Editing Carburizing (section)

== Method ==
Carburization of steel involves a heat treatment of the metallic surface using a source of carbon.<ref name="Low-carbon steels">{{cite web| url= http://www.efunda.com/materials/alloys/carbon_steels/low_carbon.cfm|title=Low-carbon steels|publisher= efunda |access-date=2012-05-25}}</ref> Carburization can be used to increase the surface hardness of low carbon steel.<ref name="Low-carbon steels"/>

Early carburization used a direct application of [[charcoal]] packed around the sample to be treated (initially referred to as [[case hardening]]), but modern techniques use carbon-bearing gases or plasmas (such as [[carbon dioxide]] or [[methane]]). The process depends primarily upon ambient gas composition and furnace temperature, which must be carefully controlled, as the heat may also impact the microstructure of the remainder of the material. For applications where great control over gas composition is desired, carburization may take place under very low pressures in a [[vacuum]] chamber.

Plasma carburization is increasingly used to improve the surface characteristics (such as wear, [[corrosion]] resistance, [[hardness]], load-bearing capacity, in addition to quality-based variables) of various metals, notably [[stainless steel]]s. The process is environmentally friendly (in comparison to gaseous or solid carburizing). It also provides an even treatment of components with complex geometry (the plasma can penetrate into holes and tight gaps), making it very flexible in terms of component treatment.

The process of carburization works via the diffusion of carbon atoms into the surface layers of a metal. As metals are made up of atoms bound tightly into a metallic [[crystalline lattice]], the carbon atoms diffuse into the crystal structure of the metal and either remain in solution (dissolved within the metal crystalline matrix — this normally occurs at lower temperatures) or react with elements in the host metal to form carbides (normally at higher temperatures, due to the higher mobility of the host metal's atoms). If the carbon remains in solid solution, the steel is then heat treated to harden it. Both of these mechanisms strengthen the surface of the metal, the former by forming pearlite or martensite, and the latter via the formation of carbides. Both of these materials are hard and resist abrasion. 

Gas carburizing is normally carried out at a temperature within the range of 900 to 950&nbsp;°C.

In [[Oxy-fuel welding and cutting|oxy-acetylene welding]], a carburizing flame is one with little oxygen, which produces a [[soot]]y, lower-temperature flame. It is often used to [[Annealing (metallurgy)|anneal]] metal, making it more malleable and flexible during the welding process.

A main goal when producing carburized workpieces is to ensure maximum contact between the workpiece surface and the carbon-rich elements. In gas and liquid carburizing, the workpieces are often supported in mesh baskets or suspended by wire.  In pack carburizing, the workpiece and carbon are enclosed in a container to ensure that contact is maintained over as much surface area as possible. Pack carburizing containers are usually made of carbon steel coated with aluminum or heat-resisting nickel-chromium alloy and sealed at all openings with fire clay.

Carburizing can be achieved in either a Conventional Furnace (Atmosphere Furnace) or a Low Pressure Carburizing Furnace (LPC).<ref>{{Cite web |title=Low Pressure Carburizing vs. Atmospheric Furnace Technology |url=https://www.ecm-usa.com/resources/lpc-comparison |access-date=2024-08-19 |website=ECM USA Vacuum Furnace Systems Manufacturer |language=en-US}}</ref>

* Conventional Furnace (Atmosphere Furnace): conventional carburizing is an atmosphere controlled process with control of the carbon potential.
* Low Pressure Carburizing Furnace (LPC): low pressure carburizing is running without any oxygen and with injections of carburizing gas (ex. [[acetylene]]).