Tungsten powder is powdered metallic tungsten, a core raw material for preparing tungsten processed materials, tungsten alloys, and tungsten products, playing an irreplaceable role in the industrial system. Based on particle size, morphology, and processing differences, it can be classified into different types, including ordinary tungsten powder, crystalline tungsten powder, spherical tungsten powder, doped tungsten powder, and nano-tungsten carbide powder, to meet the needs of various applications.

Basic Physicochemical Properties

Physical Properties: It appears as a grayish-black powder with a metallic luster, and its crystal structure is body-centered cubic. Its melting point is 3400℃, and its boiling point is 5555℃, making it the metallic element with the highest known melting point. Its hardness is the highest among all metals; sintered tungsten bars can reach a hardness of 200–250, and tungsten rods processed by rotary hammer can reach a hardness of 350–400.

Chinese national standards classify tungsten powder into 14 grades based on particle size. The conventional particle size range is 0.4–30 micrometers, and the average Fisher's density of commonly used tungsten powder is 2–10 μm. The particles are polygonal, and there are clear standard requirements for oxygen content, loose density, and tap density. The characteristics of some specialty tungsten powders are as follows:

Crystallic tungsten powder (coarsest grade): FSSS particle size can reach 35~40μm, Scott density 7.3~8.9g/cm³, good flowability, low oxygen content;
Doped tungsten powder: Average particle size is stable at 2~5μm, with added potassium, aluminum, silicon, etc., used for processing specialty tungsten products.

Chemical properties: Soluble in a mixture of nitric acid and hydrofluoric acid; molten with a mixture of sodium hydroxide and sodium carbonate; slightly soluble in nitric acid, sulfuric acid, and aqua regia; insoluble in water, hydrofluoric acid, and potassium hydroxide. Under standard temperature and pressure, the α-type body-centered cubic structure is stable; β-type tungsten can only exist under aerobic conditions, is stable below 630℃, and irreversibly transforms into α-type tungsten above 630℃.

Mainstream Production Processes
The most common industrial method for preparing tungsten powder is the hydrogen reduction method, which consists of two main stages:

The first stage involves reducing tungsten trioxide to tungsten dioxide at 500–700℃;

The second stage involves reducing tungsten dioxide to tungsten powder at 700–900℃. This reduction is typically carried out in a tubular electric furnace or rotary furnace.

Alternatively, ammonium paratungstate can be first reduced to blue tungsten oxide (blue tungsten) before being reduced with hydrogen to obtain tungsten powder, which allows for better control of particle size.

Different process optimizations are available to meet specific needs:

**Crystalled Tungsten Powder:** Using blue tungsten as the main raw material (≥70%), a hydrogen reduction process with hydrogen purity >99.5% and dew point <-40℃ is employed. The process involves batching and mixing, molybdenum wire furnace reduction, ball milling, washing, and drying to obtain ultra-coarse tungsten powder with uniform particle size.

**Ultrafine/Nano Tungsten Powder:** Ultrafine tungsten powder with a particle size less than 0.05μm can be obtained using the tungsten chloride hydrogen reduction method. Nano-tungsten carbide powder can be prepared through plasma-assisted ball milling activation carbonization, enabling carbonization synthesis at relatively low temperatures.

**Doped Tungsten Powder:** Primarily prepared using spray drying combined with a two-step hydrogen reduction method. The properties of the tungsten matrix are optimized by adding different dopants. In recent years, a fluorine-free acid washing process has also been developed, making it more environmentally friendly.

Main Application Areas

Different types of tungsten powder have different application focuses:

**General-purpose tungsten powder:** Mostly used in the production of cemented carbide and ferrotungsten. It can be used to prepare tungsten carbide powder for machining cemented carbide tools such as lathe tools, milling cutters, drill bits, and molds. Pure tungsten powder can also be used to make tungsten wires, rods, and plates for use in light bulb filaments, electron tube components, and arc welding electrodes. It can also be mixed with other metal powders to prepare special tungsten alloys such as tungsten-copper, tungsten-silver, tungsten-molybdenum, and tungsten-rhenium, which are used as electrical contact materials, high-temperature components, and radiation shielding. Different grades correspond to specific applications: FW-1 is used for large slabs and tungsten-rhenium thermocouple raw materials; FW-2 is used for contact alloys and high-density shielding materials; FWP-1 is used for plasma spraying materials.

**Crystalline tungsten powder:** This is a coarse-grained tungsten powder, mainly used in oil drilling tool matrix materials, hardfacing materials, wear-resistant component coatings, and in the spraying of tungsten pots for medium-frequency furnaces. Nano-tungsten carbide powder: Used to prepare high-performance cemented carbides and wear-resistant coatings. After processing with supersonic flame spraying, it is widely used in aerospace, metallurgy, petrochemical, and machinery industries, significantly improving the wear resistance and service life of the coating.

Doped tungsten powder: Primarily used in the production of tungsten rods, tungsten wires, and tungsten-molybdenum alloys, especially for manufacturing anti-sagging doped tungsten wires. It can also be used as a high current density cathode material in applications such as emitter cathodes and semiconductor components. By adding special dopants, the electron work function can be reduced, improving emission stability and service life.