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{{Short description|Type of hardening with nitrogen and carbon using a salt bath}}
{{distinguish|Carbonitriding}}
{{distinguish|Carbonitriding}}


'''Ferritic nitrocarburizing''', also known by the proprietary names '''Tennifer'''/ '''Tenifer''' and '''Melonite''',<ref group=Note>Other trade names include Tuffride/ Tuffrider, Sulfinuz, Sursulf, Meli 1, and Nitride, among others</ref><ref name="Totten2006">{{cite book|author=George E. Totten|title=Steel Heat Treatment: Metallurgy and Technologies|url=https://books.google.com/books?id=DVfLBQAAQBAJ&pg=PA530|date=28 September 2006|publisher=CRC|isbn=978-0-8493-8452-3|page=530}}</ref> is a range of proprietary [[case hardening]] processes that diffuse [[nitrogen]] and [[carbon]] into [[ferrous]] metals at sub-[[critical temperature]]s during a salt bath.<ref group=Note>Other methods of ferric nitrocarburizing include gaseous process such as [[Nitrotec]] and ion (plasma) ones such as [[Oxynit]].</ref> The processing temperature ranges from {{convert|525|°C|°F}} to {{convert|625|°C|°F}}, but usually occurs at {{convert|565|°C|°F}}. 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.<ref name="pye">{{Harvnb|Pye|2003|p=193}}.</ref> There are four main classes of ferritic nitrocarburizing: ''gaseous'', ''salt bath'', ''ion'' or ''plasma'', and ''fluidized-bed''.<ref name="pye202">{{Harvnb|Pye|2003|p=202}}.</ref>
'''Ferritic nitrocarburizing''' or '''FNC''', also known by the proprietary names "Tenifer", "Tufftride", Melonite, and "Arcor",<ref group=Note>Other trade names include Tuffride/ Tuffrider, QPQ, Sulfinuz, Sursulf, Meli 1, and Nitride, among others</ref><ref name="Totten2006">{{cite book|first=George E. |last=Totten |title=Steel Heat Treatment: Metallurgy and Technologies |url= https://books.google.com/books?id=DVfLBQAAQBAJ&pg=PA530 |date=28 September 2006 |publisher=CRC |isbn=978-0-8493-8452-3 |page=530}}</ref> is a range of proprietary [[case hardening]] processes that diffuse [[nitrogen]] and [[carbon]] into [[ferrous]] metals at sub-[[critical temperature]]s during a salt bath. Other methods of ferritic nitrocarburizing include gaseous processes such as Nitrotec and ion (plasma) ones. The processing temperature ranges from {{convert|525|°C|°F}} to {{convert|625|°C|°F}}, but usually occurs at {{convert|565|°C|°F}}. Steel and other ferrous alloys remain in the [[Allotropes of iron#Alpha iron (α-Fe)|ferritic]] phase region at this temperature. This allows for better control of the dimensional stability that would not be present in case hardening processes that occur when the alloy is transitioned into the [[austenitic]] phase.<ref name="pye">{{Harvnb|Pye|2003|p=193}}.</ref> There are four main classes of ferritic nitrocarburizing: ''gaseous'', ''salt bath'', ''ion'' or ''plasma'', and ''fluidized-bed''.<ref name="pye202">{{Harvnb|Pye|2003|p=202}}.</ref>


The process is used to improve three main [[surface integrity]] aspects including scuffing resistance, [[fatigue (material)|fatigue]] properties, and [[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 transition]]s in steel.<ref>{{Harvnb|Pye|2003|pp=193–194}}.</ref>
The process improves three main [[surface integrity]] aspects: scuffing resistance, [[fatigue (material)|fatigue]] properties, and [[corrosion resistance]]. It has the 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 transition]]s in steel.<ref>{{Harvnb|Pye|2003|pp=193–194}}.</ref>


==History==
==History==
The first ferritic nitrocarburizing methods were done at low temperatures, around {{convert|550|C|abbr=on}}, 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 <ref>https://www.youtube.com/watch?v=yt2DU-22qus</ref><ref>https://books.google.com/books?id=QUzmMgEACAAJ&hl=enor</ref> or "Sulfinuz" treatment because it had sulfur in the salt bath. While the process was very successful with high-speed spindles and [[cutting tool]]s, there were issues with cleaning the solution off because it was not very water [[soluble]].<ref>{{Harvnb|Pye|2003|p=195}}.</ref>
The first ferritic nitrocarburizing methods were done at low temperatures, around {{convert|550|C|abbr=on}}, 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<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211205/yt2DU-22qus Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20200927155348/https://www.youtube.com/watch?v=yt2DU-22qus&gl=US&hl=en Wayback Machine]{{cbignore}}: {{cite AV media |url=https://www.youtube.com/watch?v=yt2DU-22qus |title=ICI End of Process – Castner Process at Cassel Works |publisher=Transfilm UK |via=YouTube}}{{cbignore}}</ref><ref>{{cite book |url=https://books.google.com/books?id=QUzmMgEACAAJ |title=The 'Cassel' 'Sulfinuz' Process |publisher=Imperial Chemical Industries |year=1954}}</ref> or "Sulfinuz" treatment because it had sulfur in the salt bath. While the process was very successful with high-speed spindles and [[cutting tool]]s, there were issues with cleaning the solution off because it was not very water-[[soluble]].<ref>{{Harvnb|Pye|2003|p=195}}.</ref>


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.<ref>{{Harvnb|Pye|2003|pp=195–196}}.</ref>
Because of the cleaning issues, [[Lucas Industries]] began experimenting with gaseous forms of ferritic nitrocarburizing in the late 1950s. The company applied for a patent in 1961. It produced a similar surface finish as the Sulfinuz process, except for the formation of sulfides. The atmosphere consists of [[ammonia]], [[hydrocarbon]] gases, and a small amount of other carbon-containing gases.<ref>{{Harvnb|Pye|2003|pp=195–196}}.</ref>


