Carbide

Carbide refers to a wide class of compounds in which carbon is chemically combined with an element more electropositive than carbon. Most commonly these are inorganic binary compounds such as tungsten carbide (WC) and silicon carbide (SiC), but the term also includes more complex materials such as cemented carbides, where carbide grains are bound in a metal matrix, and compounds like calcium carbide (CaC2).

Carbide types and examples include binary inorganic carbides such as WC, SiC, titanium carbide (TiC), vanadium carbide (VC), and chromium carbide (Cr3C2). A notable category is cemented carbides (hard metals), formed by sintering carbide grains in a cobalt or nickel binder. Calcium carbide is produced industrially by reacting lime with coke at high temperature to yield CaC2 and carbon monoxide.

Carbides generally exhibit high hardness, high melting points, and good chemical stability at elevated temperatures. They can be brittle, but the metal binder in cemented carbides provides some toughness. Manufacturing methods vary: many carbides form by direct reaction at high temperatures; cemented carbides are made by powder metallurgy and subsequent sintering.

Applications are broad. Carbides are widely used as cutting tools, wear-resistant parts, and abrasives, and as refractory components in high-temperature environments. Silicon carbide, in particular, is used in high-power electronics, semiconductors, and LED technology. Calcium carbide is used to produce acetylene gas and as a chemical reagent.

Occurrence and safety: Cementite (Fe3C) is a carbide phase that occurs in steel. Some natural carbides exist as minerals such as cohenite. Calcium carbide reacts with water to release acetylene, a flammable gas, requiring careful handling and proper ventilation.