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Ferritic nitrocarburizing

October 27, 2023

Not to be confused with Carbonitriding.

Ferritic nitrocarburizing or FNC, also known by the proprietary names Tenifer, Tufftride and Melonite as well as 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 ferric 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). At this temperature steels and other ferrous alloys remain in the ferritic phase region. 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 is used to improve three main surface integrity aspects including scuffing resistance, 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 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 with the exception of the formation of sulfides. The atmosphere consisted of ammonia, hydrocarbon gases, and a small amount of other carbon-containing gases.[8]

This spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents.[9] 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.[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 actually the company's name), which 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 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 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]

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.[22][23][24][25] 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.[26]

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.[27] 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.[28]

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. Common applications include spindles, cams, gears, dies, hydraulic piston rods, and powdered metal components.[29]

One of the initial applications of the hardening process for mass-produced automobile engines was by Kaiser-Jeep for the crankshaft in the new Jeep Tornado engine.[30] This was one of many innovations in the OHC six-cylinder engine. The crankshaft was strengthened by Tufftriding in a special salt bath for two hours at 1,025 °F (552 °C) which, according to Kaiser-Jeep, increased, said Willys, engine life by 50% and also made the journal surfaces hard enough to be compatible with heavy duty tri-metal engine bearings.[31]

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.[32] 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.[33] 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.[34] 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.[35]

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 : 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., (PDF), archived from the original (PDF) on 2011-07-24, retrieved 2009-09-17.
  13. ^ , 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". www.nitrex.com/en/. Retrieved 2023-02-22.
  20. ^ Pye 2003, p. 220.
  21. ^ a b Pye 2003, p. 219.
  22. ^ Pye 2003, p. 71.
  23. ^ An Introduction to Nitriding p. 9
  24. ^ Pye, David (2007), Steel Heat Treatment Metallurgy and Technologies, CRC Press, p. 493, ISBN 978-0-8493-8452-3.
  25. ^ 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.
  26. ^ 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.
  27. ^ Holm, Torsten. "Furnace Atmospheres 3: Nitrading and Nitrocarburizing" (PDF). ferronova.com. