CN107699928A - The preparation method of black rhenium coating - Google Patents

Abstract

The invention discloses a method for preparing a black rhenium coating, which comprises the following steps: S1, molten salt chlorination: under the protection of an inert gas, after heating CsCl to a molten state, adding K ₂ ReCl ₆ to obtain K ₂ ReCl ₆ molten salt, feed chlorine gas into the molten salt containing K ₂ ReCl ₆ for chlorination, and obtain the chlorinated molten salt after cooling; S2, electroplating: heating step S1 obtained chlorinated When the molten salt is in a molten state, immerse the substrate of the plated piece in the chlorinated molten salt in the molten state, use the chlorinated molten salt in the molten state as the plating solution, use the substrate of the plated piece as the cathode, and use the inert electrode as the anode, and energize After electroplating, a black rhenium coating is obtained on the substrate of the plated piece. The preparation method of the invention has low cost and fast deposition speed, and the prepared black rhenium coating has good uniformity.

Description

Preparation method of black rhenium coating

technical field

The invention belongs to the technical field of molten salt electrochemistry and surface coating, and relates to a method for preparing a black rhenium coating, in particular to a method for preparing a high emissivity black rhenium coating by molten salt electroplating.

Background technique

Rhenium (Rhenium) is a rare refractory metal with high melting point (3180°C), high modulus, excellent high-temperature mechanical properties and thermal shock resistance, these properties make rhenium especially suitable for working at ultra-high temperature and strong thermal shock environment. In addition, metal rhenium also has very good wear resistance and corrosion resistance. The wear resistance of rhenium is second only to metal osmium (Os), and it can maintain relatively good chemical inertness to most gases except oxygen. At present, rhenium is mainly used in high-temperature fields such as high-temperature structures and energy systems (such as space missile propulsion systems), ultra-high-temperature emitters, wear-resistant erosion coatings, rockets, and satellite engine combustion chambers. Compared with the traditional rhenium with silver-white metallic luster, rhenium with parallel pointed protrusions on the microscopic scale, strong texture orientation, and black upper surface on the macroscopic scale has a higher surface emissivity, which can improve the radiation transfer energy of the material to the outside world. The rate shows better performance in the ultra-high temperature service environment. In radiation-cooled rocket engines, black rhenium can be used as the outer wall material of the engine to reduce the temperature of the engine, thereby improving the performance and working life of the engine. In addition, black rhenium is also a key material for heat exchange in solar thermal propulsion systems.

Because rhenium has a high melting point and electron emission performance, it is also widely used in the production of heating elements, electrical plugs, thermocouples, special metal wires and components in electron tubes. High temperature emitter. The electron emission performance of the material is closely related to its microstructure, and the black rhenium whose surface grows in parallel pointed shape has better electron emission performance.

There are very few research reports on black rhenium coating at home and abroad. At present, only the black rhenium coating prepared by Ultramet company of the United States by CVD method has been successfully prepared and applied. However, the traditional CVD technology has a slow deposition rate and high cost, and it is difficult to ensure the uniformity of the coating thickness at each position of the component when preparing components with complex shapes.

Therefore, providing a method for preparing a black rhenium coating with low cost, fast deposition rate and good uniformity is a technical problem that is of great concern to those skilled in the art.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a black rhenium coating with low cost, fast deposition speed and good uniformity.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A preparation method for black rhenium coating, comprising the following steps:

S1. Molten salt chlorination: under the protection of an inert gas, heat CsCl to a molten state, then add K ₂ ReCl ₆ to obtain a molten salt containing K ₂ ReCl ₆ , and introduce chlorine gas into the molten salt containing K ₂ ReCl ₆ Chlorination treatment is carried out to obtain chlorinated molten salt after cooling;

S2, electroplating: under the protection of an inert gas, heat the chlorinated molten salt obtained in step S1 to a molten state, immerse the plated piece substrate in the molten chlorinated molten salt, and use the molten chlorinated molten salt as In the plating solution, the substrate of the plated part is used as the cathode, and the inert electrode is used as the anode. Electroplating is carried out after electrification, and a black rhenium coating is obtained on the substrate of the plated part.

In the method for preparing the above-mentioned black rhenium coating, preferably, in the step S1, the heating temperature is 700°C-750°C, and the concentration of rhenium ions in the molten salt containing K ₂ ReCl ₆ is 1 wt.%- 7wt.%, the time of the chlorination treatment is 30min～60min.

