A method for preparing a metal-ceramic composite powder and a printing method

Abstract

The application relates to a metal-ceramic composite powder preparation method, which comprises the following steps: performing surface activation treatment on metal powder, so that a high-activity interface is formed on the surface; performing hydroxylation treatment on ceramic powder and breaking agglomeration; under the condition of possessing shearing energy and / or controlling humidity, introducing the hydroxylated ceramic powder into the surface-activated metal powder, so that the ceramic powder is adsorbed or inlaid on the surface of the metal powder, and a composite powder with a stable interface coupling structure is formed. The application also relates to a metal-ceramic composite material printing method. The scheme can solve the problems of uneven mixing and easy layering of the metal and ceramic powder caused by the large difference in physical properties.

Description

Technical Field

[0001] This invention relates to the field of 3D printing methods, and in particular to a method for preparing and printing metal-ceramic composite powder. Background Technology

[0002] With the rapid development of additive manufacturing technology, binder jet 3D printing, due to its supportless operation, fast forming speed, and applicability to large-size and complex structural parts, provides a new path for moldless forming of metal-ceramic composite materials. These composite materials are in urgent demand in areas such as lightweighting and high-temperature resistance.

[0003] However, applying binder jetting technology to metal-ceramic systems first encounters a fundamental challenge: the significant differences in physical properties such as density, surface energy, and particle size between metal and non-metal ceramic powders. Composite powders prepared using conventional mechanical mixing methods are highly susceptible to gravitational segregation or centrifugal separation during transportation, powder spreading, and printing, resulting in severely uneven microstructure distribution in the powder bed and even the final green body. This unevenness not only directly affects the dimensional accuracy and surface quality of the formed parts but also leads to defects such as cracks, delamination, or insufficient densification due to localized shrinkage differences during subsequent debinding and sintering, severely restricting the structural reliability and performance consistency of metal-ceramic composite materials. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for preparing and printing metal-ceramic composite powders to address the problems of uneven mixing and easy stratification caused by the large differences in physical properties between metal and ceramic powders.

[0005] To solve the above problems, the present invention adopts the following technical solution: In a first aspect, embodiments of the present invention disclose a method for preparing metal-ceramic composite powder, comprising: Surface activation treatment is performed on metal powder to form a highly active interface on its surface; Hydroxylation treatment of ceramic powder to break down agglomerates; Under conditions of shear energy and / or controlled humidity, the hydroxylated ceramic powder is introduced into the surface-activated metal powder, so that the ceramic powder is adsorbed or embedded on the surface of the metal powder to form a composite powder with a stable interfacial coupling structure.

[0006] In one embodiment, the surface activation treatment includes plasma activation or vacuum low-temperature annealing to remove oxide films and oil stains from the surface of the metal powder.

[0007] In one embodiment, before or after introducing ceramic powder into metal powder, a step of surface modification of the metal powder using a silane coupling agent is included, wherein the amount of silane coupling agent added is 0.5%-2% of the mass of the metal powder.

[0008] In one embodiment, the hydroxylation treatment includes: placing ceramic powder in deionized water and ultrasonically treating it for 10-40 minutes.

[0009] In one embodiment, after the hydroxylation treatment, the ceramic powder is subjected to air jet milling to break up agglomerates.

[0010] In one embodiment, the mass ratio of the metal powder to the ceramic powder is (5–95%):(95–5%).

[0011] Secondly, embodiments of the present invention disclose a method for printing metal-ceramic composite materials, applied to the metal-ceramic composite powder preparation method described above, comprising: The prepared composite powder is laid on a printing powder bed, and the powder temperature of the powder bed is controlled at 34-36℃ during the powder laying and printing process. Adhesive jet printing is performed on the powder bed, with a printing layer thickness of 100-150μm, and the layers are stacked one by one to form a green body; After the green blank is printed, multiple layers of composite powder are laid on top of it to form a powder-embedded layer; The green body with the embedded powder layer is subjected to stepwise heating and curing treatment.

