A binder for binder jet additive manufacturing, method of making and method of use

Abstract

The present application provides a kind of binder for binder jetting additive manufacturing, preparation method and use method. Polyvinylpyrrolidone is used as base material for consolidating metal powder, ethylene glycol is used as humectant to improve the wettability of the binder on the surface of metal powder, ethylene glycol monobutyl ether is used as leveling agent to reduce the surface tension of the binder, 2-pyrrolidone is used as stabilizer to maintain the chemical uniformity and stability of the binder, deionized water is used as solvent, by using different average molecular weight polyvinylpyrrolidone mixture as base material, both the flow permeability of the binder and the strength of the green body obtained by printing are ensured. Further, soluble salt copper acetate and metal organic framework material MOFs are added to the binder, MOFs are used to adsorb free copper ions to dissolve more copper acetate in the binder, copper acetate is decomposed into nanoparticles at high temperature, which effectively improves the density of the final sintered part, and avoids the problem of nozzle blockage.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing, and more specifically to an adhesive for adhesive spraying additive manufacturing, its preparation method, and its application method. Background Technology

[0002] Binder jet printing (BJ), as a method of additive manufacturing, binds metal or ceramic powders by jetting binder layer by layer to form a preform. Compared with selective laser melting (SLM) and direct energy deposition (DED), it has advantages such as safety and stability, high speed, low cost, and uniform part structure, which is conducive to the mass production of metal, ceramic, and composite parts.

[0003] Binders play a crucial role in BJ additive manufacturing, affecting the forming accuracy and component residue of products, and thus determining the performance of the final parts. The core components of existing binders are mostly classified, and developing environmentally friendly and high-performance binders requires extensive experimentation. Therefore, mastering independently controllable new binder formulations and R&D technologies is of paramount importance.

[0004] One of the challenges facing BJ technology is improving green strength. Current solutions involve using polymers with larger molecular weights and higher post-consolidation strength as binder bases, but this suffers from poor flowability and penetration. A second challenge is increasing density. Current solutions use binders containing nanoparticles to enhance density, but this leads to nozzle clogging and uneven spraying issues during production. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a binder for binder spraying additive manufacturing with good fluidity, which effectively improves the surface morphology and density of the product, as well as its preparation method and application method.

[0006] Technical solution: A binder for binder spray additive manufacturing, the binder comprising the following components in parts by weight: 10-15 parts base material, 5-10 parts ethylene glycol, 5-10 parts ethylene glycol monobutyl ether, 5-10 parts 2-pyrrolidone, and 60-70 parts deionized water.

[0007] Optionally, the base material is polyvinylpyrrolidone with an average molecular weight of 40,000.

[0008] Optionally, the base material is obtained by uniformly mixing polyvinylpyrrolidone with different average molecular weights, with an average molecular weight range of 10,000 to 100,000.

[0009] Preferably, the base material is obtained by mixing polyvinylpyrrolidone with average molecular weights of 24,000, 40,000 and 58,000 in a mass ratio of 1:1:1.

[0010] Preferably, the adhesive further includes 1-5 parts of anhydrous copper acetate and 0.01-5 parts of metal-organic framework (MOF) materials.

[0011] Specifically, the metal-organic framework materials (MOFs) include Cu-MOF and Al-MOF.

[0012] The present invention also provides a method for preparing an adhesive for adhesive spraying additive manufacturing, comprising the following steps:

[0013] (1) Add ethylene glycol to deionized water at room temperature and stir for 5 minutes;

[0014] (2) Add ethylene glycol monobutyl ether to the system obtained in step (1) and stir for 5 minutes;

[0015] (3) Add 2-pyrrolidone to the system obtained in step (2) and stir for 5 minutes;

[0016] (4) Add polyvinylpyrrolidone to the system obtained in step (3) and stir for 30 minutes to obtain the adhesive.

[0017] Preferably, metal-organic framework materials (MOFs) are added to the system obtained in step (4) above, and stirred for 30 minutes. Then anhydrous copper acetate is added and stirred for 30 minutes to obtain the binder.

[0018] The present invention also provides a method for using an adhesive in adhesive spraying additive manufacturing, comprising the following steps:

[0019] (1) Printing blank: The binder and metal powder are placed into the printing device to print a blank of the set shape;

[0020] (2) Drying solvent: Place the blank obtained in step (1) in an oven, set the temperature to 180℃, and keep it at that temperature for 4 to 8 hours;

[0021] (3) Debonding of the billet: The billet obtained in step (2) is placed in a tube furnace and heated to 600°C at a heating rate of 2°C / min under an H2 atmosphere with a flow rate of 300 ml / min, and held for 7 h.

