Additive manufacturing ceramic element and method for improving density of additive manufacturing ceramic element

Abstract

The invention provides an additive manufacturing ceramic element and a method for improving the compactness of the additive manufacturing ceramic element, and the method comprises the following steps: in a CAD modeling stage, reserving a reserved air hole leading to the interior of a CAD model element in the CAD model element, the reserved air hole being communicated with a micropore network and a small cavity; the binder is sprayed, a blank body is obtained, and the reserved air holes, the micropore network and the small cavities all extend to the surface of the blank body; and performing chemical vapor infiltration on the blank body to obtain the additive manufacturing ceramic element. The problems that the densification process of the element is blocked and the internal density of the element is low due to the fact that micropores in the surface of the ceramic element are closed in the chemical vapor infiltration process are solved, the density of the element can be improved through reserved air holes, the chemical vapor infiltration technology does not need to be improved, and only fine adjustment needs to be conducted on a CAD model in the modeling stage.

Description

Technical Field

[0001] The present application belongs to the field of additive manufacturing of ceramic materials, and more specifically, to a method for additively manufacturing ceramic components and improving their density. Background Art

[0002] There are currently a variety of ceramic material preparation technology routes based on additive manufacturing. This method is aimed at the ceramic additive manufacturing technology route of binder jetting combined with chemical vapor infiltration. The basic principle of binder jetting is: use a high-precision electronically controlled nozzle to perform directional and fixed-point spraying of the binder on a flattened powder bed, and form the ceramic embryo through layered bonding. The embryo obtained by this method has low density, and there are a large number of interconnected irregular microporous channels and small cavities (usually micrometers) inside, which present a sponge network. The density needs to be improved by using chemical vapor infiltration technology.

[0003] Chemical vapor infiltration is a material deposition preparation technology, usually used to deposit high melting point materials such as ceramic materials. Its basic principle is: driven by carrier gas, gaseous reactants enter the material through the micropores of porous materials, and produce chemical reactions under the stimulation of high energy environment (heat, light, plasma) to form solid products, which are deposited in the pores to increase the density of the material.

[0004] One of the technical difficulties faced by chemical vapor infiltration is how to avoid the inability to further improve the density due to the premature closure of surface pores. During the chemical vapor infiltration process, the gaseous reactants enter the interior of the component through the micropores driven by the carrier gas, and undergo chemical reactions in a high-energy environment to form solid products. However, as the solid products accumulate, the micropores near the surface close, making it impossible for the gaseous reactants to enter the interior of the component, so that the solid products can only continue to form on the surface of the component, but the density inside the component is still low.

[0005] In current experiments, the micropores are usually enlarged to extend the time for gaseous reactants to enter the components and improve the efficiency of chemical vapor infiltration. However, changing the size of the micropores places high demands on the preparation technology, which usually requires changing the preparation parameters of the pre-process to increase the size of the micropores, which brings about process complexity; and for large-sized components, the increase in the size of the micropores cannot effectively improve the defect that more reactive gases cannot enter the components, and the problem of low density inside large-sized components needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, the technical solution adopted in this application is: a method for improving the density of additively manufactured ceramic components, comprising the following steps:

[0007] During the CAD modeling stage, reserve air holes leading to the interior on the CAD model components, and the reserve air holes are in communication with both the micro-pore network and the small cavities;

[0008] Inject the binder to obtain a green body, and the reserve air holes, the micro-pore network, and the small cavities all extend to the surface of the green body;

[0009] Subject the green body to chemical vapor infiltration to obtain an additive manufacturing ceramic component.

[0010] As a possible design, the diameter of the reserve air holes is at least one order of magnitude larger than the diameter of the micro-pore network.

[0011] The beneficial effects of the method for improving the density of additive manufacturing ceramic components provided by this application are as follows:

[0012] 1. Solve the problems of hindered densification process of components and low internal density of components due to the closure of micro-pores on the surface of ceramic components during the chemical vapor infiltration process. By reserving air holes, the density of components can be improved without modifying the chemical vapor infiltration process, and only minor adjustments to the CAD model are required during the modeling stage.

[0013] 2. This technology is flexible and versatile, applicable to various chemical vapor infiltration processes that require reactive gases to enter the interior of components, without the need to modify the process, and is suitable for chemical vapor infiltration processes of various ceramics. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0015] Figure 1 Schematic structural diagram of the additive manufacturing ceramic component provided by the embodiment of this application;

[0016] Among them, each reference numeral in the figure:

[0017] 1 - matrix; 2 - micro-pore network, 3 - reserve air hole, 4 - small cavity. Detailed Embodiments

[0018] In order to make the technical problems, technical solutions, and beneficial effects to be solved by this application more clearly understood, the following further elaborates on this application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0019] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0020] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0021] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0022] Since the density of ceramic elements produced by existing processes is relatively low, affecting their performance, and existing improvement methods have not significantly improved their density, embodiments of the present invention provide a method for improving the density of additively manufactured ceramic elements, including the following steps:

[0023] S1. At the CAD modeling stage, reserve air holes leading to the inside on the CAD model element, and the reserve air holes are communicated with both the microporous network and the small cavity;

[0024] S2. Spray the binder to obtain a green body, and the reserve air holes, the microporous network, and the small cavity all extend to the surface of the green body;

[0025] S3. Chemically vapor infiltrate the green body to obtain an additively manufactured ceramic element.

[0026] The structure of the additively manufactured ceramic element obtained by the above method is as Figure 1 shown. The additively manufactured ceramic element includes a matrix 1, a microporous network 2, reserve air holes 3, and small cavities 4, where the reserve air holes 3 are communicated with both the microporous network 2 and the small cavities 4.

[0027] Both steps S2 and S3 are prior arts, and the equipment and gas sources involved in this process are also existing, so they will not be elaborated in detail here.

[0028] For components with a size greater than or equal to the centimeter level, they will face the problem of low internal density after chemical vapor infiltration. The microporous network 2 (with a diameter of about several to dozens of micrometers) exists in all directions of the component. Its morphology is irregular, and the diameter is not fixed, forming a sponge-like network distribution inside the component, forming a microporous network 2 and small cavities 4 throughout the inside of the component. The size of the small cavities is in the tens to hundreds of micrometer level. The reserved air holes are reserved air holes leading to the inside of the component on the component through changes to the CAD model during the CAD modeling stage before the binder jetting process. Their size is in the sub-millimeter level (diameter 0.1 mm - 0.5 mm, equivalent to 100 μm - 500 μm). The reserved air holes penetrate the component and are connected to the sponge-like microporous network and small cavities. The diameter, shape, and density of the reserved air holes can be adjusted through CAD modeling to adapt to the chemical vapor infiltration process of different parameters and substances.

[0029] After the component design is completed in the CAD modeling stage, reserved air holes leading directly to the inside of the component are reserved at appropriate positions, and then binder jetting is performed to obtain a green body, and the green body is subjected to chemical vapor infiltration to obtain the component. In the early stage of the chemical vapor infiltration process, the reactive gas enters the component through the micropores and reserved air holes. In the high-energy environment, the reactive gas undergoes a chemical reaction in the microporous network, reserved air holes, and small cavities, forming solid products and accumulating and filling them, increasing the density of the component. In the middle stage of the chemical vapor infiltration process, the micron-level openings on the surface of the component gradually close due to the accumulation of products and cannot provide a channel for the reactive gas to enter the component. Since the diameter of the reserved air holes is one order of magnitude higher than that of the micron-level pores and has not been filled with solid products, it can remain unobstructed, enabling the reactive gas to continuously enter the inside of the component. Moreover, the reserved air holes are connected to the microporous network and small cavities inside the component, providing more connection paths and promoting the accumulation of products. In the late stage of the chemical vapor infiltration process, as the solid products accumulate in the reserved air holes, the reserved air holes also gradually close, and the densification process of the component ends.

[0030] The method for improving the density of additive manufacturing ceramic components disclosed in the present invention does not impose new requirements on the preparation process, and the diameter and shape of the reserved air holes can be adjusted (such as conical), so that they close after densification without changing the overall structure and surface structure of the ceramic component.

[0031] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for improving the density of additively manufactured ceramic components, characterized in that: The method includes the following steps: During the CAD modeling stage, reserve air holes leading to the interior on the CAD model components, and the reserved air holes are both communicated with the micro-pore network and the small cavity; Inject the binder to obtain a green body, and the reserved air holes, the micro-pore network and the small cavity all extend to the surface of the green body; Chemically vapor infiltrate the green body to obtain an additive manufacturing ceramic component.

2. The method for improving the density of an additive manufacturing ceramic component according to claim 1, characterized in that: The diameter of the reserved air holes is at least one order of magnitude larger than the diameter of the micro-pore network.

3. An additive manufacturing ceramic component prepared by the method according to claim 1 or 2.

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