This spurred the development of a more environmentally friendly salt bath process by the German company [[Degussa]] after acquiring ICI patents.<ref>{{cite web|title=To find the way in the nomenclature jungle of nitrogen diffusion|url=http://global-heat-treatment-network.com/en/hans-veltrops-page|author=Hans Velstrop|date=22 February 2015</ref> 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.<ref>{{Harvnb|Pye|2003|pp=196–197}}.</ref>
This innovation spurred the development of a more environmentally friendly salt bath process by the German company [[Degussa]] after acquiring ICI patents.<ref>{{cite web|title=To find the way in the nomenclature jungle of nitrogen diffusion |url= http://global-heat-treatment-network.com/en/hans-veltrops-page |first=Hans |last=Velstrop |date=22 February 2015}}</ref> Their process is 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.<ref>{{Harvnb|Pye|2003|pp=196–197}}.</ref>


==Processes==
==Processes==
Despite the naming the process is a modified form of [[nitriding]] and not [[carburizing]]. The shared attributes of this class of this process is the introduction of nitrogen and carbon in the ferritic state of the material. The processes are broken up into four main classes: ''gaseous'', ''salt bath'', ''ion'' or ''plasma'', or ''fluidized-bed''. The trade name and patented processes may vary slightly from the general description, but they are all a form of ferritic nitrocarburizing.<ref>{{Harvnb|Pye|2003|pp=201–202}}.</ref>
Despite the naming, the process is a modified form of [[nitriding]] and not [[carburizing]]. The shared attribute of this class of this process is the introduction of nitrogen and carbon in the ferritic state of the material. The processes are divided into four main classes: ''gaseous'', ''salt bath'', ''ion'' or ''plasma'', or ''fluidized-bed''. The trade name and patented processes may vary slightly from the general description, but they are all a form of ferritic nitrocarburizing.<ref>{{Harvnb|Pye|2003|pp=201–202}}.</ref>


===Salt bath ferritic nitrocarburizing===
===Salt bath ferritic nitrocarburizing===
Salt bath ferritic nitrocarburizing is also known as '''liquid ferritic nitrocarburizing''' or '''liquid nitrocarburizing'''<ref name="easterday">{{Citation|last=Easterday |first=James R. |title=Liquid Ferritic Nitrocarburizing |url=http://domino-69.prominic.net/A55B6F/nitromet/nitromet.nsf/a615da0219b54b79852571cb006bc9d2/d5e108115987d71c862572bc007000f7/$FILE/Nitromet%20Liquid%20Ferritic%20Nitrocarburizing.pdf |accessdate=2009-09-17 |deadurl=yes |archiveurl=https://web.archive.org/web/20110724021449/http://domino-69.prominic.net/A55B6F/nitromet/nitromet.nsf/a615da0219b54b79852571cb006bc9d2/d5e108115987d71c862572bc007000f7/$FILE/Nitromet%20Liquid%20Ferritic%20Nitrocarburizing.pdf |archivedate=2011-07-24 |df= }}.</ref> and is also known by the trademarked names '''Tufftride'''<ref name="pye202"/> and '''Tenifer'''.<ref>{{Citation|title=History of the company |url=http://www.durferrit.com/en/unternehmen/firmengeschichte.htm |accessdate=2009-09-29 |deadurl=yes |archiveurl=https://web.archive.org/web/20090826232057/http://www.durferrit.com:80/en/unternehmen/firmengeschichte.htm |archivedate=2009-08-26 |df= }}.</ref>
Salt bath ferritic nitrocarburizing is also known as liquid ferritic nitrocarburizing or liquid nitrocarburizing<ref name="easterday">{{cite web|last=Easterday |first=James R. |title=Liquid Ferritic Nitrocarburizing |url= http://domino-69.prominic.net/A55B6F/nitromet/nitromet.nsf/a615da0219b54b79852571cb006bc9d2/d5e108115987d71c862572bc007000f7/$FILE/Nitromet%20Liquid%20Ferritic%20Nitrocarburizing.pdf |website=domino-69.prominic.net |archive-url= https://web.archive.org/web/20110814212927/http://domino-69.prominic.net/A55B6F/nitromet/nitromet.nsf/a615da0219b54b79852571cb006bc9d2/d5e108115987d71c862572bc007000f7/$FILE/Nitromet%20Liquid%20Ferritic%20Nitrocarburizing.pdf |archive-date=14 August 2011 |access-date=19 August 2024}}.</ref> and is also known by the trademarked names "Tufftride"<ref name="pye202"/> and "Tenifer".<ref>{{citation |title=History of the company |url= http://www.durferrit.com/en/unternehmen/firmengeschichte.htm |access-date=2009-09-29 |archive-url= https://web.archive.org/web/20090826232057/http://www.durferrit.com/en/unternehmen/firmengeschichte.htm |archive-date=2009-08-26 }}.</ref>


The simplest form of this process is encompassed by the trademarked '''Melonite''' process, also known as '''Meli 1'''. It is most commonly used on steels, [[sintering|sintered]] irons, and [[cast iron]]s to lower [[friction]] and improve [[wear resistance|wear]] and corrosion resistance.<ref name="pye203">{{Harvnb|Pye|2003|p=203}}.</ref><ref>{{Citation|title = Melonite Processing|url = http://www.burlingtoneng.com/melonite.html|accessdate = 2009-09-17}}.</ref>
The simplest form of this process is encompassed by the trademarked "Melonite" process, also known as "Meli 1". It is most commonly used on steels, [[sintering|sintered]] irons, and [[cast iron]]s to lower [[friction]] and improve [[wear resistance|wear]] and corrosion resistance.<ref name="pye203">{{Harvnb|Pye|2003|p=203}}.</ref><ref>{{Citation|title = Melonite Processing |url = http://www.burlingtoneng.com/melonite.html |access-date = 2009-09-17}}.</ref>


