Production of Tungsten and Tungsten Carbide Powders

B. Lux, Vienna University of Technology; B. Zeiler, Wolfram Bergbau- und Huetten-GmbH Nfg KG

Tungsten gained major industrial importance at the beginning of the 20th century due to its technical application as alloying element in high-speed steel and as filament wire in incandescent lamps (Ref 1, 2, 3). For both applications, pure tungsten was produced in powder form. From 1900 to 1912 only pure tungsten powders were used in high amounts for high-speed steels containing 16 to 24% tungsten (Ref 1). This application dominated the tungsten consumption at the time, but around 1915 ferrotungsten replaced the tungsten metal powder in this application.

Later (1910-1920), diamonds were needed in large numbers to produce drawing dies for tungsten lamp wire fabrication. Due to their high costs, there was a strong driving force to find cheaper alternatives. At this time, the very hard tungsten carbides (WC and W2C), studied by Henri Moissan at the end of the 19th century during his attempts to make artificial diamond (Ref 3, 4), were considered as appropriate alternatives. However, all trials to compact tungsten carbide powders resulted in porous and brittle products unusable for the anticipated drawing dies application. In 1922, researchers of the OSRAM study group combined the brittle tungsten carbide with a ductile metal binder (iron, cobalt). After sintering the respective powder mixtures, a material of both high strength and toughness was obtained. Thus the "hardmetal" also named "cemented carbide" was created. OSRAM used the new material mainly for wire drawing. Since they apparently did not yet realize the great importance of their invention, patents were applied for in only Germany, Great Britain, and the United States, while in all other countries, priority deadlines were missed (Ref 3).

In 1925 KRUPP, a company experienced in steel technology and tool manufacturing, realized the enormous potential of the hardmetals and bought the patent rights. In 1927 they introduced hardmetals under the brand name WIDIA (an abbreviation for WI-e DIA-mant, which in German means "similar to diamond") (Ref 3). Since then, cemented carbides have changed the tungsten consumption pattern completely; today, hardmetals (and thus tungsten carbide powders) account for more than half of the world's tungsten consumption (Ref 5, 6, 7, and 8).

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