In the method for preparing the above-mentioned black rhenium coating, preferably, in the step S2, the electroplating temperature is 700°C-850°C, and the cathode current density is 50mA/cm ² -100mA/cm ² .

In the method for preparing the above-mentioned black rhenium coating, preferably, in the step S2, the inert electrode is a pictograph anode matching the substrate of the plating piece, and the cathode keeps rotating during the electroplating process.

In the preparation method of the above-mentioned black rhenium coating, preferably, the substrate of the plated part includes rhenium, tungsten, iridium or graphite.

In the method for preparing the above-mentioned black rhenium coating, preferably, in the step S2, before energizing, the substrate of the plated piece is immersed in molten chlorinated molten salt for 5 minutes to 15 minutes and then electroplated.

The preparation method of the above-mentioned black rhenium coating, preferably, before the step S2, also includes pre-plating the substrate, and the pre-plating treatment includes grinding, degreasing, pickling, water washing, organic solvent washing and drying One or more of the processes; after the step S2, it also includes: taking out the cathode, cooling with the furnace under the protection of argon, and then washing and drying with water.

The method for preparing the above-mentioned black rhenium coating preferably, before the step S1, further includes: drying the CsCl to remove the water of crystallization.

In the step S1, the molten salt chlorination process is carried out in a molten salt chlorination device, the molten salt chlorination device includes a quartz barrel, a quartz cup, two inlet pipes and an outlet pipe; the quartz The cup is arranged in the quartz barrel, and the top of the quartz barrel 14 is provided with a rubber stopper for sealing, and the air inlet pipe and the air outlet pipe all pass through the rubber stopper.

In the step, the electroplating process is carried out in an electroplating device, the electroplating device includes a glove box, a stainless steel cylinder, an electroplating tank and a well-type resistance furnace, and the glove box is arranged on the stainless steel cylinder and connected with the stainless steel cylinder Sealed connection, the stainless steel tube is set in the well-type resistance furnace, the electroplating tank is set in the stainless steel tube, the open end of the stainless steel tube is provided with a cover plate, and the anode is inserted on the cover plate Rod, cathode rod, air intake pipe and thermocouple, one end of the anode rod is connected with the inert anode in the electroplating tank, the other end of the anode rod is connected with the positive terminal on the glove box through a wire, the cathode rod One end is connected to a cathode through a graphite connecting rod, the other end of the cathode rod is connected to the negative terminal on the glove box through a wire, the cathode rod can move in the vertical direction, and a Exit pipe.

In the present invention, the electroplating time is selected according to the desired coating thickness.

Compared with the prior art, the present invention has the advantages of:

1. The preparation method of the black rhenium coating of the present invention adopts chlorinated molten salt containing K ₂ ReCl ₆ as an electroplating solution, wherein K ₂ ReCl ₆ is directly added in the chloride molten salt as a source of rhenium element, The operation is convenient, and the concentration of rhenium ions is easy to control. When K ₂ ReCl ₆ is directly added to CsCl molten salt, a certain amount of disproportionation reaction will occur, that is, K ₂ ReCl ₆ →Re+ReCl ₅ ↑, and the chlorination of CsCl molten salt containing K ₂ ReCl ₆ can be very To solve the above problems well, the specific functions are as follows: first, K ₂ ReCl ₆ can be dissolved more stably in a chlorine atmosphere; second, the rhenium element generated by the disproportionation reaction can be re-chlorinated into the molten salt; third, Chlorination treatment can more effectively remove residual water vapor and impurities in molten salt. Experiments have proved that the molten salt after chlorination is macroscopically cleaner and more uniform. The molten salt of the chloride system is used as the electrolyte, and the raw material cost is low. Depending on the consumption of rhenium ions, supplementing the main salt K ₂ ReCl ₆ can reuse the electrolyte. Compared with the CVD process, the conversion utilization rate of rhenium is greatly improved, and the cost is reduced.

2. The preparation method of the black rhenium coating of the present invention adopts molten salt electroplating to prepare the rhenium coating, the speed is fast, the average deposition rate can reach 50-80 μm/h, and the coating thickness is easy to control. When the cathode is rotated and the pictorial anode is used, the thickness uniformity of the rhenium coating at each part of the component is good. The current efficiency is close to 100%, the metal coating is dense and smooth, and it is well combined with the substrate. The surface emissivity of the black rhenium coating at room temperature is greater than 0.7, which is much higher than that of rhenium prepared by other methods.

3. The preparation method of the black rhenium coating of the present invention adopts the method of sealing connection between the glove box and the molten salt electroplating device, and the immersion plating and pulling operations of the plated part substrate are all completed in the glove box, which can realize the process under strict atmosphere protection conditions. molten salt plating.