[0022] (4) Sintering of the blank: The blank obtained in step (3) is placed in a tube furnace with the H2 flow rate unchanged. The temperature is increased to 850°C at a rate of 5°C / min and held for 1.5h. Then the temperature is increased to 1380°C at a rate of 5°C / min and held for 4h. The blank is then cooled to room temperature to obtain the sintered part.

[0023] Specifically, the metal powder includes 316L stainless steel powder, SKH-9 mold steel powder, and M2 tool steel powder.

[0024] Beneficial effects: Compared with the prior art, the significant effects of this invention are as follows: This invention uses polyvinylpyrrolidone as a base material to solidify metal powder, ethylene glycol as a humectant to improve the wetting performance of the binder on the surface of the metal powder, ethylene glycol monobutyl ether as a leveling agent to reduce the surface tension of the binder, 2-pyrrolidone as a stabilizer to maintain the chemical homogeneity and stability of the binder, and deionized water as a solvent. By using a mixture of polyvinylpyrrolidone with different average molecular weights as the base material, both the flow and permeability of the binder are ensured, and the strength of the green body obtained by printing is improved. Furthermore, soluble salt anhydrous copper acetate and metal-organic framework materials (MOFs) are added to the binder. MOFs are used to adsorb free copper ions to dissolve more copper acetate in the binder. At high temperature, copper acetate decomposes into nanoparticle copper, which effectively improves the density of the final sintered part and avoids the problem of nozzle clogging. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the microstructure of the interaction between the binder of this invention and 316L stainless steel powder.

[0026] Figure 2 These are schematic diagrams of the blanks obtained in Embodiments 1 to 3 of the present invention.

[0027] Figure 3 These are schematic diagrams of the 316L stainless steel sintered parts obtained in Examples 1 to 3 of the present invention.

[0028] Figure 4 This is a metallographic image of the SKH-9 mold steel sintered part in Embodiment 4 of the present invention.

[0029] Figure 5 This is a metallographic image of the M2 tool steel sintered part in Embodiment 4 of the present invention. Detailed Implementation

[0030] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0031] In this embodiment, the printing parameters are: powder layer thickness 60μm, powder spreading speed 10mm / s, and binder saturation 90%.

[0032] Example 1:

[0033] An adhesive for adhesive spraying additive manufacturing, the adhesive comprising the following components in parts by weight: 12 parts polyvinylpyrrolidone, 7 parts ethylene glycol, 7 parts ethylene glycol monobutyl ether, 7 parts 2-pyrrolidone, and 67 parts deionized water.

[0034] In this embodiment, the average molecular weight of polyvinylpyrrolidone is 40,000.

[0035] Preparation method:

[0036] Step 1: At room temperature, add ethylene glycol to deionized water and stir for 5 minutes;

[0037] Step 2: Add ethylene glycol monobutyl ether to the system obtained in Step 1 and stir for 5 minutes;

[0038] Step 3: Add 2-pyrrolidone to the system obtained in Step 2 and stir for 5 minutes;

[0039] Step 4: Add polyvinylpyrrolidone to the system obtained in Step 3, stir for 30 minutes, and obtain the binder.

[0040] How to use:

[0041] In this embodiment, 316 stainless steel powder is used, and the powder particle size is controlled within the range of 0 to 15 μm. During the printing process, some solvents of the binder will evaporate, causing the base material to solidify and bind the metal powder, thus achieving the effect of preform shape preservation.

[0042] Step 1: Printing the blank: Place the adhesive and 316 stainless steel powder into the printing device and print the blank;

[0043] Step 2: Drying the solvent: Place the blank obtained in step (1) in an oven, set the temperature to 180℃, and keep it at that temperature for 4 to 8 hours;

[0044] Step 3: Debonding of the billet: Place the billet obtained in step (2) in a tube furnace, heat it to 600℃ at a heating rate of 2℃ / min in an H2 atmosphere with a flow rate of 300ml / min, and hold it for 7h.

[0045] Step 4: Sintering of the billet: Place the billet obtained in step (3) in a tube furnace, keep the H2 flow rate constant, heat it to 850°C at a heating rate of 5°C / min, hold it for 1.5h, then heat it to 1380°C at a heating rate of 5°C / min, hold it for 4h, and cool it to room temperature to obtain 316L stainless steel sintered parts.

