A method for producing a ceramic core coating

Abstract

The application provides a ceramic core coating preparation method which adopts an electron beam physical vapor deposition method (EB-PVD) to prepare a yttrium oxide columnar coating on the surface of a silicon-based ceramic core. The yttrium oxide columnar coating can be used as a support structure, significantly improves the high-temperature strength and high-temperature deformation resistance of the ceramic core matrix, has strong stability at high temperatures, does not react with the interface of the casting, the specific surface area of the coating is increased, the alkali solution can enter the matrix material to ensure that the core matrix is smoothly removed, and the coating prepared by the EB-PVD method has high uniformity, and the thickness of the coating is about 50 um, which does not affect the wall thickness of the casting.

Description

Technical Field

[0001] This invention belongs to the field of surface modification technology, and in particular relates to a method for preparing a columnar coating on a silicon-based ceramic core. Background Technology

[0002] The ceramic core is used to form the inner cavity of the hollow blade, and together with the outer mold and shell, it ensures the dimensional accuracy of the hollow blade. After casting, the ceramic core is completely removed by chemical etching. The ceramic core determines the surface quality and dimensional accuracy of the casting, so it is required that the ceramic core does not react with the molten metal during the casting process, and that it can be easily removed from the inner cavity of the casting after casting.

[0003] Currently, silicon-based ceramic cores are the main type used in the market. Silicon-based ceramic cores are characterized by low sintering temperature and easy core removal. Their main problems are low high-temperature strength and a tendency to react with molten metal at high temperatures. Currently, the industry mainly uses methods such as impregnation, coating, and brushing to prepare coatings on the surface of the silicon-based ceramic core substrate to solve these problems. However, the coating thickness and uniformity need improvement. This not only affects the accuracy of the casting wall thickness but also leads to further shrinkage of the coating after secondary firing, resulting in poor adhesion between the coating and the substrate. Summary of the Invention

[0004] In view of this, to overcome the shortcomings of existing silicon-based cores, this invention provides a method for preparing a coating on a silicon-based ceramic core. This method improves the high-temperature performance of the silicon-based ceramic core while ensuring the coating effect, and simultaneously avoids interfacial reactions between the silicon-based core and the high-temperature alloy. Specifically:

[0005] A method for preparing a ceramic core coating, comprising:

[0006] Step 1: Fabrication of a silicon-based ceramic core;

[0007] Step 2: Clean the surface of the silicon-based ceramic core with alcohol to ensure that the surface is free of contaminants;

[0008] Step 3: Prepare a yttrium oxide columnar coating on the surface of a silicon-based ceramic core using electron beam physical vapor deposition (EB-PVD);

[0009] Step 4: Heat treatment.

[0010] During high-temperature alloy casting, the alloy corrodes the core surface. Firstly, silicon-based cores lack sufficient high-temperature strength, frequently resulting in core breakage and leakage during casting, leading to scrapped castings. Secondly, as casting temperature increases, SiO2 and the high-temperature alloy are more prone to interfacial reactions, affecting the quality of the casting's internal cavity, and the casting wall thickness may not meet requirements. Yttrium oxide possesses excellent heat resistance, corrosion resistance, and high-temperature stability, and is currently widely used in titanium alloy casting; however, its difficulty in core removal limits its widespread application. Based on the above objectives and addressing current ceramic core coating issues, this invention designs a columnar yttrium oxide coating. Using this columnar coating as the surface structure enhances the high-temperature compressive strength and thermal deformation resistance of silicon-based cores. The columnar coating, by increasing the wetting angle, isolates silicon oxide from the high-temperature molten metal, eliminating interfacial reactions between the alloy and the core, and improving the surface quality of the casting cavity.

[0011] Furthermore, the yttrium oxide columnar coating has a thickness of 50 μm. The columnar structure of the coating significantly increases the specific surface area, allowing the alkali solution to penetrate the core during core removal, thus ensuring effective core removal. Therefore, this coating effectively improves the interfacial reaction problem of silicon-based cores and compensates for the core removal problem of yttrium oxide cores, broadening the application range of silicon-based core castings.

