Tungsten carbide is interstitial carbide.
Interstitial carbides are formed mostly by transition elements, and some of the lanthanides and actinides. In interstitial carbides, the small carbon atoms occupy interstitial positions in the crystal lattice of the metal. Interstitial carbides are characterised by opacity, metallic lustre, and high electrical conductivity. They retain many of the properties of metals and conduct electricity by metallic conduction. They are hard, high melting, and chemically inert.