阅读说明：本技术 一种可量产的高纯SiC陶瓷涂层的低温常压烧结制备方法 (Low-temperature normal-pressure sintering preparation method of high-purity SiC ceramic coating capable of realizing mass production ) 是由 梅辉 赵钰 常鹏 成来飞 于 2020-04-23 设计创作，主要内容包括：本发明涉及一种可量产的高纯SiC陶瓷涂层的低温常压烧结制备方法,以涂层的形式应用于需要耐高温、抗氧化及耐腐蚀等防护性能的领域。其技术特征在于步骤为调配高纯SiC料浆、刷涂和低温无压烧结。本发明所提供的技术方案通过调控高纯SiC料浆配方来控制SiC涂层的纯度和烧结温度,实现高纯SiC涂层在1750～1800℃的常压烧结和工业化制备生产。本发明中高纯SiC的料浆配方及刷涂和烧结过程灵活可控,涂层与基体结合良好,无明显剥落和裂纹,工艺过程操作简单,耗时短,大幅度降低了成本。(The invention relates to a low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating capable of being produced in large quantity, which is applied to the field needing high-temperature resistance, oxidation resistance, corrosion resistance and other protective properties in the form of a coating. The method is technically characterized by comprising the steps of preparing high-purity SiC slurry, brushing and sintering at low temperature and no pressure. According to the technical scheme provided by the invention, the purity and sintering temperature of the SiC coating are controlled by regulating and controlling the formula of the high-purity SiC slurry, and normal-pressure sintering and industrial preparation production of the high-purity SiC coating at 1750-1800 ℃ are realized. The formula of the slurry of the high-purity SiC and the brushing and sintering processes are flexible and controllable, the coating is well combined with the matrix, obvious peeling and cracks do not exist, the technological process is simple to operate, the consumed time is short, and the cost is greatly reduced.)

1. A low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating capable of being massively produced is characterized by comprising the following steps:

step 1, preparing high-purity SiC slurry: dissolving high-purity SiC powder with the purity of more than or equal to 99% in ethanol and butanone, adding triethyl phosphate with the mass fraction of 2%, transferring the mixture to a ball milling tank, carrying out ball milling for 8-12 hours by using agate balls, continuously adding 3% by mass of polyvinyl butyral, 3% by mass of glycerol and dioctyl phthalate with the mixing ratio of 1:1, 5% by mass of high-purity Si powder and 2% by mass of boron carbide powder, and carrying out ball milling for 8-12 hours to form high-purity SiC slurry;

step 2, brushing: brushing the high-purity SiC slurry on the surface of the matrix, and drying at room temperature to form a precoating layer;

and 3, low-temperature pressureless sintering: and sintering the obtained precoat in an inert atmosphere at the heating rate of 2.5 ℃/min and the sintering temperature of 1750-1800 ℃, and naturally cooling to finish the low-temperature normal-pressure sintering of the high-purity SiC ceramic coating after preserving the heat for 2-3 hours.

2. The method for preparing the high-purity SiC ceramic coating capable of being massively produced by the low-temperature normal-pressure sintering according to claim 1, which is characterized in that: the mixing ratio of the ethanol to the butanone is 1: 1.

3. The method for preparing the high-purity SiC ceramic coating capable of being massively produced by the low-temperature normal-pressure sintering according to claim 1, which is characterized in that: the granularity of the high-purity SiC powder is 3-5 mu m and 500 nm.

Technical Field

The invention belongs to the field of silicon carbide (SiC) ceramic materials, and relates to a low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating capable of being produced in large quantity.

Background

The SiC ceramics are widely applied to the fields of aerospace, aviation, microelectronics, automobiles, laser, mining industry, atomic energy and the like due to high hardness, high abrasion resistance, high bending strength, excellent oxidation resistance, acid-base corrosion resistance and high-temperature mechanical property. The high-purity SiC coating plays an important role in high-temperature protection, oxidation resistance and corrosion resistance in the fields, and the higher the purity of the SiC coating is, the less pollution is caused by impurities under an extremely severe working condition, and the more excellent the protection performance is. At present, the preparation and use of low-cost industrialized high-purity SiC ceramic coatings are still in an exploration stage in China, and the problems of complex preparation process, expensive equipment, high sintering temperature of SiC coatings, difficulty in controlling purity and high cost consumption mainly exist.

The common preparation methods of SiC used as a protective coating include a solid infiltration method (embedding method), a sputtering method, a chemical vapor deposition method and a brushing method. For example, chinese patent CN 105948822a provides a method for preparing a SiC coating on the surface of a SiC-based composite material, silicon powder is embedded on the surface of a silicon carbide-based composite material, and a SiC coating is obtained by high-temperature heat treatment in an excessive carbon source; chinese patent CN 102373417A provides a method for preparing an antioxidant SiC coating on the surface of a graphite material, which adopts ultrahigh vacuum multifunctional magnetron sputtering coating equipment to prepare a silicon (Si) coating on the surface of the graphite material, and obtains the antioxidant SiC coating through vacuum heat treatment; chinese patent CN 105503270a provides a method for preparing SiC coatings by chemical vapor deposition and precursor dip cracking; chinese patent CN 107082651B provides a SiC coating prepared by a brushing method, which is divided into an inner coating and an outer coating, wherein the inner coating mainly comprises SiC powder and Si powder and is coated on the surface of a carbon-containing material, the outer coating mainly comprises silicified slurry and is coated on the surface of the inner coating, and the SiC coating is obtained by vacuum sintering. The SiC coating prepared by the solid infiltration method has no obvious interface with the matrix, so that the problem of unmatched thermal expansion coefficients of the matrix and the coating can be solved, but the problems of incompact coating, low purity, more impurities and complex preparation process exist, so that the use of the SiC coating is influenced; the SiC coating prepared by the sputtering method and the chemical vapor deposition method has good bonding degree with a substrate, has good process repeatability, can prepare a coating with uniform thickness on the surface of a large-area substrate material, but has expensive equipment, high production cost and complex process; the painting method forms the pre-coating layer by means of the surface bonding method, and then sinters the pre-coating layer into the functional coating layer, has simple and convenient process, low production cost, no need of special equipment and high operability, is suitable for the industrial production of the surface coating layer of the large-scale complex component, and has great advantages in industrial application compared with other methods.

Because SiC is a strong covalent bond compound with a basic crystal structure unit of Si-C tetrahedron, the covalent bond accounts for about 88 percent, the ionic bond accounts for 12 percent, the strong covalent bond property ensures that the SiC has low self-diffusion rate during sintering, the sintering driving force is small, enough energy is not easy to obtain to form a crystal boundary, and when a sintering aid is not added, the sintering temperature of the SiC is about 2100-2200 ℃, the requirements on equipment and a use environment are extremely high, and the industrial application of the SiC is limited. At present, various researches on sintering of SiC ceramic materials are carried out at home and abroad, and the sintering mainly comprises normal pressure sintering, hot pressing sintering and reaction sintering. The normal pressure sintering can be divided into solid phase sintering and liquid phase sintering, wherein the solid phase sintering generally uses carbon (C) or boron (B) as a sintering aid to promote the sintering densification of SiC under the normal pressure, the required temperature is over 2000 ℃, the liquid phase sintering is to introduce metal or metal oxide and the like to form liquid phase at high temperature to promote the sintering, and the required temperature is about 1800-1950 ℃. Hot pressing sintering, namely, pressurizing while sintering, generally introduces a sintering aid similar to normal pressure sintering, and is a rapid sintering preparation method of the conventional SiC ceramic. In the reactive sintering, molten silicon with reactivity is infiltrated into pores in a ceramic biscuit containing C under the action of capillary force, the C and Si react to generate SiC, and free Si with the volume fraction of 5-30% is usually present. However, for the sintering of high-purity SiC, more metal impurities are introduced in the liquid phase sintering, 5% or more of free Si exists in the reaction sintering, the purity of the SiC ceramic material cannot be guaranteed, the hot-pressing sintering temperature is greater than 1750 ℃, the required pressure is unequal, the requirements on equipment are high generally, the preparation conditions are harsh, and the industrial production cost is high. Therefore, the industrialized preparation of the high-purity SiC coating is comprehensively considered, normal-pressure sintering is preferably selected, the sintering process does not need pressurization, the process is relatively simple, the application range is wide, and the cost can be effectively saved.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating, which aims at the application limitations that the purity of the high-purity SiC ceramic coating is not easy to control, the sintering temperature is high, the preparation process is complex, and the production cost is high.

