the axial pressure is gradually increased from the preload value of 25 MPa to 40 MPa;

[0071] (4) Holding stage: Maintaining the temperature at 1200°C and 40 MPa for 15 minutes to promote crack closure;

[0072] (7) Cooling stage: Cool naturally to room temperature of 25℃ in the SPS furnace and take it out to avoid secondary cracks caused by thermal shock.

[0073] The internal morphology of the pure tungsten component treated according to the above method is as follows Figure 3 (c) shown.

[0074] Comparative Example 1:

[0075] The difference from Example 1 is (4) the heat preservation stage: maintaining the temperature at a set temperature of 1000° C. and 40 MPa for 5 minutes.

[0076] The internal morphology of the pure tungsten component treated according to the above method is as follows Figure 3 (d) shown.

[0077] Comparative Example 2:

[0078] The difference from Example 2 is that (4) the heat preservation stage is maintained at a set temperature of 1500°C and 25 MPa for 15 minutes.

[0079] The internal morphology of the pure tungsten component treated according to the above method is as follows Figure 3 (e) shown.

[0080] In summary, by adopting the technical solution of the present invention, the microcracks of SLM pure tungsten components can be closed through the combined action of high temperature and mechanical pressure, significantly improving the density and integrity of the components.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for achieving crack closure of tungsten components by SLM based on SPS, characterized in that: The main steps include: Step S1: Preparation of tungsten components: Selective laser melting (SLM) process is used to prepare pure tungsten components; Step S2: Clean the surface of the SLM-molded component and remove the support to ensure that there is no powder residue, and then perform precise positioning and placement; Step S3: SPS treatment process: the graphite mold treated in step S2 is placed in an SPS device for sintering.

2. The method for achieving crack closure of a tungsten component by SLM based on SPS according to claim 1, characterized in that: The step S2 specifically includes: S2.1: Place the cube component with its XOY face vertically and its XOZ face horizontally; S2.2: Place the arranged components in a cylindrical graphite mold and fill the mold cavity with 5-10g of alumina powder; S2.3: Preload pressure to 25 MPa.

3. The method for achieving crack closure of a tungsten component by SLM based on SPS according to claim 1, characterized in that: The step S3 specifically comprises: S3.1: Evacuate the chamber of the SPS equipment; S3.2: Add argon gas until the vacuum degree is 1.0-2.0×10 3 To prevent oxidation of components; S3.3: Under argon protection, the system temperature is rapidly raised to 1100-1400°C at a rate of 100°C / min, and the axial pressure is increased from the preload value of 25 MPa to 30-40 MPa. S3.4: Depending on the size of the component, hold the component at 1100-1400°C and 30-40 MPa for 15-60 minutes to promote crack closure. S3.5: Take out the SPS furnace after it has cooled naturally to room temperature of 25-30°C to avoid secondary cracks caused by thermal shock.

4. The method for achieving crack closure of a tungsten component by SLM based on SPS according to claim 3, characterized in that: S3.4 specifically states: When the component volume is less than 200mm 3 When treating, a lower temperature of 1100-1200℃, a pressure of 30-35MPa and a holding time of 15-30 minutes are used; When the component volume is greater than 200mm 3 , increase the temperature to 1200-1400℃, the pressure to 35-40MPa, and extend the holding time to 30-60 minutes.

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