[0046] Example 2:

[0047] An adhesive for adhesive spraying additive manufacturing, the adhesive comprising the following components in parts by weight: 12 parts polyvinylpyrrolidone, 7 parts ethylene glycol, 7 parts ethylene glycol monobutyl ether, 7 parts 2-pyrrolidone, and 67 parts deionized water.

[0048] In this embodiment, the 12 parts of polyvinylpyrrolidone were obtained by uniformly mixing 4 parts of polyvinylpyrrolidone with an average molecular weight of 24,000, 4 parts with an average molecular weight of 40,000, and 4 parts with an average molecular weight of 58,000.

[0049] Preparation method:

[0050] Step 1: At room temperature, add ethylene glycol to deionized water and stir for 5 minutes;

[0051] Step 2: Add ethylene glycol monobutyl ether to the system obtained in Step 1 and stir for 5 minutes;

[0052] Step 3: Add 2-pyrrolidone to the system obtained in Step 2 and stir for 5 minutes;

[0053] Step 4: Add polyvinylpyrrolidone to the system obtained in Step 3, stir for 30 minutes, and obtain the binder.

[0054] How to use:

[0055] In this embodiment, 316 stainless steel powder is used, and the powder particle size is controlled within the range of 0 to 15 μm.

[0056] Step 1: Printing the blank: Place the adhesive and 316 stainless steel powder into the printing device and print the blank;

[0057] Step 2: Drying the solvent: Place the blank obtained in step (1) in an oven, set the temperature to 180℃, and keep it at that temperature for 4 to 8 hours;

[0058] Step 3: Debonding of the billet: Place the billet obtained in step (2) in a tube furnace, heat it to 600℃ at a heating rate of 2℃ / min in an H2 atmosphere with a flow rate of 300ml / min, and hold it for 7h.

[0059] Step 4: Sintering of the billet: Place the billet obtained in step (3) in a tube furnace, keep the H2 flow rate constant, heat it to 850°C at a heating rate of 5°C / min, hold it for 1.5h, then heat it to 1380°C at a heating rate of 5°C / min, hold it for 4h, and cool it to room temperature to obtain 316L stainless steel sintered parts.

[0060] Example 3:

[0061] An adhesive for adhesive spraying additive manufacturing, the adhesive comprising the following components in parts by weight: 12 parts polyvinylpyrrolidone, 7 parts ethylene glycol, 7 parts ethylene glycol monobutyl ether, 7 parts 2-pyrrolidone, 2 parts Cu-MOF, 3 parts anhydrous copper acetate, and 67 parts deionized water.

[0062] In this embodiment, the 12 parts of polyvinylpyrrolidone were obtained by uniformly mixing 4 parts of polyvinylpyrrolidone with an average molecular weight of 24,000, 4 parts with an average molecular weight of 40,000, and 4 parts with an average molecular weight of 58,000.

[0063] Preparation method:

[0064] Step 1: At room temperature, add ethylene glycol to deionized water and stir for 5 minutes;

[0065] Step 2: Add ethylene glycol monobutyl ether to the system obtained in Step 1 and stir for 5 minutes;

[0066] Step 3: Add 2-pyrrolidone to the system obtained in Step 2 and stir for 5 minutes;

[0067] Step 4: Add polyvinylpyrrolidone to the system obtained in Step 3, stir for 30 minutes, and obtain the binder.

[0068] Step 5: Add the metal-organic framework material Cu-MOF to the system obtained in Step 4, stir for 30 minutes, then add anhydrous copper acetate and stir for 30 minutes.

[0069] How to use:

[0070] In this embodiment, 316 stainless steel powder is used, and the powder particle size is controlled within the range of 0 to 15 μm.

[0071] Step 1: Printing the blank: Place the adhesive and 316 stainless steel powder into the printing device and print the blank;

[0072] Step 2: Drying the solvent: Place the blank obtained in step (1) in an oven, set the temperature to 180℃, and keep it at that temperature for 4 to 8 hours;

[0073] Step 3: Debonding of the billet: Place the billet obtained in step (2) in a tube furnace, heat it to 600℃ at a heating rate of 2℃ / min in an H2 atmosphere with a flow rate of 300ml / min, and hold it for 7h.

[0074] Step 4: Sintering of the billet: Place the billet obtained in step (3) in a tube furnace, keep the H2 flow rate constant, heat it to 850°C at a heating rate of 5°C / min, hold it for 1.5h, then heat it to 1380°C at a heating rate of 5°C / min, hold it for 4h, and cool it to room temperature to obtain 316L stainless steel sintered parts.

