Preparation method of novel epoxy resin coated metal or ceramic powder

Abstract

The invention discloses a preparation method of novel epoxy resin coated metal or ceramic powder. The method comprises the following steps: firstly, putting epoxy resin powder into an acetone solvent, and stirring to fully dissolve epoxy resin in acetone to obtain an epoxy resin acetone solution; adding metal powder, ceramic powder or composite powder composed of ceramic / metal into the epoxy resin acetone solution, and stirring to enable the powder to be in full contact with the solution; filtering through a screen to remove the liquid or taking out the wetted powder through a filter spoon to obtain wet powder of which the surface is coated with a small amount of epoxy resin acetone solution; and drying the wet powder, grinding, crushing and screening to obtain the epoxy resin coated metal or ceramic powder. Compared with a traditional dissolution evaporation method, the method has the advantages that the link of heating, stirring and evaporating the solvent is omitted, the coating uniformity is improved, meanwhile, the preparation process is simpler, the requirement for equipment is lower, the preparation cost of the coating powder can be remarkably reduced, and industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of material preparation technology in additive manufacturing, specifically to a novel method for preparing epoxy resin-coated metal or ceramic powder. Background Technology

[0002] Traditional subtractive manufacturing processes, such as casting, forging, and rolling, face challenges in fabricating components with complex internal structures (such as internal flow channels). Additive manufacturing (AM), a material processing technology distinct from traditional subtractive manufacturing, is based on the principle of layer-by-layer stacking to form components. It offers a high degree of freedom in material design and manufacturing, enabling the fabrication of components with virtually any complex shape. Therefore, in recent years, additive manufacturing (AM) technology has received increasing attention and research in the fabrication of complex metal components and has already found practical applications in aerospace, automotive, and medical fields.

[0003] Selective Laser Sintering (SLS) is a type of powder bed fusion additive manufacturing technology. It can be used for the direct forming of polymer materials as well as the indirect forming of metals or ceramics. SLS indirect forming of metals or ceramics uses a low-power laser as an energy source to melt a polymer binder to bond metal or ceramic powders, resulting in a green part with a certain strength. Subsequent debinding and sintering processes then bring the part to the required density and strength.

[0004] There are two methods for preparing composite powders composed of polymer binders and metal or ceramic powders used in SLS: mechanical mixing and coating. Mechanical mixing involves mixing metal or ceramic powders and polymer binder powders using a ball mill, V-type mixer, or other mixer to obtain a composite powder. While the mechanical mixing method is the simplest, it also has drawbacks such as difficulty in uniformly mixing the polymer binder, easy agglomeration, high binder content, and low green strength. Coating, on the other hand, uses physicochemical methods to coat the surface of metal or ceramic particles with polymer binders, forming polymer-coated metal or ceramic composite powders. Coating results in lower binder content, higher green strength, better laser absorption, and, most importantly, better polymer stability in the composite powder, making agglomeration less likely. Currently, three main coating methods are commonly used: spray drying, melt-crushing, and dissolution-precipitation. Among these, spray drying requires sophisticated equipment and is more expensive. The melt-crush method requires heating the polymer binder until it is completely melted, and then adding the metal or ceramic powder into the molten polymer binder to achieve resin coating of the metal or ceramic powder. However, because the amount of binder added is extremely small (e.g., only 1.5% by mass), the coating effect is poor, making it difficult to effectively coat the metal or ceramic powder. The dissolution-precipitation method involves dissolving the resin binder in an organic solvent, which is equivalent to increasing the volume of the binder, thus allowing for more effective coating of metal and ceramic powders, and is therefore more widely used. The traditional dissolution-precipitation method for preparing coated powder mainly includes solution preparation (using an organic solvent to dissolve the polymer binder), stirring and evaporating the organic solvent, drying, and crushing and sieving. Among these steps, the stirring and evaporating of the organic solvent needs to be carried out at low or room temperature to prevent the solvent from evaporating too quickly, and stirring is also required to achieve homogenization of the solute. However, the stirring and evaporation process of organic solvents still has two drawbacks: first, the process is relatively complex; second, during the stirring and evaporation of organic solvents, it is difficult to effectively homogenize the solute epoxy resin, especially in the final stage of evaporation, when there is less solution and a large amount of metal or ceramic powder is deposited at the bottom of the container. This results in a certain degree of unevenness in the coating of the resin on the metal or ceramic powder, which in turn has a certain adverse effect on the subsequent forming and sintering process. Summary of the Invention

[0005] Based on the shortcomings of the traditional dissolution-precipitation method for preparing coated powder, the purpose of this invention is to provide a novel method for preparing epoxy resin coated metal or ceramic powder suitable for selective laser sintering (SLS), which addresses the shortcomings of the traditional dissolution-precipitation method in terms of process complexity and poor coating uniformity.