The process uses a salt bath of [[alkali]] [[cyanate]]. This is contained in a steel pot that has an [[aeration]] system. The cyanate thermally reacts with the surface of the workpiece to form alkali [[carbonate]]. The bath is then treated to convert the carbonate back to a cyanate. The surface formed from the reaction has a compound layer and a diffusion layer. The compound layer consists of iron, nitrogen, and oxygen, is abrasion resistant, and stable at elevated temperatures. The diffusion layer contains [[nitride]]s and [[carbide]]s. The [[Vickers hardness|surface hardness]] ranges from 800 to 1500 HV depending on the [[steel grades|steel grade]]. This also inversely affects the depth of the case; i.e. a high carbon steel will form a hard, but shallow case.<ref name="pye203"/>
The process uses a salt bath of [[alkali]] [[cyanate]]. This is contained in a steel pot that has an [[aeration]] system. The cyanate thermally reacts with the surface of the workpiece to form an alkali [[carbonate]]. The bath is then treated to convert the carbonate back to a cyanate. The surface formed from the reaction has a compound layer and a diffusion layer. The compound layer consists of iron, nitrogen, and oxygen is abrasion resistant and is stable at elevated temperatures. The diffusion layer contains [[nitride]]s and [[carbide]]s. The [[Vickers hardness|surface hardness]] ranges from 800 to 1500 HV depending on the [[steel grades|steel grade]]. This also inversely affects the depth of the case; i.e., a high carbon steel will form a hard, but shallow case.<ref name="pye203"/>


A similar process is the trademarked '''Nu-Tride''' process, also known incorrectly as the '''Kolene''' process (which is actually the company's name), which includes a preheat and an intermediate quench cycle. The intermediate quench is an [[Oxidizing agent|oxidizing]] salt bath at {{convert|400|C|abbr=on}}. This quench is held for 5 to 20 minutes before final quenching to room temperature. This is done to minimize distortion and to destroy any lingering cyanates or cyanides left on the workpiece.<ref>{{Harvnb|Pye|2003|pp=208–210}}.</ref>
A similar process is the trademarked "Nu-Tride" process, also known incorrectly as the "Kolene" process (which is the company's name), includes a preheat and an intermediate quench cycle. The intermediate quench is an [[Oxidizing agent|oxidizing]] salt bath at {{convert|400|C|abbr=on}}. This quench is held for 5 to 20 minutes before the final quenching to room temperature. This is done to minimize distortion and to destroy any lingering cyanates or cyanides left on the workpiece.<ref>{{Harvnb|Pye|2003|pp=208–210}}.</ref>


Other trademarked processes are '''Sursulf''' and '''Tenoplus'''. Sursulf has a sulfur compound in the salt bath to create surface sulfides which creates [[porosity]] in the workpiece surface. This porosity is used to contain lubrication. Tenoplus is a two-stage high-temperature process. The first stage occurs at {{convert|625|C|abbr=on}}, while the second stage occurs at {{convert|580|C|abbr=on}}.<ref>{{Harvnb|Pye|2003|p=217}}.</ref>
Other trademarked processes are "Sursulf" and "Tenoplus". Sursulf has a sulfur compound in the salt bath to create surface sulfides creating [[porosity]] in the workpiece surface. This porosity is used to contain lubrication. Tenoplus is a two-stage high-temperature process. The first stage occurs at {{convert|625|C|abbr=on}}, while the second stage occurs at {{convert|580|C|abbr=on}}.<ref>{{Harvnb|Pye|2003|p=217}}.</ref>


===Gaseous ferritic nitrocarburizing===
===Gaseous ferritic nitrocarburizing===
Gaseous ferritic nitrocarburizing is also known as '''controlled nitrocarburizing''', '''soft nitriding''', and '''vacuum nitrocarburizing''' or by the tradenames '''Nitrotec''', '''Nitemper''', '''Deganit''', '''Triniding''', '''Corr-I-Dur''', '''Nitroc''', '''NITREG-C''' and '''Nitrowear''', '''Nitroneg'''.<ref name="pye202"/><ref>{{Harvnb|Pye|2003|p=220}}.</ref> The process works to achieve the same result as the salt bath process, except gaseous mixtures are used to diffuse the nitrogen and carbon into the workpiece.<ref name="pye219">{{Harvnb|Pye|2003|p=219}}.</ref>
Gaseous ferritic nitrocarburizing is also known as controlled nitrocarburizing, soft nitriding, and vacuum nitrocarburizing or by the tradenames "UltraOx",<ref>{{cite web |title=UltraOx |url= https://www.ahtcorp.com/services/nitriding-and-nitrocarburizing/ultraox/ |website=ahtcorp.com |access-date=16 January 2023}}</ref> "Nitrotec", "Nitemper", "Deganit", "Triniding", "Corr-I-Dur", "Nitroc", "Nitreg-C",<ref>{{cite web |title=nitrocarburizing Nitreg-C |url= https://www.nitrex.com/en/solutions/furnaces-technologies/nitriding-nitrocarburizing/nitreg-technologies/nitrocarburizing-nitreg-c/ |website=nitrex.com/en/ |access-date=19 August 2024}}</ref> "Nitrowear", and "Nitroneg".<ref name="pye202"/><ref>{{Harvnb|Pye|2003|p=220}}.</ref> The process works to achieve the same result as the salt bath process, except gaseous mixtures are used to diffuse the nitrogen and carbon into the workpiece.<ref name="pye219">{{Harvnb|Pye|2003|p=219}}.</ref>


The parts are first cleaned, usually with a [[vapor degreasing]] process, and then nitrocarburized around {{convert|570|C|abbr=on}}, with a process time that ranges from one to four hours. The actual gas mixtures are proprietary, but they usually contain ammonia and an [[endothermic]] gas.<ref name="pye219"/>
The parts are first cleaned, usually with a [[vapor degreasing]] process, and then nitrocarburized around {{convert|570|C|abbr=on}}, with a processing time that ranges from one to four hours. The actual gas mixtures are proprietary, but they usually contain ammonia and an [[endothermic]] gas.<ref name="pye219"/>

