Tungsten powdeer metallurgy

Tungsten has the advantages of high melting point, high density, high strength, high wear resistance, low thermal expansion coefficient, good corrosion resistance and oxidation resistance [30], pure tungsten, and ultra-high density tungsten materials in the national defense military industry, aerospace, atomic energy and nuclear industry, electronic information, and other industries have a wide range of important applications. For example, high-density tungsten alloy is used as the small arrows of cluster arrows, shotshells, submunitions, screen bullets, and armor-piercing bullets, etc., with great killing power; tungsten and tungsten alloy materials, in missiles, are used as gyro-rotors of navigation instruments, counterweight screws, adjusting pieces; In nuclear submarines and nuclear-powered aircraft carriers, it is used to protect the core power part, while playing a good role of ray shielding; in electric heating processing, it is used as electrode materials and electric contact materials, etc. However, tungsten is difficult to sinter and difficult to process the intrinsic properties, so its application is limited.

Powder Injection Molding (PIM) technology is a new component manufacturing technology combining traditional plastic injection molding technology and powder metallurgy technology, which can form metals, alloys, ceramics, and composite materials like plastic forming [5]. PIM technology makes it easy to achieve low-cost large-scale production of parts with complex three-dimensional structures, so it has quickly become a hot research topic of manufacturing technology in today’s world.

Tungsten Powder Metallurgy

Research progress of PIM tungsten

Tungsten alloy has been widely used in cutting-edge science and technology and military industry, such as the core material of rod-type kinetic energy piercing projectile, balance weight element, inertia element, ray shielding material, and so on

In the preparation of bomb materials, the traditional press-sintering method can only produce simple-shaped products of tungsten alloy. PIM technology is used to manufacture high-density tungsten alloy materials for bombs, which solves the contradiction between the difficult processing of fragile tungsten alloy materials and the fragmentation of armor penetration, and reduces the consumption of raw materials.

In the civil field, Fe-Ni-tungsten alloy is used to prepare a micro-gear mold for powder injection molding by combining lithography technology and electroforming technology, and the life of the mold is greatly improved. Powder injection molding using 95W-3.5Ni-1.5Te as the material has been widely used.

PIM pure tungsten research

At present, the traditional pure tungsten or nearly pure tungsten materials generally use die-pressing – powder metallurgy high-temperature sintering preparation of blanks, and then complex machining, serious energy consumption, high manufacturing costs, raw material waste, very low yield, so the use of powder injection molding technology directly preparation of ultra-high density, ultra-high shape complexity of tungsten parts has become inevitable development.

Pure tungsten injection molding adding nanometer tungsten powder and optimizing the design of multi-particle powder composition method, with high-reliability pure tungsten electrode as the target application, has a good effect. Tungsten metal powder injection molding technology, through the powder and feed preparation, injection and degreasing, sintered at 1700°C, the density of the material can be higher than 98.3%, and the grain size is less than 2um.

Tungsten Powder Metallurgy

Powder injection molding technology is used in the separator, which is mainly used to manufacture tungsten and tungsten alloy components. The two-step sintering process was adopted. Firstly, pre-sintering at 1000°C under a hydrogen atmosphere for 2h was carried out to achieve the porosity required in the next step. Then the isostatic pressure was carried out for 3h in an argon atmosphere at 1600°C and 2500MPa. The tungsten element density of the separator is greater than 98%, the shrinkage rate of the product is 20%, the microstructure is fine and uniform, the hardness is high, and the section has no visible holes and cracks. This new structure design of key tungsten parts and powder injection molding technology put forward a higher and more urgent demand and will promote the development and progress of powder injection molding technology.

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