[0006] This invention provides a novel method for preparing epoxy resin-coated metal or ceramic powder, which can be named the filtration-drying method. The specific steps are as follows:

[0007] (1) At room temperature, a certain proportion of solid epoxy resin powder is added to acetone and stirred for a period of time to allow the epoxy resin to fully dissolve in the acetone, thereby obtaining an acetone solution with a certain epoxy resin concentration. Among them, epoxy resin is the solute and acetone is the solvent; the mass ratio of epoxy resin to acetone is 1:(1.5~49); the stirring time should be determined according to the ambient temperature and the proportion of epoxy resin added, with the standard being that the epoxy resin is fully dissolved in acetone and there is no solid precipitate. The stirring time can be appropriately extended to allow the epoxy resin to be fully dissolved and dispersed; the epoxy resin is solid at room temperature and has a softening point ≥40℃. The epoxy resin is epoxy resin E06, epoxy resin E10, epoxy resin E12, epoxy resin E14, or epoxy resin E20.

[0008] (2) Add metal powder, ceramic powder, or a composite powder of metal and ceramic to an epoxy resin acetone solution and stir for a period of time to ensure sufficient contact between the powder and the solution. The amount of powder added to the epoxy resin acetone solution should be such that the powder is below the solution surface. During stirring, ultrasonic vibration can be performed simultaneously to ensure sufficient contact between the powder and the epoxy resin acetone solution. The metal powder includes pure metals and alloy powders, such as stainless steel, mold steel, nickel alloys, titanium alloys, aluminum alloys, or copper powder. The ceramic powder is silicon nitride, silicon carbide, titanium carbide, or alumina powder. The powder includes a mixture of the above-mentioned metals and ceramics. The average particle size of the metal or ceramic powder is ≤75μm.

[0009] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface.

[0010] (4) The wet powder is dried naturally at room temperature or heated and then ground, crushed and sieved to obtain epoxy resin coated metal, ceramic or ceramic / metal composite powder. The average particle size of the coated metal or ceramic powder is ≤75μm. The drying temperature does not exceed the decomposition temperature of epoxy resin.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) Compared with spray drying, the present invention has lower equipment requirements and lower production costs;

[0013] (2) Compared with the traditional dissolution-precipitation method (also known as the stirring-evaporation method), this invention reduces the preparation process, simplifies the process, and lowers equipment requirements, thus resulting in lower production costs. Furthermore, since there is no heating, stirring, or solvent evaporation step, the solution containing epoxy resin (solute) directly adheres to the surface of the solid powder. After drying and evaporating the organic solvent, the uniformity of epoxy resin coating on the powder is further improved, which in turn benefits the subsequent sintering process of the SLS-formed sample and improves the performance of the sintered body. The coated powder prepared in Examples 1-7 of this application, after SLS printing, degreasing, and sintering, can yield high-density metal or ceramic powder samples. Their density, yield strength, tensile strength, elongation, and Vickers hardness are all superior to those of samples prepared using the traditional dissolution-precipitation method (i.e., the stirring-evaporation method). Simultaneously, the carbon or oxygen content of the sintered sample prepared using the filtration-drying method of this invention as raw material at the same sintering temperature is significantly lower than that of the sintered sample prepared using the stirring-evaporation method at the same temperature. The significant reduction in carbon or oxygen content indicates that the filtration-drying method of this invention achieves a more uniform distribution of the coating resin. This improved uniformity of the coating resin distribution leads to a more uniform distribution of residual carbon in the degreased sample, resulting in a more complete reaction between carbon and oxides during subsequent sintering, thus reducing the carbon or oxygen content of the final sintered body. Simultaneously, the improved uniformity of carbon content distribution (meaning a more uniform distribution of alloying elements in the sample) also contributes to improved mechanical properties. Conversely, one reason for the improved mechanical properties of the sintered products obtained by the filtration-drying method can be attributed to the improved uniformity of epoxy resin distribution in the original coating powder. Detailed Implementation

[0014] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following provides a more detailed description of the invention. It should be noted that the specific embodiments described below are only for better explaining the invention, and the specific embodiments of the invention are not limited to the limited number described below. The invention is further described below with reference to specific embodiments of different epoxy resin-coated metal or ceramic powders prepared using this method.

