Surface Engineering by Expanded Austenite
History of Carburising
Origins
The history of carburising began over a thousand years ago; dating back to the Roman era, where the black smiths would lay their swords in a bed of burning charcoal for an extended period of time before quenching them in water to harden the steel and then reheating the swords to temper the blade to reduce the brittleness of the sword to avoid shattering during large impacts. However back then they were unaware that by placing the sword in the charcoal it was not only just heating up the sword to high temperatures but the charcoal was also acting as a carbon donor, carburising the surface of the steel.
During the industrial revolution in the 19th century, more was understood about the carburising process, where they would place the steel in a box of ground charcoal powder and anthracitic coal and in a furnace of high temperature. At the beginning of the 20th century the technology moved to dipping the steel into a salt melt, where an activator would diffuse the carbon and nitrogen through the surface of the steel. Since the 1960’s controlled gas carburising has been the most popular method. This process involves high temperature, low pressure gaseous mixture with hydrocarbons as the main carbon donor and then quenching the steel in high pressure gas which is a more environmentally friendly option than quenching the steel in oil or aqueous solution.
