Molybdenum and its alloys
Chemical properties of the metal molybdenum
Molybdenum has two outer electron layers, N layers and O layers, which are not filled with electrons. This structure enables molybdenum to have a variety of chemical valence states and can form a wide variety of compounds. The chemical properties of molybdenum in the air are very stable at room temperature, and it will not be corroded by hydrochloric acid, hydrofluoric acid and lye, but it can be dissolved in concentrated sulfuric acid, nitric acid and aqua aqua. When the temperature reaches 400℃, slight oxidation will occur. When the temperature is higher than 600℃, molybdenum metal will rapidly oxidize to molybdenum trioxide. Above 700℃, steam strongly oxidizes molybdenum to form molybdenum dioxide.
Preparation of molybdenum powder
The industrialized production of molybdenum powder mainly adopts the traditional system of the process, usually in molybdenum dioxide and molybdenum oxide or ammonium molybdate as raw materials, in the fixed bed or fluidized bed type reduction device, with hydrogen reduction method to manufacture metal molybdenum powder, molybdenum powder particle size in the output of micron level, mainly applied to the general press system of molybdenum materials and all other raw materials of powder metallurgy products. The traditional manufacturing process of molybdenum powder has the advantages of low cost and easy industrial production. However, it also has the disadvantages of long production cycle and high temperature. Molybdenum powders with different particle size, morphology and oxygen content can be obtained by using different raw materials and different processes.
Any of several alloys of molybdenum
Molybdenum and molybdenum alloy single crystal
Molybdenum and molybdenum alloy single crystal have toughening brittle transition temperature is low, there is no high and low temperature grain boundary destruction, and nuclear materials have good compatibility and high temperature performance is stable, can significantly improve the stability and reliability of the components used and the working life, so is widely used in electronics, machinery, high-tech areas like nuclear power industry. In recent years, with the rapid development of science and technology, the application fields of molybdenum and molybdenum alloy single crystal are expanding.
Molybdenum rhenium alloy
Due to the so-called "rhenium effect", the properties of molybdenum-rhenium alloys have been greatly improved, so that the strength, plasticity and weldability of the alloy are increased at the same time, and the alloy has a low ductile-brittle transition temperature resistance, so molybdenum-rhenium alloys have been widely used in aerospace and electronics industries and other fields. The results show that the molybdenum-rhenium alloy with 11%~50% rhenium has the best performance, and the alloy with 40%~50% rhenium has the most wide use.
In recent years, researchers at the U.S. Department of Energy have developed several new molybdenum-rhenium alloys. Among them, the most notable is the ODS molybdenum-rhenium alloy, namely lanthanum oxide, cerium oxide or reinforced molybdenum-rhenium alloy. The new method of producing molybdenum alloy is to shop molybdenum oxide, nitric acid, acetate (or mace) dispersed in water solution, the hydrogen environment, heat the molybdenum oxide and lanthanum nitrate reduction for molybdenum powder and lanthanum oxide, add the rhenium powder blend to suppress, and then burn up alloy ingot in hydrogen atmosphere, the final will be alloy ingot and forming, which get the shovel molybdenum alloy containing copper oxide. The alloy has high strength, good workability and high temperature properties.
Molybdenum Titanium Zirconium (TZM) alloy
TZM alloy is a superalloy formed by adding a certain amount of Ti and Zr to molybdenum. The addition of Ti and Zr makes the Mo-Ti solid solution and the dispersed particles appear in the molybdenum matrix, so the solid solution strengthening of the Mo-Ti solid solution and the dispersion strengthening of the TiC particles in the molybdenum matrix are obtained.
TZM alloy has the characteristics of high melting point, high strength, good elastic modulus, small linear expansion coefficient, low vapor, good electrical and thermal conductivity, strong corrosion resistance and good high temperature mechanical properties, so it has been widely used in many fields:
Its good mechanical properties under high temperature and pressure make it widely used in military industry, such as torpedo engine valve body, rocket nozzle, gas pipeline, nozzle throat lining;
Its corrosion resistance to metallic liquid is used as the main shaft of the glass furnace agitator in the production line of color kinescope glass shell coated);
It has a high melting point, so it can be used to make black or non-ferrous metal die casting material and seamless stainless steel pipe perforation
Head;
TZM alloy plate is widely used as furnace wall of high temperature furnace and heat insulation screen of hot isostatic press.
The alloy can be used as cathode, gate, high voltage rectifier element and so on in electronic and electrical industry.
It is used as radiation cover, support frame, heat exchanger, rail and so on in nuclear energy equipment.
