Editing Carburizing (section)

{{short description|Heat treatment process in which a metal or alloy is infused with carbon to increase hardness}}
{{Distinguish|Carbonization|Carburation|Carbonation}}
[[File:Computerised Heat Treatment Furnance.jpg|thumb|A modern computerised gas carburising furnace]]

'''Carburizing''', or '''carburising''', is a [[heat treatment]] process in which [[iron]] or [[steel]] absorbs [[carbon]] while the metal is heated in the presence of a carbon-bearing material, such as [[charcoal]] or [[carbon monoxide]]. The intent is to make the metal [[Hardness|harder]] and more wear resistant.<ref>{{cite web|url=http://encyclopedia2.thefreedictionary.com/Carburizing+of+Steel|title=Carburizing of Steel|publisher=The Free Dictionary By Farlex|access-date=2012-05-25|archive-url=https://web.archive.org/web/20110831165255/http://encyclopedia2.thefreedictionary.com/Carburizing+of+Steel|archive-date=2011-08-31|url-status=dead}}</ref> Depending on the amount of time and temperature, the affected area can vary in carbon content. Longer carburizing times and higher temperatures typically increase the depth of carbon diffusion. When the iron or steel is cooled rapidly by [[quenching]], the higher carbon content on the outer surface becomes hard due to the transformation from [[austenite]] to [[martensite]], while the core remains soft and tough as a [[ferritic]] and/or [[pearlite]] [[microstructure]].<ref>Oberg, E., Jones, F., and Ryffel, H. (1989) ''Machinery's Handbook 23rd Edition.'' New York: Industrial Press Inc.</ref>

This manufacturing process can be characterized by the following key points: It is applied to low-carbon workpieces; workpieces are in contact with a high-carbon gas, liquid or solid; it produces a hard workpiece surface; workpiece cores largely retain their [[toughness]] and [[ductility]]; and it produces [[case hardening|case hardness]] depths of up to {{convert|0.25|in}}. In some cases it serves as a remedy for undesired [[decarburization]] that happened earlier in a manufacturing process.