[0012] Furthermore, the coating material for the yttrium oxide columnar coating prepared by electron beam physical vapor deposition (EB-PVD) is a yttrium oxide target.

[0013] Furthermore, the process parameters for preparing yttrium oxide columnar coatings using electron beam physical vapor deposition (EB-PVD) are as follows: deposition rate 2–3 μm / min, substrate temperature to target melting point ratio 0.3–0.5, vacuum degree 6–8 Pa, and electron beam current intensity 1–2 A.

[0014] Furthermore, the temperature of the heat treatment process in step four is 1000℃, and the temperature is maintained for 3 hours.

[0015] The beneficial effects of this invention are as follows:

[0016] 1) Yttrium oxide columnar coating can serve as a support structure, significantly improving the high-temperature strength and high-temperature deformation resistance of the ceramic core substrate;

[0017] 2) Yttrium oxide columnar coatings exhibit strong stability at high temperatures and do not react with the castings at the interface;

[0018] 3) The use of a columnar coating structure increases the coating's specific surface area, which can accelerate the penetration of alkaline solution into the matrix material and ensure the smooth removal of the core matrix;

[0019] 4) The coating prepared by the EB-PVD method has high uniformity and a coating thickness of about 50 μm, which will not affect the wall thickness of the casting. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the yttrium oxide columnar coating of the present invention. Detailed Implementation

[0022] To improve the high-temperature performance of silicon-based cores, this invention utilizes yttrium oxide coating technology. Through material and structural design optimization, a yttrium oxide coating is prepared on the surface of the silicon-based ceramic core, thereby enhancing the high-temperature performance of the silicon-based ceramic core and avoiding interfacial reactions between the silicon-based core and high-temperature alloys, thus expanding the application fields of silicon-based core castings.

[0023] Example 1

[0024] (1) Prepare silicon-based ceramic core slurry by mixing 70% to 85% quartz glass powder, 2% to 8% cristobalite powder, and 10% to 25% mullite powder, and then prepare ceramic slurry with plasticizer accounting for 18% to 25%.

[0025] (2) Prepare silicon-based ceramic cores. Inject the prepared ceramic slurry into the core mold, fill the wet core with powder, and sinter at 1100℃~1150℃ for 3~8h.

[0026] (3) Clean the surface of the core after baking, ensuring there are no powder, impurities, or other issues.

[0027] (4) A Y2O3 columnar coating with a thickness of 50 μm was prepared on a silicon-based ceramic core. The Y2O3 columnar coating was prepared by EB-PVD method, and the target material was a Y2O3 wafer with a purity of 99%. The process parameters were: vacuum degree of 6 bar, deposition rate of 2 μm / min, substrate temperature to target melting point ratio of 0.4, and electron beam current intensity of 2 A.

[0028] (5) After the columnar coating is prepared, a heat treatment process is carried out at a temperature of 1000℃ for 3 hours.

[0029] The table below shows a comparison of the performance results of the ceramic core with added columnar coating in this embodiment and the ceramic core itself. It can be seen that the corresponding performance is greatly improved.

[0030]

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a ceramic core coating, characterized in that, Step 1: Fabrication of a silicon-based ceramic core; Step 2: Clean the surface of the silicon-based ceramic core with alcohol to ensure that the surface is free of contaminants; Step 3: A yttrium oxide columnar coating is prepared on the surface of a silicon-based ceramic core using electron beam physical vapor deposition (EB-PVD). The coating material is a yttrium oxide target, and the process parameters are: deposition rate 2~3 μm / min, substrate temperature to target melting point ratio 0.3~0.5, vacuum degree 6~8 Pa, and electron beam current intensity 1~2 A. Step 4: Heat treatment at 1000℃ for 3 hours.

2. The method of claim 1, wherein The thickness of the yttrium oxide columnar coating is 50 μm.

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