[0015] Example 1: Epoxy resin E12 coating on 316L stainless steel powder

[0016] (1) At room temperature and pressure, epoxy resin E12 powder and acetone are added into a beaker at a mass ratio of 1:5. After stirring for 20 minutes, the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution.

[0017] (2) Add 600g of 316L stainless steel powder with a particle size of 15~53μm to 200ml of epoxy resin acetone solution and stir for 5 minutes to make the metal powder fully contact the solution.

[0018] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0019] (4) The wet powder is heated and dried at 180°C for 1 hour, then ground and crushed, and then sieved through a 200-mesh standard sieve to obtain epoxy resin coated 316L powder with an average particle size of less than 75μm.

[0020] The obtained epoxy resin-coated 316L powder was SLS-printed into a green body, degreased, and sintered to obtain a high-density sintered sample. The density, yield strength, tensile strength, elongation, and Vickers hardness of the sintered sample reached 99.1%, 261.4 MPa, 572.4 MPa, 72.9%, and 140.9 HV1, respectively. Its comprehensive performance is better than that of the 316L stainless steel sample prepared by the traditional dissolution precipitation method (i.e., stirring evaporation method) (the corresponding density, yield strength, tensile strength, elongation, and Vickers hardness are 98.7%, 247.5 MPa, 554.6 MPa, 76.6%, and 124.7 HV1, respectively). Meanwhile, the carbon and oxygen contents of the sintered sample prepared by the filtration and drying method of the present invention as raw material at 1430℃ were 0.0034 wt.% and 0.0008 wt.%, respectively, which were significantly lower than the carbon and oxygen contents of the sintered sample prepared by the stirring evaporation method at the same temperature (corresponding to 0.0266 wt.% and oxygen: 0.0048 wt.%).

[0021] Example 2: Epoxy resin E10 coated 18Ni300 mold steel powder

[0022] (1) At room temperature and pressure, epoxy resin E10 powder and acetone are added into a beaker at a mass ratio of 1:8. After stirring for 18 minutes, the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution.

[0023] (2) Add 600g of 18Ni300 mold steel powder with a particle size of 10~45μm to 300ml of epoxy resin acetone solution and stir for 5 minutes to make the metal powder fully contact the solution.

[0024] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0025] (4) After the wet powder is heated and dried at 120°C for 2 hours, it is ground and crushed, and then sieved through a 250-mesh standard sieve to obtain epoxy resin coated 18Ni300 powder with an average particle size of less than 75μm.

[0026] Example 3: Epoxy resin E12 coated K418 nickel-based high-temperature alloy powder

[0027] (1) At room temperature, epoxy resin E12 powder and acetone are added into a beaker at a mass ratio of 1:10. Stir for 15 minutes to fully dissolve the epoxy resin in the acetone to obtain an epoxy resin acetone solution.

[0028] (2) Add 600ml of K418 nickel-based high-temperature alloy powder with a particle size of 5~30μm to 150ml of epoxy resin acetone solution and stir for 5 minutes to make the metal powder fully contact the solution.

[0029] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0030] (4) After the wet powder is dried by vacuum heating at 150°C for 1 hour, it is ground and crushed, and then screened through a 400-mesh standard sieve to obtain epoxy resin coated K418 powder with an average particle size of less than 75μm.

[0031] Example 4: Epoxy resin E14 coated TC4 titanium alloy powder

[0032] (1) At room temperature, epoxy resin E14 powder and acetone are added into a beaker at a mass ratio of 1:15. After stirring for 15 minutes, the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution.

[0033] (2) Add 500g of TC4 titanium alloy powder with a particle size of 15~53μm to 160ml of epoxy resin acetone solution and stir for 5 minutes to make the metal powder fully contact the solution.

[0034] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0035] (4) After the wet powder is dried by vacuum heating at 100°C for 3 hours, it is ground and crushed, and then sieved through a 200-mesh standard sieve to obtain epoxy resin coated TC4 powder with an average particle size of less than 75μm.

[0036] Example 5: Epoxy Resin E10 Coated Silicon Carbide Powder

[0037] (1) At room temperature, epoxy resin E10 powder and acetone are added into a beaker at a mass ratio of 1:35. After stirring for 15 minutes, the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution.

[0038] (2) Add 400g of silicon carbide powder with an average particle size of 2μm to 150ml of epoxy resin acetone solution and stir for 6min to make the powder and solution fully contact.

[0039] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0040] (4) After the wet powder is heated and dried at 180°C for 1.5 hours, it is ground and crushed, and then sieved through a 400-mesh standard sieve to obtain epoxy resin coated silicon carbide powder with an average particle size of less than 75μm.

[0041] Example 6: Epoxy Resin E12 Coated Titanium Carbide Powder

[0042] (1) At room temperature, epoxy resin E12 powder and acetone are added into a beaker at a mass ratio of 1:40. Stir for 15 minutes to fully dissolve the epoxy resin in the acetone to obtain an epoxy resin acetone solution.

[0043] (2) Add 400g of titanium carbide powder with an average particle size of 3μm to 300ml of epoxy resin acetone solution and stir for 5min to make the powder and solution fully contact.

[0044] (3) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0045] (4) After the wet powder is heated and dried at 170°C for 1 hour, it is ground and crushed, and then sieved through a 500-mesh standard sieve to obtain epoxy resin coated titanium carbide powder with an average particle size of less than 75μm.

[0046] Example 7: Epoxy resin E12 coated titanium carbide / 316L composite powder

[0047] (1) Titanium carbide (TiC) powder with an average particle size of 1 μm and 316L stainless steel powder with a particle size of 5-30 μm were added to a mixing bottle at a mass ratio of 1:99 and mixed. The ball-to-particle ratio was 2:1, the rotation speed was 43 r / min, and the mixing time was 10 hours.

[0048] (2) At room temperature, epoxy resin E12 powder and acetone are added into a beaker at a mass ratio of 1:45. After stirring for 10 minutes, the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution.

[0049] (3) Add 600g of uniformly mixed TiC / 316L composite powder to 200ml of epoxy resin acetone solution and stir for 8min to ensure that the powder and solution are in full contact.

[0050] (4) Remove the liquid by filtration through a sieve or take out the wetted powder with a filter spoon to obtain wet powder with epoxy resin acetone solution on the surface;

[0051] (5) After the wet powder is heated and dried at 180°C for 2 hours, it is ground and crushed, and then sieved through a 400-mesh standard sieve to obtain epoxy resin coated TiC / 316L composite powder with an average particle size of less than 75μm.

[0052] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, such as changing the type and proportion of organic solvents, binders, or metal and ceramic particles, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A novel method for preparing epoxy resin-coated metal or ceramic powder, characterized in that, Includes the following steps: S1. At room temperature, solid epoxy resin powder is added to the solvent acetone and stirred until the epoxy resin is fully dissolved in the acetone to obtain an epoxy resin acetone solution. S2, put metal powder, ceramic powder or composite powder composed of ceramic / metal into epoxy resin acetone solution, and stir to make the powder fully contact the epoxy resin acetone solution. S3, remove the liquid by filtration through a sieve or remove the powder from the solution using a filter spoon to obtain a wet powder with an epoxy resin acetone solution on the surface; S4, wet powder is dried naturally at room temperature or heated and then ground, crushed and sieved to obtain epoxy resin coated metal or ceramic powder.

2. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, In step S1, the mass ratio of epoxy resin to acetone is 1:1.5~49.

3. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, In step S2, the added powder is below the surface of the epoxy resin acetone solution.

4. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, The epoxy resin is solid at room temperature and has a softening point ≥40℃.

5. The method for preparing a novel epoxy resin metal or ceramic powder according to claim 1, characterized in that, The epoxy resin is epoxy resin E06, epoxy resin E10, epoxy resin E12, epoxy resin E14 or epoxy resin E20.

6. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, The metal or ceramic powder is one or more of stainless steel, mold steel, nickel alloy, titanium alloy, aluminum alloy, copper, silicon nitride, silicon carbide, titanium carbide, or aluminum oxide.

7. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, The average particle size of the metal or ceramic powder in step S2 is ≤75μm.

8. The method for preparing a novel epoxy resin-coated metal or ceramic powder according to claim 1, characterized in that, The average particle size of the coated metal or ceramic powder in step S4 is ≤75μm.