décarburation

Décarburation, also known as decarburization, is a heat treatment process that alters the surface composition of ferrous metals, particularly steel. It involves the loss of carbon from the surface layer of the material. This occurs when steel is heated in an environment that contains oxygen or other carbon-depleting gases, such as in a furnace atmosphere that is not properly controlled. The carbon atoms in the steel react with these gases and diffuse out of the metal, leaving behind a layer that is depleted of carbon.

The extent of décarburation depends on several factors, including the temperature, the duration of the heating process, and the composition of the furnace atmosphere. Higher temperatures and longer exposure times generally lead to deeper and more severe décarburation. This phenomenon is undesirable in many applications because the loss of carbon from the surface can significantly reduce the hardness, strength, and wear resistance of the material. For components requiring a hard, wear-resistant surface, such as gears, tools, and bearings, décarburation can render them unfit for their intended purpose.

To mitigate décarburation, steel is often heat-treated in controlled atmospheres that are inert or carburizing, meaning they either don't react with the carbon or actually add carbon to the surface. Alternatively, protective coatings can be applied to the steel before heat treatment. In some specialized cases, a controlled amount of surface decarburization might be intentionally induced to achieve specific material properties. However, in most metallurgical applications, preventing or minimizing décarburation is a critical aspect of achieving the desired performance characteristics of steel components.