Technical scheme

A low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating capable of being massively produced is characterized by comprising the following steps:

step 1, preparing high-purity SiC slurry: dissolving high-purity SiC powder with the purity of more than or equal to 99% in ethanol and butanone, adding triethyl phosphate with the mass fraction of 2%, transferring the mixture to a ball milling tank, carrying out ball milling for 8-12 hours by using agate balls, continuously adding 3% by mass of polyvinyl butyral, 3% by mass of glycerol and dioctyl phthalate with the mixing ratio of 1:1, 5% by mass of high-purity Si powder and 2% by mass of boron carbide powder, and carrying out ball milling for 8-12 hours to form high-purity SiC slurry;

step 2, brushing: brushing the high-purity SiC slurry on the surface of the matrix, and drying at room temperature to form a precoating layer;

and 3, low-temperature pressureless sintering: and sintering the obtained precoat in an inert atmosphere at the heating rate of 2.5 ℃/min and the sintering temperature of 1750-1800 ℃, and naturally cooling to finish the low-temperature normal-pressure sintering of the high-purity SiC ceramic coating after preserving the heat for 2-3 hours.

The mixing ratio of the ethanol to the butanone is 1: 1.

The granularity of the high-purity SiC powder is 3-5 mu m and 500 nm.

Advantageous effects

The invention provides a low-temperature normal-pressure sintering preparation method of a high-purity SiC ceramic coating capable of being massively produced, and aims to effectively control the purity of the SiC coating, reduce the sintering temperature of the SiC ceramic coating under the condition of normal-pressure sintering, prepare the high-purity SiC coating, simplify the process and effectively reduce the production cost. The idea of the invention is to control the purity and sintering temperature of the SiC coating by regulating and controlling the formula of the high-purity SiC slurry, and to realize normal-pressure low-temperature sintering and batch preparation of the high-purity SiC ceramic coating without introducing any other metal impurities and the like in the processes from preparation and brush coating of the slurry to sintering.

The invention has the following beneficial effects:

(1) compared with other common preparation methods of SiC coatings, the method controls the purity of the SiC coating by regulating and controlling the formula of the high-purity SiC slurry, the slurry takes high-purity SiC powder with the purity of more than or equal to 99% as a raw material, all solvents are organic solvents and are volatile, other metal impurities and the like are not introduced, the inert atmosphere is used for protecting the processes from brush coating to sintering, and the controllability of the purity of the SiC coating is effectively realized.

(2) The coating is sintered at 1750-1800 ℃ by adding high-purity Si powder and boron carbide powder in a certain proportion into a high-purity SiC slurry formula.

(3) The high-purity SiC coating prepared by the brushing and normal-pressure sintering method is well combined with a substrate, has no obvious peeling and cracks, has the layer thickness of about 100 mu m, and compared with a magnetron sputtering method and a chemical vapor deposition method, the method can flexibly control the thickness of the high-purity SiC coating, is simple and convenient to operate, and is detailed in Table 1.

(4) The cost of slurry brushing per square meter is low, only 2-3 days are needed from slurry preparation to sintering, the operation of the technological process is simple, the consumed time is short, compared with a sputtering method and a deposition method, the method greatly reduces the equipment and preparation cost, and the mass production of high-purity SiC coatings can be realized, which is detailed in Table 1.

(5) The preparation method of the high-purity SiC coating used by the invention is suitable for the matrix and the complex component which need to have the protection performances of high temperature resistance, oxidation resistance, corrosion resistance and the like, and has wide application range compared with a magnetron sputtering method, and the details are shown in Table 1.

Drawings

FIG. 1 is a diagram of a low-temperature normal-pressure sintering preparation method of a high-purity SiC coating layer capable of being produced in mass.

FIG. 2 is a view showing high purity SiC coatings of examples 1, 2 and 3 of the present invention.

(a) High purity SiC coating in example 1; (b) high purity SiC coating in example 2; (c) high purity SiC coating in example 3

FIG. 3 is a Scanning Electron Microscope (SEM) image of high purity SiC coatings of examples 1, 2 and 3 of the present invention.

(a) High purity SiC coating in example 1; (b) high purity SiC coating in example 2; (c) high purity SiC coating in example 3

FIG. 4 is an X-ray diffraction (XRD) pattern of high purity SiC coatings of examples 1, 2 and 3 of the present invention.

(a) High purity SiC coating in example 1; (b) high purity SiC coating in example 2; (c) high purity SiC coating in example 3

FIG. 5 shows a high purity SiC coating prepared by brush coating and low temperature and atmospheric pressure sintering on a practical member.

Detailed Description

The invention will now be further described with reference to the following examples and drawings: