CN1239739C - Method for preparing composite coat layer of diamond being plated slimline with low roughness in inside surface - Google Patents

Abstract

Preparation method of diamond composite coating slender tube with low inner surface roughness. The method uses electron-enhanced hot-wire chemical vapor deposition (CVD) method to prepare diamond composite coating on the tungsten rod substrate, and removes the tungsten rod substrate by etching to obtain a self-supporting diamond thin tube, and adopts a method slightly larger than the self-supporting diamond thin tube. The steel pipe or aluminum tube is used as the shell of the slender tube, which is set outside the self-supporting diamond tube, and the modified epoxy resin binder is filled between the self-supporting diamond tube and the shell, thereby forming an inner surface composed of a low Slender tubes composed of roughness diamond composite coatings. This method can not only obtain a wear-resistant diamond coating with high adhesion strength on the inner surface of the slender tube, but also effectively reduce the roughness of the inner surface of the slender tube through process control, thereby greatly improving its friction performance and improving the working life of the slender tube. Productivity and processing quality. The method is simple in operation, convenient in application and bright in industrialization prospect, thus having remarkable economic benefits.

Description

Preparation method of diamond composite coated slender tube with low inner surface roughness

Technical field

The invention relates to a method for preparing a diamond-coated elongated tube, in particular to a method for preparing an elongated tube with a low-roughness diamond composite coating on the inner surface by using an electron-enhanced hot-wire chemical vapor deposition (CVD, Chemical Vapor Deposition) method The invention belongs to the technical field of diamond coating preparation for wear-resistant devices.

Background technique

Diamond has a series of excellent properties, it has very high hardness, high modulus of elasticity, high thermal conductivity, low coefficient of friction, low coefficient of thermal expansion and chemical stability as well as excellent resistance to acid, alkali and The excellent performance of various corrosive gas erosion has been widely used in the preparation of cutting tools and wear-resistant devices. As a wear-resistant material for outer surface coatings, diamond thin films have been successfully applied to the protective layer of magnetic disks and optical discs, the surface coating protection of precision punching dies, and the coating of wearable mechanical components on automobile engines. In fact, as the most ideal tool and wear-resistant material, diamond film is also reflected in its application in many occasions where the inner surface requires wear resistance and lubrication, such as wire drawing dies, slender tubes, nozzles, etc. In the actual production process, the above-mentioned tools will be seriously affected due to serious wear and tear, which will seriously affect the production efficiency and processing quality. Polycrystalline diamond and thick-film diamond have begun to be used in the preparation of wire drawing dies and nozzles with an aperture of less than 2 mm. Polycrystalline diamond slender tubes are also commercially available, and the problem of wear and tear has been solved. However, the investment in manufacturing equipment for the product is large, making Products are very expensive. For the preparation of large-diameter wire drawing dies and nozzles, polycrystalline diamond and thick-film diamond materials are rarely used. The increasingly mature hot wire chemical vapor deposition (CVD) diamond coating technology brings hope to the preparation of large-aperture inner surface wear-resistant parts. It has the advantages of large area, random shape and low cost. The key to the industrial preparation of grinding parts. As wearable parts such as wire drawing dies, sliding bearings, nozzles and elongated nozzles, if diamond films are used as wear-resistant materials, the failure of their functions depends mainly on the wear degree of the inner surface diamond films, so diamond films The friction and wear characteristics of the material become the primary concern. Relevant studies have shown that the friction and wear characteristics of the diamond film are closely related to the roughness of the coating surface, and it will be a difficult problem in the coating process to obtain a low-roughness diamond film on the inner surface of the slender tube. At present, there is no success in actual production. Examples of applications.

Contents of the invention

In order to overcome the shortage that the inner surface of the existing slender tube is seriously affected by severe wear and tear during work, the invention provides an electron-enhanced hot wire chemical vapor deposition (CVD) ) method to prepare the slender tube with low roughness diamond composite coating on the inner surface. This method can not only obtain a wear-resistant diamond coating with high adhesion strength on the inner surface of the slender tube, but also effectively reduce the internal The roughness of the diamond coating on the surface greatly improves its friction performance, and improves the working life, production efficiency and processing quality of the slender tube.

The technical solution adopted by the present invention to solve the technical problem is: the preparation method adopts the electron-enhanced hot wire chemical vapor deposition method to first carry out fine-grain diamond coating on the tungsten rod substrate after the surface polishing treatment, at this time, the tungsten rod substrate It is not necessary to take it out of the electron-enhanced hot wire chemical vapor deposition reaction chamber, and then increase the reaction gas pressure, reduce the volume ratio of acetone/hydrogen and remove the inert gas argon to prepare a composite coating of coarse-grained diamond coating in situ, After the tungsten rod matrix is removed by corrosion, a self-supporting diamond tube with a smooth inner surface is obtained. A steel pipe or aluminum tube slightly larger than the self-supporting diamond tube is used as the shell of the slender tube, which is set outside the self-supporting diamond tube, and A modified epoxy resin binder is filled between the self-supporting diamond tubule and the outer shell, thereby forming an elongated tube with an inner surface composed of a low-roughness diamond composite coating.

Firstly, according to the inner diameter of the slender tube required, a tungsten rod material with an appropriate diameter that is easy to grow diamond is selected as the substrate, and the surface of the tungsten rod substrate surface is made as smooth as possible through surface polishing, and then the electron-enhanced hot wire CVD method is used to apply stage-by-stage deposition The diamond composite coating is prepared on the tungsten rod substrate. In the early stage of diamond deposition, the nucleation rate of diamond is mainly increased, and the secondary formation is promoted by increasing the concentration of carbon source gas, reducing the temperature of the substrate, and reducing the pressure of the deposition chamber. The number of nuclei increases, the grains are refined, and nano-spherical grains with <100> crystal orientation as the main direction, poor crystal shape, and fine grains are formed. In the middle and late stages of diamond deposition, the concentration of carbon source gas should be reduced and the substrate temperature should be increased. On the grown diamond coating, a layer of <111> crystal orientation, thick grains and good crystallinity diamond polycrystalline film is deposited and grown in situ. Through the above technological measures, a diamond composite coating with a thickness of about 10-50 μm can be deposited on the tungsten rod substrate. Then the tungsten rod substrate is removed by etching to prepare a self-supporting diamond thin tube with a certain wall thickness. Before the deposition, the tungsten rod substrate is surface polished and special process parameters are used to refine the diamond grains at the initial stage of diamond coating deposition. , so that the inner surface of the self-supporting diamond capillary coating prepared after corrosion is very smooth. Then use the steel pipe or aluminum tube that meets the diameter size requirements as the outer shell of the slender tube, use the prepared self-supporting diamond thin tube as the inner shell, and fill the space between the self-supporting diamond thin tube and the outer shell with modified epoxy resin to withstand And the external load acting on the inner surface of the diamond composite coating is released to avoid the cracking and failure of the diamond coating due to stress concentration, thereby forming a slender tube whose inner surface is composed of a low-roughness diamond composite coating.

The beneficial effect of the present invention is that the method can not only obtain a wear-resistant diamond coating with high adhesion strength on the working surface of the inner layer of the slender tube, but also effectively reduce the inner surface roughness of the self-supporting diamond thin tube through process control, thereby greatly improving Its friction performance improves the working life, production efficiency and processing quality of the slender tube. The method is simple in operation, convenient in application and bright in industrialization prospect, thus having remarkable economic benefits.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with the preparation example of an elongated tube with a low-roughness diamond composite coating on the inner surface to obtain a fine-grained and low-roughness diamond film on the inner surface.

Step 1: First, according to the inner diameter of the slender tube required, select a tungsten rod material with a corresponding diameter that is easy to grow diamond as the substrate, and make the surface of the tungsten rod substrate as smooth as possible through surface polishing.

The second step: place the polished tungsten rod substrate in the electron-enhanced CVD reaction chamber, and apply the electron-enhanced hot-wire CVD method for fine-grain diamond coating. The hot filament adopts ф0.6 mm tantalum wire, which is straightened by a high temperature resistant spring. After the reaction chamber is evacuated, the reaction gas (hydrogen and acetone) is introduced. After adjusting the pressure of the reaction chamber, CVD deposits a fine-grained diamond coating. Coating process parameters are: pressure 0.5-2KPa, total reaction gas flow rate 200-400 ml/min, acetone/hydrogen volume ratio (carbon source concentration) 2%-6%, filament temperature 2000°C, bias current 1A, The inert gas argon (Ar) is added, and the volume ratio of argon/hydrogen (Ar/H ₂ ) is 0.5-1.5. Compared with the traditional CVD diamond coating process, due to the reduction of the reaction gas pressure, the increase of the carbon source concentration and the addition of inert gases, the speed of the secondary nucleation of diamond can be greatly increased, and thus the deposition of fine-grained nano Diamond coating, the crystal particle size is about 50-100 nanometers, the coating surface is relatively smooth, the friction coefficient is small, and the hardness is also reduced. After 2 hours, a fine-grained diamond coating with a thickness of about 5 microns was obtained.

The third step: Coarse-grain diamond coating. After the fine-grained diamond coating reached 5 microns, the in-situ deposition of the coarse-grained diamond coating was started. At this time, the tungsten rod substrate does not need to be taken out from the electron-enhanced hot wire CVD reaction chamber. It only needs to change the process conditions, that is, increase the reaction gas pressure, reduce the carbon source concentration and remove the inert gas argon. The reaction gas pressure can be increased to 4-10KPa, the carbon source concentration can be reduced to 1-3%, the argon gas can be removed, and the temperature of the filament can be increased appropriately to 2200°C. By changing the above process parameters, the concentration of hydrogen ions in the reaction atmosphere can be greatly increased, and the etching of graphite and amorphous carbon during the diamond growth process can be enhanced, thereby promoting the diamond grains to change from <100> with poor crystal shape and fine grain The crystal direction changes from nano-spherical grains to coarse grains and good crystallinity <111> crystals to triangular (mixed with square) coarse grains. After 4 hours of deposition, a layer of coarse-grained diamond coating with a thickness of about 15 microns is thus prepared. The surface of the coating is very rough, the coefficient of friction is large, and the hardness is high, which is conducive to improving the quality of the diamond coating and can be more Bonds well with epoxy adhesives.

Step 4: Take the tungsten rod material deposited with the diamond composite coating out of the electron-enhanced hot wire CVD reaction chamber, and put it into a container containing the corrosive liquid to remove the tungsten rod material matrix, thereby preparing a self-supporting diamond fine Tube. The preparation scheme of the corrosive solution is as follows: the volume ratio of hydrochloric acid with a specific gravity of 1.19 and hydrogen peroxide with a concentration of 30% is 1:1.

Step 5: After taking out the self-supporting diamond thin tube from the container containing the corrosive liquid, in order to increase the bonding force between the diamond coating and the epoxy resin, the following surface treatment should be carried out on the prepared self-supporting diamond thin tube: (1) Oxygen plasma surface treatment to remove the amorphous carbon on the outer surface of the coating and generate carbon-oxygen (C=O) bonds in local areas to make the coating wet with epoxy resin; (2) The outer surface of the layer is sputtered with titanium (Ti) or chromium (Cr) metal which can form carbides with diamond, and coated with Ti-containing monoalkoxy titanate coupling agent.

Step 6: Use a steel pipe or aluminum tube slightly larger than the self-supporting diamond thin tube as the shell of the elongated tube, and put it on the prepared self-supporting diamond thin tube, and change the distance between the self-supporting diamond thin tube and the shell. Glycidyl ether bisphenol-propane type epoxy resin binder is filled to bear and release the external load acting on the inner surface of the diamond composite coating, avoiding the cracking and failure of the diamond coating due to stress concentration, thus forming the inner surface An elongated tube consisting of a low-roughness diamond composite coating. In order to reduce the thermal expansion coefficient of the epoxy resin binder and prevent the stress cracking of the coating due to the large difference in the expansion coefficient, it is necessary to add silicon dioxide (SiO ₂ ) micropowder and styrene toughener to the epoxy resin formulation. The resin binder is modified.

