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Ferritic nitrocarburizing or, less commonly known as Ferritic nitrocarburising, in British English, is a range of case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures. The processing temperature ranges from to , but usually occurs at . At this temperature steels and other ferrous alloys are still in a ferritic phase, which is advantageous compared to other case hardening processes that occur in the austenitic phase.〔.〕 There are four main classes of ferritic nitrocarburizing: ''gaseous'', ''salt bath'', ''ion'' or ''plasma'', and ''fluidized-bed''.〔.〕 The process is used to improve three main surface integrity aspects: * scuffing resistance * fatigue properties * corrosion resistance It has the added advantage of inducing little shape distortion during the hardening process. This is because of the low processing temperature, which reduces thermal shocks and avoids phase transitions in steel.〔.〕 ==History== The first ferritic nitrocarburizing methods were done at low temperatures, around , in a liquid salt bath. The first company to successfully commercialize the process was the Imperial Chemical Industries in Great Britain. ICI called their process "the cassel" due to the plant where it was developed 〔https://www.youtube.com/watch?v=yt2DU-22qus〕〔https://books.google.co.uk/books/about/The_Cassel_Sulfinuz_Process.html?id=QUzmMgEACAAJ&hl=enor〕 or "Sulfinuz" treatment because it had sulfur in the salt bath. While the process was very successful with high-speed spindles and cutting tools, there were issues with cleaning the solution off because it was not very water soluble.〔.〕 Because of the cleaning issues the Joseph Lucas Limited company began experimenting with gaseous forms of ferritic nitrocarburizing in the late 1950s. The company applied for a patent by 1961. It produced a similar surface finish as the Sulfinuz process with the exception of the formation of sulfides. The atmosphere consisted of ammonia, hydrocarbon gases, and a small amount of other carbon-containing gases.〔.〕 This spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents.〔http://global-heat-treatment-network.com/en/hans-veltrops-page〕 Their process is the widely known as the Tufftride or Tenifer process. Following this the ion nitriding process was invented in the early 1980s. This process had faster cycle times, required less cleaning and preparation, formed deeper cases, and allowed for better control of the process.〔.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ferritic nitrocarburizing」の詳細全文を読む スポンサード リンク
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