In comparison to a standard nitriding process, ferritic nitrocarburizing or FNC in a vacuum furnace takes less time to achieve case depth requirements - mainly in part due to the addition of carbon to achieve faster diffusion.<ref>{{cite web|url= https://www.ecm-usa.com/applications/ferritic-nitrocarburizing-fnc |title=Ferritic Nitrocarburizing (FNC) - Overview |website=ecm-usa.com |access-date=19 August 2024}}</ref>


===Plasma-assisted ferritic nitrocarburizing===
===Plasma-assisted ferritic nitrocarburizing===
Plasma-assisted ferritic nitrocarburizing is also known as '''ion nitriding''', '''plasma ion nitriding''' or '''glow-discharge nitriding'''. The process works to achieve the same result as the salt bath and gaseous process, except the reactivity of the media is not due to the temperature but to the gas ionized state.<ref>{{Harvnb|Pye|2003|p=71}}.</ref><ref>[http://www.asminternational.org/content/ASM/StoreFiles/06950G_Chapter_1.pdf An Introduction to Nitriding p. 9]</ref><ref>{{Citation|last = Pye|first = David|title = Steel Heat Treatment Metallurgy and Technologies|publisher = CRC Press|year = 2007| page = 493 |isbn = 978-0-8493-8452-3 | postscript =.}}</ref><ref>[http://ctklj.ctk.uni-lj.si/kovine/izvodi/mit046/mueller.pdf MINIMIZING WEAR THROUGH COMBINED THERMO CHEMICAL AND PLASMA ACTIVATED DIFFUSION AND COATING PROCESSES by Thomas Mueller, Andreas Gebeshuber, Roland Kullmer, Christoph Lugmair, Stefan Perlot, Monika Stoiber]</ref> In this technique intense electric fields are used to generate ionized molecules of the gas around the surface to diffuse the nitrogen and carbon into the workpiece. Such highly active gas with ionized molecules is called [[Plasma (physics)|plasma]], naming the technique. The gas used for plasma nitriding is usually pure nitrogen, since no spontaneous decomposition is needed (as is the case of gaseous ferritic nitrocarburizing with ammonia). Due to the relatively low temperature range ({{convert|420|°C|°F}} to {{convert|580|°C|°F}}) generally applied during plasma-assisted ferritic nitrocarburizing and gentle cooling in the furnace, the distortion of workpieces can be minimized. Stainless steel workpieces can be processed at moderate temperatures (like {{convert|420|°C|°F}}) without the formation of chromium nitride precipitates and hence maintaining their corrosion resistance properties.<ref name="Stainless">{{cite journal|doi=10.1016/S0257-8972(99)00084-5|last1=Larisch|first1=B|last2=Brusky|first2=U|last3=Spies|first3=HJ|year=1999|title=Plasma nitriding of stainless steels at low temperatures|pages=205|volume=116|journal=Surface and Coatings Technology}}</ref>
Plasma-assisted ferritic nitrocarburizing is also known as ion nitriding, plasma ion nitriding, or glow-discharge nitriding. The process works to achieve the same result as the salt bath and gaseous process, except the reactivity of the media is not due to the temperature but to the gas ionized state.<ref>{{Harvnb|Pye|2003|p=71}}.</ref><ref>{{cite web |url= http://www.asminternational.org/content/ASM/StoreFiles/06950G_Chapter_1.pdf |title=An Introduction to Nitriding p. 9 |access-date=2011-05-27 |archive-date=2011-12-15 |archive-url=https://web.archive.org/web/20111215235912/http://www.asminternational.org/content/ASM/StoreFiles/06950G_Chapter_1.pdf |url-status=dead }}</ref><ref>{{cite book|last=Pye |first=David |title=Steel Heat Treatment Metallurgy and Technologies |publisher=CRC Press |year=2007 |page=493 |isbn=978-0-8493-8452-3}}</ref><ref>{{cite journal |url= http://mit.imt.si/Revija/izvodi/mit046/mueller.pdf |title=Minimizing Wear Through Combined Thermo Chemical and Plasma Activated Diffusion and Coating Processes |first1=Thomas |last1=Mueller |first2=Andreas |last2=Gebeshuber |first3=Roland |last3=Kullmer |first4=Christoph |last4=Lugmair |first5=Stefan |last5=Perlot |first6=Monika |last6=Stoiber |date=2004 |journal=Materiali In Tehnologije |volume=38 |issue=6 |pages=353–357 |access-date=16 January 2023}}</ref> In this technique intense electric fields are used to generate ionized molecules of the gas around the surface to diffuse the nitrogen and carbon into the workpiece. Such highly active gas with ionized molecules is called [[Plasma (physics)|plasma]], naming the technique. The gas used for plasma nitriding is usually pure nitrogen since no spontaneous decomposition is needed (as is the case of gaseous ferritic nitrocarburizing with ammonia). Due to the relatively low-temperature range ({{convert|420|°C|°F}} to {{convert|580|°C|°F}}) generally applied during plasma-assisted ferritic nitrocarburizing and gentle cooling in the furnace, the distortion of workpieces can be minimized. Stainless steel workpieces can be processed at moderate temperatures (like {{convert|420|°C|°F}}) without the formation of chromium nitride precipitates and hence maintaining their corrosion resistance properties.<ref name="Stainless">{{cite journal|doi=10.1016/S0257-8972(99)00084-5|last1=Larisch|first1=B|last2=Brusky|first2=U|last3=Spies|first3=HJ |year=1999 |title=Plasma nitriding of stainless steels at low temperatures |pages=205–211 |volume=116 |journal=Surface and Coatings Technology}}</ref>

===Post-oxidation black oxide===
An additional step can be added to the nitrocarburizing process called post-oxidation. When properly performed, post-oxidation creates a layer of [[black oxide]] (Fe<sub>3</sub>O<sub>4</sub>), that greatly increases the corrosion resistance of the treated substrate while leaving an aesthetically attractive black color.<ref>{{cite web|last1=Holm|first1=Torsten|title=Furnace Atmospheres 3: Nitrading and Nitrocarburizing|url=https://www.ferronova.com/international/web/lg/fer/likelgfer.nsf/repositorybyalias/training_nitr/$file/Nitr3.pdf|website=ferronova.com|access-date=8 May 2017|archive-date=23 December 2015|archive-url=https://web.archive.org/web/20151223164111/https://www.ferronova.com/international/web/lg/fer/likelgfer.nsf/repositorybyalias/training_nitr/$file/Nitr3.pdf|url-status=dead}}</ref> Since the introduction of the [[Glock]] pistol in 1982, this type of nitrocarburizing with post-oxidation finish has become popular as a factory finish for military-style handguns.

This combination of nitrocarburizing and oxidizing is sometimes called "nitrox", but this word also has [[nitrox|another meaning]].<ref>For references, see in [[wikt:nitrox]].</ref>


==Uses==
==Uses==
These processes are most commonly used on low-carbon, low-alloy steels, however they are also used on medium and high-carbon steels. Common applications include [[spindle (tool)|spindles]], [[cam]]s, [[gear]]s, [[die (manufacturing)|dies]], [[hydraulic cylinder#Piston rod|hydraulic piston rods]], and [[powder metallurgy|powdered metal]] components.<ref>{{Harvnb|Pye|2003|p=222}}.</ref>
These processes are most commonly used on low-carbon, low-alloy steels. However, they are also used on medium and high-carbon steels. Typical applications include [[spindle (tool)|spindles]], [[Cam (mechanism)|cam]]s, [[gear]]s, [[die (manufacturing)|dies]], [[hydraulic cylinder#Piston rod|hydraulic piston rods]], and [[powder metallurgy|powdered metal]] components.<ref>{{Harvnb|Pye|2003|p=222}}.</ref>


One of the initial applications of the hardening process for mass-produced automobile engines was by [[Kaiser-Jeep]] for the [[crankshaft]] in the 1962 [[Jeep Tornado engine]].<ref>{{cite web |last1=Allen |first1=Jim |title=Classic Engine: Jeep's Tornado Straight-Six |url= https://www.cars.com/articles/classic-engine-jeeps-tornado-straight-six-454372/ |website=cars.com |date=30 October 2018 |access-date=16 January 2023}}</ref> This was one of many innovations in the OHC six-cylinder engine. The crankshaft was strengthened by Tufftriding in a unique salt bath for two hours at {{convert|1025|F|C}} that, according to Kaiser-Jeep, increased engine life by 50% and also made the journal surfaces hard enough to be compatible with heavy-duty tri-metal engine bearings.<ref>{{cite web|url= http://www.ifsja.org/tech/motors/tornado.html |title=Tornado 230 CI Engine Information / History |first=Ben |last=Page |work=The International Full Size Jeep Association |date=2006 |access-date=16 January 2023}}</ref>
⚫
[[Glock Ges.m.b.H.]], an [[Austria]]n firearms manufacturer, utilized the Tenifer process until 2010, to protect the barrels and slides of the [[pistols]] they manufacture. The finish on a [[Glock pistol]] is the third and final hardening process. It is {{convert|0.05|mm|in|abbr=on}} thick and produces a 64 [[Rockwell scale|Rockwell C hardness rating]] via a {{convert|500|C|F}} nitride bath. The final matte, non-glare finish meets or exceeds [[stainless steel]] specifications, is 85% more corrosion resistant than a hard [[Chrome plating|chrome]] finish, and is 99.9% salt-water corrosion resistant. After the Tenifer process, a black [[Parkerizing|Parkerized]] finish is applied and the slide is protected even if the finish were to wear off. In 2010 Glock switched to a gaseous ferritic nitrocarburizing process. Besides Glock several other pistol manufacturers, including [[Smith & Wesson]] and [[HS2000|Springfield Armory, Inc.]], also use ferritic nitrocarburizing for finishing parts like barrels and slides but they call it Melonite finish. [[Heckler & Koch]] use a nitrocarburizing process they refer to as Hostile Environment. Pistol manufacturer [[Caracal pistol|Caracal International L.L.C.]] uses ferritic nitrocarburizing for finishing parts such as barrels and slides with the plasma-based Plasox process.


[[File:Glock 17 (6825676904) без фона.jpg|thumb|A first-generation Glock 17 adopted in 1985 by the Norwegian Armed Forces under the P80 designation]]
[[Grandpower K100|Grandpower]], a Slovakian firearms producer, also uses a [[quench polish quench]] (QPQ) treatment to harden metal parts on its K100 pistols.<ref>[http://www.grandpower.eu/en/ Grandpower on Tenifer QPQ]</ref>