Claims (2)

1. internal surface low roughness diamond composite coating elongated tubular preparation method, it is characterized in that the tungsten bar material matrix that this preparation method adopts electronics to strengthen after hot filament CVD is handled surface finish carries out the fine-particle diamond coating earlier, tungsten bar material matrix needn't strengthen the hot filament chemical vapor deposition reactor chamber from electronics and took out this moment, improve reaction gas pressure then, reduce the volume ratio of acetone/hydrogen and remove the compound coating preparation that the rare gas element argon gas carries out the coarse grain diamond coatings in position again, by obtaining the slick self-supporting diamond tubule of internal surface behind the erosion removal tungsten bar material matrix, employing is than the bigger steel pipe of self-supporting diamond tubule or the aluminum pipe shell as elongated tubular, be enclosed within outside the self-supporting diamond tubule, and between self-supporting diamond tubule and shell, fill by the epoxy adhesive of modification, form the elongated tubular that internal surface is made up of the low roughness diamond composite coating thus.

2. internal surface low roughness diamond composite coating elongated tubular preparation method according to claim 1, its feature is that also this preparation method comprises:

[1] the tungsten bar material of easy growing diamond of at first selecting respective diameters according to needed elongated tubular internal diameter is as matrix, handles making that tungsten bar material matrix surface is smooth as far as possible by surface finish;

[2] will place electronics to strengthen chemical vapor deposition reaction chamber through the tungsten bar material matrix after the surface finish processing, hot filament adopts the tantalum wire of 0.6 millimeter of ф, stretching with high temperature resistant spring, reaction chamber vacuumizes the back and feeds hydrogen and acetone, begin chemical vapour deposition fine-particle diamond coating after adjusting chamber pressure, the coating process parameter is: pressure 0.5-2KPa, reactant gases total flux 200-400 ml/min, the volume ratio of acetone/hydrogen is 2%-6%, filament temperature is 2000 ℃, bias current 1A adds rare gas element Ar, Ar/H ₂Volume ratio is 0.5-1.5, after 2 hours, obtains thick 5 microns fine-particle diamond coating;

[3] after the fine-particle diamond coating reaches 5 microns, beginning in-situ deposition coarse grain diamond coatings, improve reaction gas pressure to 4-10KPa, the volume ratio that reduces acetone/hydrogen is to 1-3%, remove argon gas, improve simultaneously suitably filament temperature to 2200 ℃, through after 4 hours depositions, prepare the coarse grain diamond coatings of 15 microns of bed thickness again;

[4] the tungsten bar material that will deposit diamond composite coating takes out from electronics enhancing hot filament chemical vapor deposition reactor chamber, put in the container that fills corrosive fluid to remove tungsten bar material matrix, thereby prepare the self-supporting diamond tubule, the corrosive fluid preparation program is: proportion is that 1.19 hydrochloric acid and concentration are that the volume proportion of 30% hydrogen peroxide is 1: 1;

[5] from the container that fills corrosive fluid, take out the self-supporting diamond tubule after, for increasing the bonding force between diamond coatings and Resins, epoxy, also to carry out following surface treatment: (1) oxygen plasma surface treatment to the self-supporting diamond tubule for preparing, to remove the decolorizing carbon of coating outside surface, and, make coating mutually moistening with Resins, epoxy at regional area generation C=O key; (2) can generate the Ti or the Cr metal of carbide with diamond in the sputter of coating outside surface, and apply the monoalkoxy type titanate coupling agent that contains Ti;

[6] again will be than the bigger steel pipe of self-supporting diamond tubule or aluminum pipe shell as elongated tubular, be enclosed within outside the self-supporting diamond tubule, between self-supporting diamond tubule and shell, fill, form the elongated tubular that internal surface is made up of the low roughness diamond composite coating thus by the Racemic glycidol ethers propane type epoxy resin of di phenolic group binding agent of modification.