[0012] In one embodiment, the powder temperature in the area where the adhesive is sprayed during the printing process is controlled at 33-34°C.

[0013] In one embodiment, the stepwise heat curing process includes: First stage: Increase the temperature to 50-100℃ at a rate of 1-5℃ / min and hold for 2-5 hours; Second stage: Increase the temperature to 140-180℃ at a rate of 2-6℃ / min and hold for 2-10 hours; It is then cooled in the furnace to below 60°C.

[0014] The technical solution adopted in this invention can achieve the following beneficial effects: The metal-ceramic composite powder preparation method disclosed in this invention can directly and effectively solve the problem of segregation that easily occurs during mixing and post-processing of metal and ceramic powders due to their vastly different physical properties such as density and surface energy. Surface activation of the metal powder and hydroxylation treatment of the ceramic powder create interfacial conditions for a tight bond between the two. Under controlled mixing, the ceramic powder is directionally adsorbed onto the surface of the metal powder, forming stable composite particles. This structure improves the uniformity, flowability, and powder-laying stability of the mixed powder, enabling the powder to form a dense and uniform layer in the printing bed, laying a material foundation for obtaining high-precision green bodies. Furthermore, by adjusting the activation and coupling methods, this method has broad applicability to various material systems, not only suitable for combinations of common metals (aluminum, steel, copper) and ceramics (oxides, nitrides), but also providing ideas for the preparation of a wider range of heterogeneous material composite powders. Attached Figure Description

[0015] none Detailed Implementation

[0016] This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention.

[0017] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," "top," "bottom," "end," "top," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] This invention discloses a method for preparing metal-ceramic composite powder, which specifically includes: Surface activation treatment is performed on metal powder to form a highly active interface on its surface. At this time, the purpose of surface activation treatment on metal powder is to remove the oxide layer and contaminants on its surface, so that its surface can be improved and a highly active interface rich in active sites (such as hydroxyl groups) can be formed.

[0020] The ceramic powder is subjected to hydroxylation treatment to break up agglomerates. Specifically, the ceramic powder is placed in deionized water and subjected to ultrasonic treatment. The ultrasonic cavitation effect promotes the reaction between the surface and water, generating a large number of hydroxyl groups (-OH), thereby improving the surface hydrophilicity and reactivity. Subsequently, an air jet milling step is usually followed to break up agglomerates that exist in the powder during wet treatment or in the powder itself, ensuring the dispersion of the powder.

[0021] Under conditions of shear energy and / or controlled humidity, the hydroxylated ceramic powder is introduced into the surface-activated metal powder, causing the ceramic powder to adsorb or embed onto the metal powder surface, forming a composite powder with a stable interfacial coupling structure. In this process, shear force promotes uniform dispersion and close contact between the powder particles, while suitable humidity facilitates interfacial interactions. Ultimately, the ceramic powder can be firmly bonded to the metal powder surface through physical adsorption or partial mechanical embedding, forming a metal-ceramic composite powder with a stable interfacial coupling structure.

[0022] In the above method, the metal powder is activated to "renew" its surface, while the ceramic powder is "energized" through hydroxylation. When the two meet under controlled shear and humidity conditions, the newly formed hydroxyl groups on the ceramic powder surface generate strong interaction forces with the highly active surface of the activated metal powder. Shear energy ensures that the powders are fully and uniformly contacted throughout the mixing volume, preventing rapid stratification due to density differences; while humidity control can regulate interfacial energy, promoting the stable adsorption process. In this method, ceramic particles do not simply mix mechanically with metal particles, but tend to preferentially adhere to the area around the metal particles, forming a "core-shell" or tightly wrapped microstructure. This structure fundamentally inhibits the separation (segregation) of the ceramic and metal phases due to inertial differences during subsequent transportation, powder spreading, and other dynamic processes, providing a highly uniform and fluid composite powder material for subsequent 3D printing processes.