Description of drawings

Fig. 1 is the process flow chart of the preparation method of the black rhenium coating of the present invention.

Fig. 2 is a schematic diagram of the molten salt chlorination device used in the embodiment of the present invention.

Fig. 3 is a schematic diagram of the electroplating device used in the embodiment of the present invention.

Fig. 4 is a macroscopic photo of the black rhenium coating prepared at 750°C in Example 1 of the present invention.

Fig. 5 is a surface microscopic view of the black rhenium coating prepared at 750°C in Example 1 of the present invention.

Fig. 6 is a fracture microscopic view of the black rhenium coating prepared at 750°C in Example 1 of the present invention.

Fig. 7 is a surface microscopic view of the black rhenium coating prepared at 850°C in Example 2 of the present invention.

Fig. 8 is a fracture microscopic view of the black rhenium coating prepared at 850°C in Example 2 of the present invention.

Fig. 9 is a comparison chart of room temperature emissivity of rhenium prepared by different methods.

illustration:

1. Glove box; 2. Stainless steel cylinder; 3. Electroplating tank; 4. Well-type resistance furnace; 5. Cathode; 6. Anode rod; 7. Graphite connecting rod; 8. Thermocouple; 9. Cathode rod; 10. Cover Plate; 11, intake pipe; 12, positive terminal; 13, negative terminal; 14, quartz barrel; 15, quartz cup; 16, rubber plug; 17, outlet pipe.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

Example 1:

A kind of preparation method of black rhenium coating, technological process as shown in Figure 1, comprises the following steps:

(1) Molten salt chlorination:

Adopted molten salt chlorination device as shown in Figure 2 in the process of preparing molten salt, this molten salt chlorination device comprises quartz barrel 14, quartz cup 15, two air inlet pipes and an outlet pipe; Quartz cup 15 is designed In the quartz barrel 14, the top of the quartz barrel 14 is provided with a rubber plug 16 for sealing, and the air inlet pipe and the air outlet pipe all run through the rubber plug 16, wherein one air inlet pipe is used to feed chlorine gas, and the other air inlet pipe is used to pass through the rubber plug 16. into argon. When molten salt was housed in the quartz cup 15, the inlet pipe of logical chlorine was inserted in the molten salt.

Weigh the CsCl, and dry it in an oven at 200°C for 24 hours to remove the water of crystallization. Put the dried CsCl into the quartz cup 3 of the molten salt chlorination device shown in Figure 2, first use argon to clean the device three times, and then heat it to 750°C under an argon protective atmosphere to fully melt to obtain CsCl molten salt. Stir the CsCl molten salt and add K ₂ ReCl ₆ to the CsCl molten salt, so that the rhenium ion concentration in the molten salt containing K ₂ ReCl ₆ is 5wt.%, pass chlorine gas into the molten salt containing K ₂ ReCl ₆ for chlorination 30 minutes, and finally cooled under the protection of argon to obtain the chlorinated molten salt.

In this embodiment, only the concentration of rhenium ions is given, and the amounts of CsCl and K ₂ ReCl ₆ may vary according to the required size of the final product.

(2) Pre-treatment of plated parts: the plated parts are made of graphite, smoothed with No. 2000 sandpaper before electroplating, and ultrasonically cleaned with acetone for 15 minutes to remove the residual graphite powder on the surface, and then fully dried in an oven at 120 ° C to obtain the substrate of graphite plated parts .

(3) Electroplating:

