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Rhenium and rhenium alloys and manufacturing technology application status

Date:2015-04-17 17:55

Rhenium is a rare and refractory metals, high melting point, high strength and good ductility and excellent mechanical stability, its melting point after tungsten, up to 3180 ℃, rhenium no critical brittle transition temperature, high temperature and thermal shock conditions are very good creep resistance, thermal shock suitable for ultra-high temperature and intense work environment, their room temperature tensile strength than the anti-1172 MPa, 2200 ℃ while still maintaining at 48 MPa or more, far more than other metals. Rhenium at high temperature has a very good thermal shock resistance, high temperature 2200 ℃, the rhenium-made engine nozzle can withstand 100 000 thermal fatigue cycles without failure. Moreover, rhenium also very good wear resistance, corrosion resistance, abrasion resistance force behind its metal osmium, except for most of the oxygen gas to maintain good chemically inert, will not be hot hydrogen corrosion, to hydrogen permeability is low. Because of a series of excellent properties, rhenium and its alloys are widely used in petrochemical, electronics and aerospace industries, has become one of the most important new materials, modern high-tech fields.

Application Status rhenium and rhenium alloys
1.1 petrochemical industry
Rhenium maximum use is made of the petrochemical industry catalyst (approximately 60% of all of the above rhenium), due to the electronic structure of rhenium in its unsaturated 4d layer 5 is easy to emit electrons, and layer two 6s electrons and ease of participation covalent bond formed by the action, coupled with a larger lattice parameters and other characteristics, the rhenium compound and having excellent catalytic activity, the catalyst system producing high octane gasoline using earlier platinum reforming apparatus, i.e., a Pt- Re, the rhenium consumption accounted for more than 70% of world consumption of rhenium at the time. Since the US Global petroleum products developed by continuous catalytic regeneration (CCR) platinum reconnection process, Pt-Rc are no longer used as the catalyst in this process, the application amount of rhenium declined. However, recent reports that for platinum CCR process. Tin catalyst effectiveness is not ideal, Rt. Re catalyst system has been reapplied. In addition, rhenium is used to produce unleaded gasoline and car exhaust purification catalyst; with NH. Re04 / C catalyst for cyclohexane dehydrogenation and dehydrogenation of ethanol; Re207 is to make the S02 into S03
HN02 and make a good catalyst for the conversion of HN03. In addition, metal and alloy plated rhenium-rhenium alloy and composite materials, but also for the petrochemical industry corrosion, corrosion resistance, particularly to prevent corrosion of hydrochloric acid. Have been developed on the copper, brass and nickel electroless plating method rhenium and rhenium tungsten halides decompose on the rhenium vapor deposition method.
1.2 Aerospace
Rhenium is one of the hardest melting metal. Rhenium alloy forming member and is mainly used for aerospace components, a variety of solid propulsion thermal elements, anti-oxidation coating. The rhenium and other metals can produce a series of high temperature, corrosion-resistant, wear-resistant alloy, such as a W was Re25 station nuclear reactor materials; Re-Pt is used as nuclear reactor structural materials, high temperature resistant 1000 ℃ hot body download corrosion; Re. Mo alloy to 3000 ℃ still have high mechanical strength, it can be used to manufacture missiles and supersonic aircraft high temperature
Strength components. From the 1980s, NASA began to study under Ultramet company to do rhenium metal substrate, high temperature anti-oxidation coating is made of iridium metal liquid rocket engine combustion chamber, and has successfully prepared and used in satellite attitude control engine . Ultramet also by CVD deposition of rhenium metal coating on the graphite substrate used to make rocket engine jet vane. Experiments show that the rhenium metal and graphite can be a good or C. C substrate binding, compared with other hard metal carbides, rhenium and graphite or C. C is combined with plastic, good thermal compatibility, so its melting point is higher than the carbide or other hard metal, and in the presence of gas, showing a chemically inert. Since rhenium metal corrosion and hydrogen also has a low heat of hydrogen permeability are used to make rocket solar heat exchanger member, through which the heat exchanger member, the solar radiation heat is transmitted to the hydrogen gas, and hydrogen gas is sucked rhenium tube where the this thrust, the maximum operating temperature up to 2500 ℃. In recent years, the amount of rhenium in superalloys aspect has exceeded the amount of catalyst in terms of its superalloys has become their most important applications.
1.3 Metallurgical Industry