[0023] As described above, the metal-ceramic composite powder preparation method disclosed in this invention can directly and effectively solve the problem of easy segregation between metal and ceramic powders during mixing and post-processing due to significant differences in physical properties such as density and surface energy. Surface activation of the metal powder and hydroxylation treatment of the ceramic powder create interfacial conditions for close bonding. Under controlled mixing, the ceramic powder is directionally adsorbed onto the surface of the metal powder, forming stable composite particles. This structure improves the uniformity, flowability, and powder-laying stability of the mixed powder, enabling the powder to form a dense and uniform layer in the printing powder bed, laying a material foundation for obtaining high-precision green bodies. Furthermore, by adjusting the activation and coupling methods, this method has broad applicability to various material systems, not only applicable to combinations of common metals (aluminum, steel, copper) and ceramics (oxides, nitrides), but also providing ideas for the preparation of a wider range of heterogeneous material composite powders.

[0024] Furthermore, the surface activation treatment includes plasma activation or vacuum low-temperature annealing to remove oxide films and oil stains from the surface of the metal powder. Plasma activation efficiently and cleanly etches the metal powder surface and introduces active groups; vacuum low-temperature annealing effectively removes adsorbed oil stains and some oxide films while avoiding excessive sintering of the powder. Both methods enhance the chemical activity and cleanliness of the metal powder surface, providing a more ideal and consistent interfacial basis for subsequent bonding with ceramic powders or coupling agents, thereby ensuring the quality and stability of the composite powder interfacial coupling structure.

[0025] Furthermore, before or after introducing the ceramic powder into the metal powder, a step of surface modification of the metal powder using a silane coupling agent is included, wherein the amount of the silane coupling agent added is 0.5%-2% of the metal powder mass. The silane coupling agent molecule has an amphiphilic structure; one end (e.g., an alkoxy group) can bind to hydroxyl groups on the metal surface after hydrolysis, while the other end (an organic functional group) can react with hydroxyl groups or other groups on the ceramic surface. This step constructs a chemical "bridge" between the metal and ceramic, greatly enhancing the bonding force between the heterogeneous materials. Compared to pure physical adsorption, this chemical bonding makes the resulting composite powder more stable under vibration and powder spreading shear forces, and the interfacial coupling structure is less likely to be destroyed, further ensuring the uniformity and reliability of the composite powder composition.

[0026] Furthermore, the hydroxylation treatment includes: ultrasonic treatment of the ceramic powder in deionized water for 10-40 minutes. During this process, ultrasonic treatment generates a strong cavitation effect and mechanical vibration, forcing the deionized water to fully contact and react with the ceramic powder surface, rapidly and efficiently introducing hydroxyl groups; it also effectively breaks up soft agglomerates of the powder. The limited time range (10-40 minutes) ensures the hydroxylation reaction proceeds fully, while avoiding excessive powder refinement or low process efficiency that may result from excessive time. This represents an efficient and controllable process parameter for achieving uniform and highly active modification of the ceramic powder surface.

[0027] Furthermore, after the hydroxylation treatment, the ceramic powder is subjected to air jet milling to break up agglomerates. While ultrasonic treatment can break up most agglomerates, wet treatment may cause the fine particles to re-agglomerate. Air jet milling uses high-speed airflow to cause powder particles to collide and rub against each other, which can thoroughly break up residual hard and soft agglomerates, ensuring that each ceramic powder particle exists in a monodisperse or near-monodisperse state. This allows the ceramic powder to be more uniformly distributed and adsorbed when subsequently mixed with metal powder, eliminating localized compositional unevenness caused by the presence of agglomerates.

[0028] Furthermore, the mass ratio of the metal powder to the ceramic powder is (5–95%):(95–5%). The proportion of metal to ceramic can be freely adjusted within this range, thereby allowing for the customized preparation of a series of composite materials with varying properties. This enables the method described in this invention not only to be used for preparing structural components but also to provide material preparation possibilities for manufacturing functional devices with specific functional gradients or functional regions.