Adopted the electroplating device shown in Figure 3 in the electroplating process, this electroplating device comprises glove box 1, stainless steel tube 2, electroplating tank 3 and well type resistance furnace 4, and glove box 1 is located on stainless steel tube 2 and is connected with stainless steel tube 2 are sealed and connected, the stainless steel tube 2 is set in the hearth of the well-type resistance furnace 4, and the electroplating tank 3 is set at the bottom of the stainless steel tube 2. The electroplating tank 3 is specifically a graphite crucible, and the graphite crucible is also an inert anode, and is designed to be a pictorial anode matching the substrate of the plating piece. The open end of the stainless steel cylinder 2 is provided with a cover plate 10 on which an anode rod 6 , a cathode rod 9 , an air inlet pipe 11 and a thermocouple 8 are inserted. One end of the anode rod 6 is connected to the electroplating tank 3 (that is, the graphite anode), and the other end of the anode rod 6 is connected to the positive terminal 12 on the glove box 1 through a wire, and the positive terminal 12 is connected to the positive pole of the power supply. One end of the cathode rod 9 is connected to the cathode 5 (that is, the substrate of the plated part) through the graphite connecting rod 7 to prevent the cathode rod 9 from being directly connected to the cathode 5 and will be corroded in the molten salt. The other end of the cathode rod 9 is connected to the glove tube through the wire 1 is connected to the negative terminal 13, and the negative terminal 13 is connected to the positive pole of the power supply. The cathode rod 9 can move in the vertical direction, which can facilitate the dipping and pulling operations on the substrate of the plated part from the glove box. Since the glove box 1 is sealed and connected with the stainless steel cylinder 2, the dipping and pulling operations of the substrate of the plated part can be performed smoothly. Finished in the glove box, molten salt electroplating under strict atmosphere protection conditions can be realized. The wires used in this embodiment are preferably iron-chromium-aluminum wires protected by quartz tubes. The thermocouple 8 inserted on the cover plate 10 is used to measure and control the temperature of the molten salt in the electroplating tank 3 . The air inlet pipe 11 inserted on the cover plate 10 is used for passing argon gas. The side of the stainless steel cylinder 2 is also provided with an air outlet pipe 17, and the air outlet pipe 17 can be used for releasing exhaust gas.

Put the chlorinated molten salt obtained in step (1) into the graphite crucible of the electroplating device shown in Figure 3 and assemble the electrodes, vacuumize the device and clean the device three times with argon gas, and melt Heat the salt to 750°C, and after the chlorinated molten salt melts, insert the graphite plated substrate (cathode 5) obtained in step (2) into the molten salt, keep it warm for 10 minutes, and then start electroplating, the electroplating temperature is 750°C , the cathode current density is 50mA/cm ² , the electroplating tank 3 (inert anode) is protected by Ar, the electroplating time is 1 hour, and a black rhenium coating is formed on the substrate of the plated piece.

Wherein, the base of the graphite-coated part in this embodiment is a cylinder, and the contour of the inner wall of the graphite crucible is designed to be consistent with the outer contour of the base of the graphite-coated part, so as to form a simple pictorial anode.

(4) Cleaning of plated parts: Take out the cathode plated parts and cool them down to room temperature under the protection of Ar gas, ultrasonically clean the samples with water to remove residual molten salt on the surface, and dry them to obtain the plated parts coated with black rhenium coating.

Fig. 4 is the macrophotograph of the black rhenium coating prepared in this embodiment, the coating surface is smooth and black. Fig. 5 and Fig. 6 are respectively the microscopic appearance diagrams of the surface and fracture of the black rhenium coating prepared in this example. After testing, the surface of the coating is densely packed with apex-shaped grains with a particle size of less than 5 μm, and the grains are irregular. Polygonal shape, the coating thickness is about 40μm. According to the national standard GB 5210-85 "Determination of Coating Adhesion Pulling Method", the obtained black rhenium coating was pulled apart. The measured average tensile strength was 10.2MPa, and the breaking position was between the coating and the substrate. Meeting point. The surface emissivity of the black rhenium coating at room temperature is 0.73.

Example 2:

A method for preparing a black rhenium coating, the steps of which are basically the same as in Example 1, the only difference being that the electroplating temperature in step (3) is 850°C.

Fig. 7 and Fig. 8 are respectively the microscopic appearance diagrams of the surface and fracture of the black rhenium coating prepared in this embodiment. It can be seen from the figure that the coating surface is smooth and gray-black. The grain size of the coating is larger than that of Example 1, and the surface is densely packed with pointed and tower-shaped grains with a grain size less than 10 μm, and the coating thickness is about 40 μm. According to the national standard GB 5210-85 "Determination of Coating Adhesion-Pull-Off Method", the pull-off test is carried out. The average tensile strength measured is 12.2MPa, and the break-off position is the joint between the coating and the substrate. The surface emissivity of rhenium coating at room temperature is 0.7.

Comparative example:

The surface emissivity of rhenium prepared by the molten salt electroplating method (ED method) of the present invention, conventional powder metallurgy method (PM method) and conventional chemical vapor deposition method (CVD method) at room temperature is compared, as shown in Figure 9 As shown, it can be seen that the surface emissivity of black rhenium (ED rhenium) prepared by the molten salt electroplating method of the present invention is significantly higher than that of PM rhenium and CVD rhenium.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art, without departing from the spirit and technical solutions of the present invention, can use the methods and technical content disclosed above to make many possible changes and modifications to the technical solutions of the present invention, or modify them to be equivalent Variations of equivalent embodiments. Therefore, any simple modifications, equivalent replacements, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the technical solutions of the present invention, still fall within the protection scope of the technical solutions of the present invention.