⚫
[[Glock Ges.m.b.H.]], an [[Austria]]n firearms manufacturer, utilized the Tenifer process until 2010, to protect the barrels and slides of the [[pistols]] they manufacture. The finish on a [[Glock pistol]] is the third and final hardening process. It is {{convert|0.05|mm|in|abbr=on}} thick and produces a 64 [[Rockwell scale|Rockwell C hardness rating]] via a {{convert|500|C|F}} nitride bath.<ref>{{cite book |last=Kasler |first=Peter Alan |pages=136–137 |title=Glock: The New Wave in Combat Handguns |year=1992 |publisher=Paladin Press |location=Boulder, CO |isbn=978-0-87364-649-9 | oclc=26280979}}</ref> The final matte, non-glare finish meets or exceeds [[stainless steel]] specifications, is 85% more corrosion resistant than a hard [[Chrome plating|chrome]] finish, and is 99.9% salt-water corrosion resistant.<ref>{{cite book | last=Kokalis | first=Peter |page=321 | title=Weapons Tests and Evaluations: The Best of Soldier of Fortune | year=2001 | publisher=Paladin Press |location=Boulder, CO | isbn=978-1-58160-122-0}}</ref> After the Tenifer process, a black [[Parkerizing|Parkerized]] finish is applied and the slide is protected even if the finish were to wear off. In 2010, Glock switched to a gaseous ferritic nitrocarburizing process.<ref name="MetalTreatments">{{cite web|url= http://firearmshistory.blogspot.com/2010/08/metal-treatments-ferritic.html |title=Firearms History, Technology & Development |access-date=25 December 2014 |date=2010-08-07}}</ref> Besides Glock other pistol and other firearms manufacturers, including [[Smith & Wesson]] and [[HS Produkt]], also use ferritic nitrocarburizing for finishing parts like barrels and slides, but they call it Melonite finish. [[Heckler & Koch]] use a nitrocarburizing process they refer to as Hostile Environment. Pistol manufacturer [[Caracal International]], headquartered in the United Arab Emirates, uses ferritic nitrocarburizing for finishing parts such as barrels and slides with the plasma-based post-oxidation process (PlasOx). [[Grand Power]], a Slovakian firearms producer, also uses a [[quench polish quench]] (QPQ) treatment to harden metal parts on its K100 pistols.<ref>{{cite web |url= http://www.grandpower.eu/en/ |title=Grandpower on Tenifer QPQ |access-date=2011-01-06 |archive-url= https://web.archive.org/web/20141026103206/http://www.grandpower.eu/en/ |archive-date=2014-10-26 }}</ref>


==References==
==References==
{{Reflist|2}}
{{Reflist|30em}}
{{reflist|group=Note}}

===Bibliography===
===Bibliography===
*{{Citation|last = Pye|first = David|title = Practical nitriding and ferritic nitrocarburizing|publisher = ASM International|year = 2003|url = https://books.google.com/books?id=5MJiR29ArTYC|isbn = 978-0-87170-791-8 | postscript =.}}
*{{Citation|last = Pye|first = David|title = Practical nitriding and ferritic nitrocarburizing|publisher = ASM International |year=2003 |url= https://books.google.com/books?id=5MJiR29ArTYC |isbn= 978-0-87170-791-8}}
<ref>{{cite web|last1=Pye|first1=David|title=About David Pye|url=http://pye-d.com/david-pye.php|website=Pye Metallurgical International Consulting|accessdate=10 January 2017}}</ref>
*{{cite web|last1=Pye|first1=David|title=About David Pye|url= http://pye-d.com/david-pye.php |website=pye-d.com |access-date=10 January 2017}}
<ref>{{cite web|last1=Pye|first1=David|title=Books By David Pye|url=http://pye-d.com/heat-treatment-books-by-david-pye.php|website=Pye Metallurgical International Consulting|accessdate=10 January 2017}}</ref>
*{{cite web|last1=Pye|first1=David|title=Books By David Pye|url= http://pye-d.com/heat-treatment-books-by-david-pye.php |website=pye-d.com |access-date=10 January 2017}}
⚫
*{{Citation|url=https://books.google.com/books?id=Lt7WBiILHpYC&pg=PA115 |page=115 |title=Surface engineering for corrosion and wear resistance |first=Joseph R. |last=Davis |publisher=ASM International |year=2001 |isbn=0-87170-700-4}}


==External links==
==External links==
*[http://www.durferrit.de/media/pdf/Tenifer_QPQ_eng.pdf Tufftride-/QPQ-process: technical information]
*[http://www.durferrit.de/media/pdf/Tenifer_QPQ_eng.pdf Tufftride-/QPQ-process: technical information]
*[http://www.keighleylabs.co.uk/heat-treatment-html/tufftride-ferritic-nitrocarburizing/ : What is Tufftride?]
*[http://www.keighleylabs.co.uk/heat-treatment-html/tufftride-ferritic-nitrocarburizing/ : What is Tufftride?]

⚫
*{{Citation|url=https://books.google.com/books?id=Lt7WBiILHpYC&pg=PA115&lpg=PA115|page=115|title=Surface engineering for corrosion and wear resistance|author=Joseph R. Davis|publisher=ASM International|year=2001|isbn=0-87170-700-4}}
{{Iron and steel production}}


{{DEFAULTSORT:Ferritic Nitrocarburizing}}
{{DEFAULTSORT:Ferritic Nitrocarburizing}}

Latest revision as of 17:50, 19 August 2024

Not to be confused with Carbonitriding.

Ferritic nitrocarburizing or FNC, also known by the proprietary names "Tenifer", "Tufftride", Melonite, and "Arcor",[Note 1][1] is a range of proprietary case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures during a salt bath. Other methods of ferritic nitrocarburizing include gaseous processes such as Nitrotec and ion (plasma) ones. The processing temperature ranges from 525 °C (977 °F) to 625 °C (1,157 °F), but usually occurs at 565 °C (1,049 °F). Steel and other ferrous alloys remain in the ferritic phase region at this temperature. This allows for better control of the dimensional stability that would not be present in case hardening processes that occur when the alloy is transitioned into the austenitic phase.[2] There are four main classes of ferritic nitrocarburizing: gaseous, salt bath, ion or plasma, and fluidized-bed.[3]

The process improves three main surface integrity aspects: scuffing resistance, fatigue properties, and corrosion resistance. It has the 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.[4]

History

[edit]

The first ferritic nitrocarburizing methods were done at low temperatures, around 550 °C (1,022 °F), 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[5][6] 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.[7]

Because of the cleaning issues, Lucas Industries began experimenting with gaseous forms of ferritic nitrocarburizing in the late 1950s. The company applied for a patent in 1961. It produced a similar surface finish as the Sulfinuz process, except for the formation of sulfides. The atmosphere consists of ammonia, hydrocarbon gases, and a small amount of other carbon-containing gases.[8]

This innovation spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents.[9] Their process is 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.[10]

Processes

[edit]

Despite the naming, the process is a modified form of nitriding and not carburizing. The shared attribute of this class of this process is the introduction of nitrogen and carbon in the ferritic state of the material. The processes are divided into four main classes: gaseous, salt bath, ion or plasma, or fluidized-bed. The trade name and patented processes may vary slightly from the general description, but they are all a form of ferritic nitrocarburizing.[11]

Salt bath ferritic nitrocarburizing

[edit]

Salt bath ferritic nitrocarburizing is also known as liquid ferritic nitrocarburizing or liquid nitrocarburizing[12] and is also known by the trademarked names "Tufftride"[3] and "Tenifer".[13]

The simplest form of this process is encompassed by the trademarked "Melonite" process, also known as "Meli 1". It is most commonly used on steels, sintered irons, and cast irons to lower friction and improve wear and corrosion resistance.[14][15]

The process uses a salt bath of alkali cyanate. This is contained in a steel pot that has an aeration system. The cyanate thermally reacts with the surface of the workpiece to form an alkali carbonate. The bath is then treated to convert the carbonate back to a cyanate. The surface formed from the reaction has a compound layer and a diffusion layer. The compound layer consists of iron, nitrogen, and oxygen is abrasion resistant and is stable at elevated temperatures. The diffusion layer contains nitrides and carbides. The surface hardness ranges from 800 to 1500 HV depending on the steel grade. This also inversely affects the depth of the case; i.e., a high carbon steel will form a hard, but shallow case.[14]

A similar process is the trademarked "Nu-Tride" process, also known incorrectly as the "Kolene" process (which is the company's name), includes a preheat and an intermediate quench cycle. The intermediate quench is an oxidizing salt bath at 400 °C (752 °F). This quench is held for 5 to 20 minutes before the final quenching to room temperature. This is done to minimize distortion and to destroy any lingering cyanates or cyanides left on the workpiece.[16]

Other trademarked processes are "Sursulf" and "Tenoplus". Sursulf has a sulfur compound in the salt bath to create surface sulfides creating porosity in the workpiece surface. This porosity is used to contain lubrication. Tenoplus is a two-stage high-temperature process. The first stage occurs at 625 °C (1,157 °F), while the second stage occurs at 580 °C (1,076 °F).[17]

Gaseous ferritic nitrocarburizing

[edit]

Gaseous ferritic nitrocarburizing is also known as controlled nitrocarburizing, soft nitriding, and vacuum nitrocarburizing or by the tradenames "UltraOx",[18] "Nitrotec", "Nitemper", "Deganit", "Triniding", "Corr-I-Dur", "Nitroc", "Nitreg-C",[19] "Nitrowear", and "Nitroneg".[3][20] The process works to achieve the same result as the salt bath process, except gaseous mixtures are used to diffuse the nitrogen and carbon into the workpiece.[21]

The parts are first cleaned, usually with a vapor degreasing process, and then nitrocarburized around 570 °C (1,058 °F), with a processing time that ranges from one to four hours. The actual gas mixtures are proprietary, but they usually contain ammonia and an endothermic gas.[21]

In comparison to a standard nitriding process, ferritic nitrocarburizing or FNC in a vacuum furnace takes less time to achieve case depth requirements - mainly in part due to the addition of carbon to achieve faster diffusion.[22]

Plasma-assisted ferritic nitrocarburizing

[edit]

Plasma-assisted ferritic nitrocarburizing is also known as ion nitriding, plasma ion nitriding, or glow-discharge nitriding. The process works to achieve the same result as the salt bath and gaseous process, except the reactivity of the media is not due to the temperature but to the gas ionized state.[23][24][25][26] In this technique intense electric fields are used to generate ionized molecules of the gas around the surface to diffuse the nitrogen and carbon into the workpiece. Such highly active gas with ionized molecules is called plasma, naming the technique. The gas used for plasma nitriding is usually pure nitrogen since no spontaneous decomposition is needed (as is the case of gaseous ferritic nitrocarburizing with ammonia). Due to the relatively low-temperature range (420 °C (788 °F) to 580 °C (1,076 °F)) generally applied during plasma-assisted ferritic nitrocarburizing and gentle cooling in the furnace, the distortion of workpieces can be minimized. Stainless steel workpieces can be processed at moderate temperatures (like 420 °C (788 °F)) without the formation of chromium nitride precipitates and hence maintaining their corrosion resistance properties.[27]

Post-oxidation black oxide

[edit]

An additional step can be added to the nitrocarburizing process called post-oxidation. When properly performed, post-oxidation creates a layer of black oxide (Fe3O4), that greatly increases the corrosion resistance of the treated substrate while leaving an aesthetically attractive black color.[28] Since the introduction of the Glock pistol in 1982, this type of nitrocarburizing with post-oxidation finish has become popular as a factory finish for military-style handguns.