[0029] Based on the metal-ceramic composite powder preparation method disclosed in the embodiments of the present invention, the present invention also discloses a metal-ceramic composite material printing method, applied to the metal-ceramic composite powder preparation method described in any of the above embodiments. The disclosed metal-ceramic composite material printing method includes: The prepared composite powder is laid on a printing powder bed. During the powder laying and printing process, the powder temperature of the powder bed is controlled at 34-36℃. Adhesive jet printing is performed on the powder bed, and the printing layer thickness is 100-150μm. The layers are stacked one by one to form a green body. After the green body is printed, multiple layers of composite powder are laid on top to form a powder-embedded layer. The green body with the powder-embedded layer is subjected to stepwise heat curing treatment.

[0030] The process begins with laying a uniform composite powder layer under temperature control (34-36℃). This temperature is a balance point designed to address the differences in thermal properties between metal and ceramic, satisfying the required drying rate for the ceramic phase while preventing premature localized drying of the binder due to excessively rapid thermal conductivity in the metal phase. A relatively large printing layer thickness of 100-150μm increases the longitudinal penetration depth of the binder while reducing its lateral capillary diffusion, effectively suppressing ink bleeding and improving the clarity of the formed contour. The powder layer covering the printed area acts as a "thermal buffer layer" and "pressure homogenization layer" in the subsequent curing oven, ensuring that all surfaces of the green body are in a nearly uniform thermal and pressure environment, alleviating thermal stress caused by excessively rapid evaporation rates on the top free surface and uneven heating at the bottom. The subsequent stepwise heating and curing process (such as low-temperature dehumidification followed by high-temperature curing) removes the solvent and promotes resin polymerization in a gentle and controlled manner, avoiding uneven binder migration, phase separation or stress cracking caused by excessively rapid heating or local temperature differences, and finally obtaining a complete green body without macroscopic defects.

[0031] Specifically, firstly, by precisely controlling the powder bed temperature at 34-36℃, the different requirements of metal and ceramic for binder drying behavior are cleverly balanced, reducing the risks of "powder pushing" and "ink bleeding" from the source. Secondly, using a larger layer thickness of 100-150μm not only accommodates the slightly increased powder particle size after pretreatment, but more importantly, utilizes its thermal buffering and flow-limiting effects to further stabilize the printing process and improve dimensional accuracy. Next, the combination of "embedded powder thermal field homogenization curing technology" and "stepwise heating curing" process is the core to prevent defects such as cracks and warping in the green body during the curing stage. The embedded powder layer creates a uniform microenvironment, and stepwise curing provides a window for slow stress release. Both ensure that the heterogeneous interface between the metal and ceramic can deform in a coordinated manner during binder curing shrinkage and thermal expansion, thereby obtaining a high-quality green body with a complete structure and strength that meets the requirements of subsequent debinding and sintering.

[0032] Furthermore, the powder temperature in the area where the adhesive is sprayed during the printing process is controlled at 33-34°C. This temperature is sufficient to accelerate the appropriate spreading and penetration of water-based or alcohol-based adhesives on the surface of ceramic particles, forming a good bridge, while preventing the adhesive from evaporating and drying out too quickly around the metal particles due to excessive temperature. This achieves balanced and stable wetting of both metal and ceramic particles by the adhesive at the microscale.

[0033] Furthermore, the stepwise heat curing process includes: The first stage involves heating to 50-100℃ at a rate of 1-5℃ / min and holding for 2-5 hours. The second stage involves heating to 140-180℃ at a rate of 2-6℃ / min and holding for 2-10 hours, followed by furnace cooling to below 60℃. In the first stage, the slower heating rate (1-5℃ / min) to the medium-low temperature range (50-100℃) and prolonged holding (2-5 hours) gently removes most of the solvent or moisture from the binder, allowing the binder network to initially form while maintaining its flexibility, preventing pores or cracks caused by violent vaporization. The second stage involves a slightly faster heating rate (2-6℃ / min) to a higher temperature (140-180℃) and holding for 2-10 hours, aiming to fully cross-link and cure the binder resin (such as phenolic resin, furan resin, etc.) to achieve maximum strength. This "slow first, then fast; low first, then high" curing path follows the objective laws of material reaction, achieving a stable and controllable increase in green strength and releasing thermal stress to the greatest extent.