Claims (10)

1. a preparation method of black rhenium coating, comprising the following steps: S1. Molten salt chlorination: under the protection of an inert gas, heat CsCl to a molten state, then add K ₂ ReCl ₆ to obtain a molten salt containing K ₂ ReCl ₆ , and introduce chlorine gas into the molten salt containing K ₂ ReCl ₆ Chlorination treatment is carried out to obtain chlorinated molten salt after cooling; S2, electroplating: under the protection of an inert gas, heat the chlorinated molten salt obtained in step S1 to a molten state, immerse the plated piece substrate in the molten chlorinated molten salt, and use the molten chlorinated molten salt as In the plating solution, the substrate of the plated part is used as the cathode, and the inert electrode is used as the anode. Electroplating is carried out after electrification, and a black rhenium coating is obtained on the substrate of the plated part. 2. The preparation method of black rhenium coating according to claim 1, characterized in that, in the step S1, the heating temperature is 700°C to 750°C, and the rhenium in the molten salt containing K ₂ ReCl ₆ The ion concentration is 1wt.%-7wt.%, and the chlorination treatment time is 30min-60min. 3. The preparation method of black rhenium coating according to claim 1, characterized in that, in the step S2, the temperature of the electroplating is 700°C-850°C, and the cathode current density is 50mA/cm ² -100mA/ cm ² . 4. The preparation method of the black rhenium coating according to claim 1, characterized in that, in the step S2, the inert electrode is a pictographic anode matched with the plating substrate, and the cathode keeps rotating during the electroplating process. 5. The preparation method of the black rhenium coating according to any one of claims 1 to 4, characterized in that, the substrate of the plated part comprises rhenium, tungsten, iridium or graphite. 6. according to the preparation method of the black rhenium coating described in any one in claim 1～4, it is characterized in that, in described step S2, before energizing, the chlorinated molten salt after immersing the plated piece substrate in molten state Keep warm for 5 minutes to 15 minutes in the middle, and then carry out electroplating. 7. The preparation method of the black rhenium coating according to any one of claims 1 to 4, characterized in that, before the step S2, it also includes carrying out pre-plating treatment on the substrate of the plated piece, and the pre-plating treatment includes grinding , degreasing, pickling, water washing, organic solvent washing and drying treatment; after the step S2, it also includes: taking out the cathode, cooling with the furnace under the protection of argon, and then washing and drying . 8 . The method for preparing the black rhenium coating according to any one of claims 1 to 4 , characterized in that, before the step S1 , further comprising: drying CsCl to remove crystal water. 9. according to the preparation method of the black rhenium coating described in any one in claim 1～4, it is characterized in that, in described step S1, the process of described molten salt chlorination is carried out in molten salt chlorination device, The molten salt chlorination device comprises a quartz barrel (14), a quartz cup (15), two inlet pipes and an outlet pipe; the quartz cup (15) is arranged in the quartz barrel (14), and the quartz barrel (14 ) is provided with a rubber plug (16) for sealing, and both the air inlet pipe and the air outlet pipe run through the rubber plug (16). 10. The preparation method of the black rhenium coating according to any one of claims 1 to 4, characterized in that, in the step S2, the electroplating process is carried out in an electroplating device, and the electroplating device includes gloves Box (1), stainless steel tube (2), electroplating tank (3) and well type resistance furnace (4), the glove box (1) is set on the stainless steel tube (2) and sealed with the stainless steel tube (2) connection, the stainless steel tube (2) is set in the well-type resistance furnace (4), the electroplating tank (3) is set in the stainless steel tube (2), and the open end of the stainless steel tube (2) A cover plate (10) is provided, and an anode rod (6), a cathode rod (9), an air inlet pipe (11) and a thermocouple (8) are inserted on the cover plate (10), and the anode rod (6) One end of the anode rod (6) is connected to the inert anode in the electroplating tank (3), the other end of the anode rod (6) is connected to the positive terminal on the glove box (1) through a wire, and one end of the cathode rod (9) is connected through a The graphite connecting rod (7) is connected to a cathode (5), and the other end of the cathode rod (9) is connected to the negative terminal on the glove box (1) through a wire, and the cathode rod (9) can be vertically Direction movement, the stainless steel cylinder (2) is also inserted with an outlet pipe (17) on the side.