[0075] The adhesives prepared in Examples 1 to 3 are all liquid at room temperature, with a surface tension of 20 to 40 mN / m and a viscosity of 10 to 20 mPa·s, all of which meet the requirements for normal and stable ejection of adhesive from the printer nozzle.

[0076] Please refer to Figure 1 As shown, the 316L stainless steel powder mixed with the binder has a uniformly distributed microstructure.

[0077] Please refer to Figure 2As shown, from top to bottom, the blanks obtained from Examples 1 to 3 are the printed blanks. The blank obtained from Example 1 did not deform, crack, or shed a large amount of powder during the handling process; the blank obtained from Example 2, under the same printing parameters, showed reduced surface layering texture and improved surface quality; the blank obtained from Example 3, under the same printing parameters, had a smooth surface with a slight bluish tint, and improved precision and mechanical strength.

[0078] Please refer to Figure 3 As shown, the 316L stainless steel sintered parts obtained in Examples 1 to 3 all have smooth surfaces with a metallic luster. The density of the 316L stainless steel sintered parts obtained in Examples 1 to 3, measured by Archimedes' displacement method, reached 97.0%, 97.8%, and 98.3%, respectively.

[0079] Example 4:

[0080] To verify the applicability of the binder of the present invention to other types and particle sizes of metal powders, SKH-9 mold steel powder with a particle size distribution of 0 to 15 μm and M2 tool steel powder with a particle size distribution of 15 to 53 μm were used to replace the 316L stainless steel powder in Examples 1 to 3, respectively, and the corresponding sintered parts were produced under the same process flow.

[0081] Please refer to Figure 4 As shown, from left to right, the metallographic images of SKH-9 mold steel sintered parts produced using the binders obtained in Examples 1 to 3 are all low porosity. Obviously, the SKH-9 mold steel sintered part produced using the binder of Example 3 has the lowest porosity, and its density reaches 98.9% as measured by Archimedes' drainage method.

[0082] Please refer to Figure 5 As shown, from left to right, the metallographic images of M2 tool steel sintered parts produced using the binders obtained in Examples 1 to 3 are shown. It is clear that the M2 tool steel sintered part produced using the binder of Example 3 has the lowest porosity, and its density reaches 91.7% as measured by Archimedes' drainage method.

[0083] As can be seen from the above embodiments, the binder provided by the present invention meets the requirements of binder spray additive manufacturing. By further using a base material with a wider molecular weight distribution, the forming quality, surface morphology, and density can be improved. Furthermore, by adding anhydrous copper acetate to the binder, the forming quality, surface morphology, and density can be significantly improved. The principle is that during the heating process, copper acetate reacts to generate nano-copper particles, which are distributed in the blank to achieve the effect of homogenizing the sintering temperature. Moreover, copper has a low melting point and has an instantaneous liquid phase, which is conducive to the movement of powder particles and can significantly improve the density of the sintered parts.

Claims

1. An adhesive for adhesive spraying additive manufacturing, characterized in that, The adhesive comprises the following components in parts by weight: 10-15 parts base material, 5-10 parts ethylene glycol, 5-10 parts ethylene glycol monobutyl ether, 5-10 parts 2-pyrrolidone, 60-70 parts deionized water, 1-5 parts anhydrous copper acetate, and 0.01-5 parts metal-organic framework materials (MOFs).

2. The adhesive according to claim 1, characterized in that: The base material is polyvinylpyrrolidone with an average molecular weight of 40,000.

3. The adhesive according to claim 1, characterized in that: The base material is obtained by uniformly mixing polyvinylpyrrolidone with different average molecular weights, with an average molecular weight range of 10,000 to 100,000.

4. The adhesive according to claim 3, characterized in that: The base material is obtained by mixing polyvinylpyrrolidone with average molecular weights of 24,000, 40,000 and 58,000 in a mass ratio of 1:1:

1.

5. The adhesive according to claim 1, characterized in that: The metal-organic framework materials (MOFs) include Cu-MOF and Al-MOF.

6. The method for preparing an adhesive for adhesive spraying additive manufacturing according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Add ethylene glycol to deionized water at room temperature and stir for 5 minutes; (2) Add ethylene glycol monobutyl ether to the system obtained in step (1) and stir for 5 minutes; (3) Add 2-pyrrolidone to the system obtained in step (2) and stir for 5 minutes; (4) Add polyvinylpyrrolidone to the system obtained in step (3) and stir for 30 minutes; (5) Add metal-organic framework materials (MOFs) to the system obtained in step (4), stir for 30 minutes, then add anhydrous copper acetate and stir for 30 minutes.

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