[0034] The following are specific implementation examples: Example: Adhesive spraying molding of a silicon-aluminum composite material This embodiment uses aluminum alloy powder (6061) and silicon dioxide (SiO2) powder as raw materials to specifically illustrate the implementation process of the present invention.

[0035] 1. Pretreatment of metal-ceramic composite powder 6061 aluminum alloy powder with a D50 (median particle size) of 10 μm and SiO2 powder with a D50 of 30 μm were selected. First, the aluminum alloy powder underwent vacuum low-temperature annealing: held at 120°C for 2 hours, followed by furnace cooling to room temperature. This step aims to effectively remove the oxide film and adsorbed organic contaminants from the aluminum powder surface, thereby improving its surface activity.

[0036] Subsequently, 0.5% (by weight) of silane coupling agent (KH560) was added to the treated aluminum powder, and the mixture was stirred at a low speed of 70 rpm to ensure that the coupling agent uniformly covered the surface of the aluminum powder. Simultaneously, the SiO2 powder was placed in deionized water and subjected to ultrasonic treatment for 30 minutes to achieve hydroxylation of the powder surface. After ultrasonication, the slurry was immediately subjected to air-jet milling and drying to break up any potential secondary agglomerates, obtaining highly active and well-dispersed SiO2 powder. Finally, the two pretreated powders were placed in a planetary ball mill in a certain proportion and mixed using a dry mixing method at a speed of 150 rpm for 1 hour to obtain a homogeneous "silicon-aluminum" composite powder.

[0037] 2. Adhesive jet printing of silicon-aluminum green blanks The prepared silicon-aluminum composite powder was loaded into a binder jet 3D printer. High-frequency vibration technology was used during powder spreading to increase the packing density of the powder bed. A water-based binder was used for printing. Multiple comparative experiments were conducted to determine the optimal printing parameters; the specific parameters and green state are shown in Table 1.

[0038] Table 1 Comparison of green state under different printing process parameters Experiment number Printed layer thickness (μm) Temperature of powder surface during powder application (°C) Powder temperature during printing (°C) Macroscopic state of green blank 1 80 31.0 30.3 The bottom is severely ink-bleeding, and the outline is blurred. 2 100 33.4 32.0 Slight ink bleeding at the bottom 3 120 35.5 34.8 No ink seepage at the bottom, clear green body boundaries 4 80 35.0 - The powder is noticeably being pushed up, making normal printing impossible. Comparative analysis shows that using a larger printing layer thickness of 120μm and controlling the powder temperature during powder spreading and printing within narrow ranges of 35-36°C and 33-34°C respectively can effectively balance the penetration behavior of the binder between the metal and ceramic powders. This parameter combination avoids excessive lateral diffusion of the binder ("ink bleeding") caused by excessively low temperatures, and also prevents premature local drying of the binder ("powder pushing") caused by excessively high temperatures and rapid thermal conductivity of the metal powder, thus obtaining a green body with high dimensional accuracy and clear contours.

[0039] 3. Powder-embedded thermal field homogenization and green curing After the green compact is printed, it is not removed immediately. Instead, the powder bed continues to descend and lay 10 layers of the same "silicon-aluminum" composite powder, completely covering the green compact. This "powder-embedded layer" provides a uniform thermal environment and pressure field for the green compact during subsequent curing. The curing process uses a two-step method: first, the temperature is increased to 70°C at a rate of 1°C / min and held for 2 hours; then, the temperature is increased to 150°C at a rate of 2°C / min and held for 6 hours; finally, the temperature is cooled to below 60°C in the furnace.

[0040] To verify the necessity of the "powder embedding" step, a comparative experiment was set up, and the results are shown in Table 2.

