metal atoms of layers lying directly over one another (i.e. not close packed), with carbon atoms filling half the interstices giving both tungsten and carbon a regular trigonal prismatic, 6 coordination. From the unit cell dimensions the following bond lengths can be determined: the distance between the tungsten atoms in a hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The tungsten-carbon bond length is therefore comparable to the single bond in (218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten. Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for . Applications Cutting tools for machining Sintered tungsten carbide–cobalt cutting tools are very abrasion resistant and can also withstand higher temperatures than standard high-speed steel (HSS) tools. Carbide cutting surfaces are often used for machining tough materials such as carbon steel or stainless steel, and in applications where steel tools would wear quickly, such as high-quantity and high-precision production. Because carbide tools maintain a sharp cutting edge better than steel tools, they generally produce a better finish on parts, and their temperature resistance allows faster machining. The material is usually called cemented carbide, solid carbide, hardmetal or tungsten-carbide cobalt. It is a metal matrix composite, where tungsten carbide particles are the aggregate, and metallic cobalt serves as the matrix. It has been found wear and oxidation properties of cemented carbide can be improved by replacing cobalt with Iron Aluminide. Ammunition Tungsten carbide, in its monolithic sintered form, or much more often in cemented tungsten carbide cobalt composite (see above), is often used in armor-piercing ammunition, especially where depleted uranium is not available or is politically unacceptable. projectiles were first used by German Luftwaffe tank-hunter squadrons in World War II. However, owing to the limited German reserves of tungsten, material was reserved for making machine tools and small numbers of projectiles. It is an effective penetrator due to its combination of great hardness and very high density. Tungsten carbide ammunition is now generally of the sabot type. SLAP, or saboted light armour penetrator, where a plastic sabot discards at the barrel muzzle, is one of the primary types of saboted small arms ammunition. Non-discarding jackets, regardless of the jacket material, are not perceived as sabots but as bullets. Both of