Rhenium alloy can be used as additives in the metallurgical industry. Alloy addition of rhenium can greatly improve the properties of the alloy, especially as tungsten or molybdenum additives may increase tungsten, strength molybdenum alloy overcome these metal embrittlement tendency after recrystallization in improved formability and weldability of metal, so that tungsten and molybdenum alloys have better robustness and stability. Molybdenum-rhenium alloy tensile strength is greater than 2 times more than pure molybdenum, delamination, processing performance is better than that of pure molybdenum. Molybdenum-rhenium alloy is non-magnetic, metal and glass can be used to seal, for high temperature thermocouple protection kits and high temperature furnace components. Adding tungsten rhenium alloy can improve their high temperature performance and high-temperature ductility, W-Re alloy harder than pure tungsten, the tensile strength of up to 3260 MPa2, wear several times larger than that of pure tungsten, easy to weld, and the processing temperature range wide. Addition of rhenium and platinum alloys rhodium is possible to improve the wear resistance without lowering its corrosion resistance, these alloys are also used as a thermocouple material.
1.4 electronic materials and high-temperature materials
Rhenium, tungsten-rhenium alloys have good corrosion resistance, arc erosion resistance, "water cycle" aggressive and high hardness, high thermal electron emission properties, is a good electrical contact materials, even with the partial oxidation nor affect its conductive properties, especially for high temperature, high humidity environment. Rhenium temperature resistance, is widely elements, thermocouples, special wires and tubes in the elements for heating. In this area, rhenium most prominent application is to create ultra-high temperature emitter. Tungsten Co., Ltd., Tokyo, Japan
Work on tungsten single crystal orientation of the substrate coated with the functional material containing rhenium group niobium, tantalum, molybdenum alloys and composites emission system as a high temperature electrode base material, the hot electron discharge effect increased by 20%, but also greatly enhance the current density improved thermoelectric emission performance. W-Re and W-Th. Re alloy is used as tube elements, can improve the strength of the tube member, made of heating wire heater, even after the recrystallization and carburization can be avoided from being damaged. Since rhenium vapor pressure is small, when used as a cathode made of nickel matrix it instead of nickel. Rhenium alloy or coating material with tungsten, molybdenum, or platinum group consisting of, because of its high melting point, high electrical resistance and good environmental stability and is widely used in the electronics industry. Mixed with 3% --- 20% Re H4Re04 tungsten or tungsten wire coating, not as brittle as tungsten, but also improve their elongation and resistance, with high shock and vibration performance, so in a vacuum electronics or filament technology and vibration-prone places in demonstrating its important purposes, such as X-ray target, flash, sonographer, high voltage measuring vacuum parts, aircraft bulb tungsten-rhenium wire, etc. p "cited.
The method of manufacturing the device rhenium
Rhenium has a series of extremely excellent performance in defense and aerospace and other fields have broad prospects should, however, be prepared rhenium processing is more difficult. Currently, there are devices producing rhenium electrochemical deposition, powder metallurgy, chemical vapor deposition and physical vapor deposition of four kinds of methods.
2.1 electrochemical deposition
Generally, the refractory metal because of its high melting point, so preparation is relatively difficult, but compared with other refractory metals, certain salts of rhenium metal has good solubility, it is possible to use electrochemical rhenium deposition Method. Electrochemical methods, can be obtained rhenium or rhenium coating film at a lower temperature, at present this technology has been widely used in the preparation of rhenium metal surface coating. Rhenium chemistry electrochemical deposition of the equation can be expressed as follows:
Re04 '+ 4H20 + 7e-} ReO + 80H. (1)
Re04 "+ 4H ++ 7 e_ ÷ ReO + 4H2 (2)
Wherein the reaction equation rhenium deposited separately under alkaline conditions and acid solution electrochemical formula (1) and (2). As can be seen from the formula (1) and (2), Re04 reduced to metallic rhenium, it must accept the electrons 7, but in this case a strong oxidizing atmosphere, the deposited rhenium most likely because of the oxidation of making it difficult to improve the purity. Further, rhenium restore requires a relatively high potential difference, so that in the case of the reduced Re04, may be accompanied by other reactions occur, affecting the efficiency of deposition of rhenium and surface quality and purity. Finally, the deposition process Re04- enrichment will be a strong rejection of the cathode region of the cathode itself. Despite the optimization of reaction parameters, such as the appropriate solution concentration and deposition voltage can be obtained relatively quickly rhenium coating at a lower temperature, but a series of disadvantages inherent in electrochemical, deposition loose structure of the product, poor uniformity, dimensional accuracy not prepared for higher member such as rhenium rhenium pipes, wire restricted