[0041] Table 2 Comparison of green body curing states under different post-processing techniques Experiment number Curing process Operations after printing Green state after curing A Keep warm at 70°C for 2 hours, and at 150°C for 6 hours. Direct curing (without powder embedding) Irregular cracks appeared on the surface of the green body B Keep warm at 70°C for 2 hours, and at 150°C for 6 hours. First, apply 10 layers of powder, then proceed with curing. The green body is intact and has no visible cracks. The comparative results show that, without powder embedding, the green body, during curing, suffers from significant internal stress due to uneven moisture evaporation and binder curing rates caused by direct exposure of the top to hot air. This, coupled with the difference in thermal expansion coefficients between the metal and ceramic, ultimately leads to cracking. However, by employing the powder embedding technology described in this invention, the green body is placed in a uniform microenvironment, effectively buffering and homogenizing thermal stress, thus successfully preparing a structurally intact, crack-free silicon-aluminum composite green body.

[0042] Finally, the work box is moved to the powder cleaning station to remove excess powder from the surface and internal pores of the green body, thus obtaining a high-quality metal-ceramic composite green body that can be used for subsequent degreasing and sintering.

[0043] In summary, this embodiment demonstrates that the composite powder pretreatment method, optimized printing parameters (specific temperature range and large layer thickness), and embedded powder thermal field homogenization curing technology of the present invention can effectively solve key problems such as powder segregation, printing defects (ink penetration, powder pushing) and curing cracking encountered when forming metal-ceramic composite materials using binder spraying technology, and successfully achieve the synergistic forming of heterogeneous materials.

[0044] The embodiments described above 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 patent. 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, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing metal-ceramic composite powder, characterized in that, include: Surface activation treatment is performed on metal powder to form a highly active interface on its surface; Hydroxylation treatment of ceramic powder to break down agglomerates; Under conditions of shear energy and / or controlled humidity, the hydroxylated ceramic powder is introduced into the surface-activated metal powder, so that the ceramic powder is adsorbed or embedded on the surface of the metal powder to form a composite powder with a stable interfacial coupling structure.

2. The method for preparing metal-ceramic composite powder according to claim 1, characterized in that, The surface activation treatment includes plasma activation or vacuum low-temperature annealing to remove oxide films and oil stains from the surface of the metal powder.

3. The method for preparing metal-ceramic composite powder according to claim 1, characterized in that, Before or after introducing ceramic powder into metal powder, the method further includes a step of surface modification of the metal powder using a silane coupling agent, wherein the amount of the silane coupling agent added is 0.5%-2% of the mass of the metal powder.

4. The method for preparing metal-ceramic composite powder according to claim 1, characterized in that, The hydroxylation treatment includes: placing ceramic powder in deionized water for ultrasonic treatment for 10-40 minutes.

5. The method for preparing metal-ceramic composite powder according to claim 4, characterized in that, After the hydroxylation treatment, the ceramic powder is subjected to air jet milling to break up agglomerates.

6. The method for preparing metal-ceramic composite powder according to claim 1, characterized in that, The mass ratio of the metal powder to the ceramic powder is (5–95%):(95–5%).

7. A method for printing metal-ceramic composite materials, applied to the metal-ceramic composite powder preparation method described in claims 1 to 6, characterized in that, include: The prepared composite powder is laid on a printing powder bed, and the powder temperature of the powder bed is controlled at 34-36℃ during the powder laying and printing process. Adhesive jet printing is performed on the powder bed, with a printing layer thickness of 100-150μm, and the layers are stacked one by one to form a green body; After the green blank is printed, multiple layers of composite powder are laid on top of it to form a powder-embedded layer; The green body with the embedded powder layer is subjected to stepwise heating and curing treatment.

8. The metal-ceramic composite material printing method according to claim 7, characterized in that, The powder temperature in the area where the adhesive is sprayed during the printing process is controlled at 33-34℃.

9. The method for printing metal-ceramic composite materials according to claim 7, characterized in that, The stepwise heat curing process includes: First stage: Increase the temperature to 50-100℃ at a rate of 1-5℃ / min and hold for 2-5 hours; Second stage: Increase the temperature to 140-180℃ at a rate of 2-6℃ / min and hold for 2-10 hours; It is then cooled in the furnace to below 60°C.