This combination of nitrocarburizing and oxidizing is sometimes called "nitrox", but this word also has another meaning.[29]

Uses

[edit]

These processes are most commonly used on low-carbon, low-alloy steels. However, they are also used on medium and high-carbon steels. Typical applications include spindles, cams, gears, dies, hydraulic piston rods, and powdered metal components.[30]

One of the initial applications of the hardening process for mass-produced automobile engines was by Kaiser-Jeep for the crankshaft in the 1962 Jeep Tornado engine.[31] This was one of many innovations in the OHC six-cylinder engine. The crankshaft was strengthened by Tufftriding in a unique salt bath for two hours at 1,025 °F (552 °C) that, according to Kaiser-Jeep, increased engine life by 50% and also made the journal surfaces hard enough to be compatible with heavy-duty tri-metal engine bearings.[32]

A first-generation Glock 17 adopted in 1985 by the Norwegian Armed Forces under the P80 designation

Glock Ges.m.b.H., an Austrian firearms manufacturer, utilized the Tenifer process until 2010, to protect the barrels and slides of the pistols they manufacture. The finish on a Glock pistol is the third and final hardening process. It is 0.05 mm (0.0020 in) thick and produces a 64 Rockwell C hardness rating via a 500 °C (932 °F) nitride bath.[33] The final matte, non-glare finish meets or exceeds stainless steel specifications, is 85% more corrosion resistant than a hard chrome finish, and is 99.9% salt-water corrosion resistant.[34] After the Tenifer process, a black Parkerized finish is applied and the slide is protected even if the finish were to wear off. In 2010, Glock switched to a gaseous ferritic nitrocarburizing process.[35] Besides Glock other pistol and other firearms manufacturers, including Smith & Wesson and HS Produkt, also use ferritic nitrocarburizing for finishing parts like barrels and slides, but they call it Melonite finish. Heckler & Koch use a nitrocarburizing process they refer to as Hostile Environment. Pistol manufacturer Caracal International, headquartered in the United Arab Emirates, uses ferritic nitrocarburizing for finishing parts such as barrels and slides with the plasma-based post-oxidation process (PlasOx). Grand Power, a Slovakian firearms producer, also uses a quench polish quench (QPQ) treatment to harden metal parts on its K100 pistols.[36]

References

[edit]
  1. ^ Totten, George E. (28 September 2006). Steel Heat Treatment: Metallurgy and Technologies. CRC. p. 530. ISBN 978-0-8493-8452-3.
  2. ^ Pye 2003, p. 193.
  3. ^ a b c Pye 2003, p. 202.
  4. ^ Pye 2003, pp. 193–194.
  5. ^ Archived at Ghostarchive and the Wayback Machine: ICI End of Process – Castner Process at Cassel Works. Transfilm UK – via YouTube.
  6. ^ The 'Cassel' 'Sulfinuz' Process. Imperial Chemical Industries. 1954.
  7. ^ Pye 2003, p. 195.
  8. ^ Pye 2003, pp. 195–196.
  9. ^ Velstrop, Hans (22 February 2015). "To find the way in the nomenclature jungle of nitrogen diffusion".
  10. ^ Pye 2003, pp. 196–197.
  11. ^ Pye 2003, pp. 201–202.
  12. ^ Easterday, James R. "Liquid Ferritic Nitrocarburizing" (PDF). domino-69.prominic.net. Archived from the original (PDF) on 14 August 2011. Retrieved 19 August 2024..
  13. ^ History of the company, archived from the original on 2009-08-26, retrieved 2009-09-29.
  14. ^ a b Pye 2003, p. 203.
  15. ^ Melonite Processing, retrieved 2009-09-17.
  16. ^ Pye 2003, pp. 208–210.
  17. ^ Pye 2003, p. 217.
  18. ^ "UltraOx". ahtcorp.com. Retrieved 16 January 2023.
  19. ^ "nitrocarburizing Nitreg-C". nitrex.com/en/. Retrieved 19 August 2024.
  20. ^ Pye 2003, p. 220.
  21. ^ a b Pye 2003, p. 219.
  22. ^ "Ferritic Nitrocarburizing (FNC) - Overview". ecm-usa.com. Retrieved 19 August 2024.
  23. ^ Pye 2003, p. 71.
  24. ^ "An Introduction to Nitriding p. 9" (PDF). Archived from the original (PDF) on 2011-12-15. Retrieved 2011-05-27.
  25. ^ Pye, David (2007). Steel Heat Treatment Metallurgy and Technologies. CRC Press. p. 493. ISBN 978-0-8493-8452-3.
  26. ^ Mueller, Thomas; Gebeshuber, Andreas; Kullmer, Roland; Lugmair, Christoph; Perlot, Stefan; Stoiber, Monika (2004). "Minimizing Wear Through Combined Thermo Chemical and Plasma Activated Diffusion and Coating Processes" (PDF). Materiali In Tehnologije. 38 (6): 353–357. Retrieved 16 January 2023.
  27. ^ Larisch, B; Brusky, U; Spies, HJ (1999). "Plasma nitriding of stainless steels at low temperatures". Surface and Coatings Technology. 116: 205–211. doi:10.1016/S0257-8972(99)00084-5.
  28. ^ Holm, Torsten. "Furnace Atmospheres 3: Nitrading and Nitrocarburizing" (PDF). ferronova.com. Archived from the original (PDF) on 23 December 2015. Retrieved 8 May 2017.
  29. ^ For references, see in wikt:nitrox.
  30. ^ Pye 2003, p. 222.
  31. ^ Allen, Jim (30 October 2018). "Classic Engine: Jeep's Tornado Straight-Six". cars.com. Retrieved 16 January 2023.
  32. ^ Page, Ben (2006). "Tornado 230 CI Engine Information / History". The International Full Size Jeep Association. Retrieved 16 January 2023.
  33. ^ Kasler, Peter Alan (1992). Glock: The New Wave in Combat Handguns. Boulder, CO: Paladin Press. pp. 136–137. ISBN 978-0-87364-649-9. OCLC 26280979.
  34. ^ Kokalis, Peter (2001). Weapons Tests and Evaluations: The Best of Soldier of Fortune. Boulder, CO: Paladin Press. p. 321. ISBN 978-1-58160-122-0.
  35. ^ "Firearms History, Technology & Development". 2010-08-07. Retrieved 25 December 2014.
  36. ^ "Grandpower on Tenifer QPQ". Archived from the original on 2014-10-26. Retrieved 2011-01-06.
  1. ^ Other trade names include Tuffride/ Tuffrider, QPQ, Sulfinuz, Sursulf, Meli 1, and Nitride, among others

Bibliography

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[edit]
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