2.2 powder metallurgy
Powder metallurgy method is to prepare a refractory metal of more effective methods are now widely used in the manufacture of metal rhenium products. Cold isostatic pressing powder metallurgy technology, parts manufacturing time and material loss reduction was significantly reduced, and because the amount of powder can be filled by controlling the thickness control components, precision parts NT also to a large extent improved. Powder Metallurgy part body, it is heated to 1500 ℃ calcined, then, then it was heated to 2200 ℃ final hot isostatic pressing after sintering, the dimensional accuracy is further improved. After hot isostatic pressing of products for cutting, roughing, finishing and polishing process can be obtained very high dimensional accuracy of the parts, at present, the United States Rhenium Alloys application of this technology has already prepared a wall thickness of 4 mm thin-walled parts. Application of powder metallurgy method, although some metals rhenium component can be prepared, but for more complex shapes, small diameter, there are considerable difficulties in a relatively thin wall thickness of structural parts, powder metallurgy. In these respects, the physical
Vapor deposition and chemical vapor deposition method are a competitive advantage [17,1 cited.
2.3 an electron beam physical vapor deposition
Electron beam. Physical vapor deposition (EB.PVD) is a physical vapor deposition method, each of the products and rhenium net effective rhenium film forming tooling. EB. PVD technology is a vacuum in the high-energy electron beams to focus on the source material, so that the source material is volatile molecules condensed material preparation technology on the substrate. Forming a coating in two steps: nucleation and growth. Its deposition rate and the coating thickness depends on the volatilization rate, deposition time, the chamber pressure, and the electron beam from the volatile power source and the substrate. The advantage of this technology is the flexibility to control the composition and organization of the coating, in the case of using a plurality of different sources of volatile components can be obtained a variety of different components of the coating, the deposition rate and adjusting the deposition thickness can be obtained different organizations. Binding matrix method disappear technology, prepared by EB-PVD metal rhenium thin-walled structures, in the process, before depositing relatively thick metal rhenium coating on a molybdenum substrate. Layer, and finally removing the matrix using electrochemical methods, can be obtained rhenium metal member 21 fl Pi.
2.4 chemical vapor deposition (CVD)
Preparation of rhenium pipes commonly used chemical vapor deposition (CVD). Chemical vapor deposition is the use of a chemical reaction, precipitated solid phase material is deposited in the working surface of the coating film formed of a material from the gas phase technology. By chemical vapor deposition, a thickness up to several millimeters can be obtained rhenium metal thin film on the substrate surface. And the preparation of very high purity metal rhenium, 99.99% - 99.999%; a density of up to 99.5% of the theoretical value. Since the chemical vapor deposition own characteristics,
Application of this method, for the preparation of difficult to machine metals have advantages from the raw material can be obtained once the required size of the pipe to avoid cumbersome manufacturing processes. Chemical vapor deposition rhenium tube defects and voids very little against the mandrel (Mo) side there is a small equiaxed and columnar grain is coarse, depositions of columnar crystals can not form a continuous, achieve the ideal structure form. Meanwhile, powder metallurgy and EB. PVD methods such as performance compared to chemical vapor deposition of metal rhenium prepared material better. China Kunming precious metal chemical vapor deposition method successfully prepared by rhenium. Iridium combustion chamber, but there is a certain distance away from the utility.

3 Conclusion
Now it seems that the main purpose of rhenium in the petrochemical industry, aerospace, metallurgical industry and so on, how to develop new application areas for further development in the future is the goal, and the preparation of rhenium alloys are mainly electrochemical deposition, powder metallurgy , electron beam. Physical vapor deposition, chemical vapor deposition method, the four basic manufacturing method have their own advantages, but the combination of product requirements, performance requirements, and the preparation of operational and manufacturing costs, the chemical vapor deposition method should be one of the more desirable, and also
It is currently the most promising method of manufacturing technology.

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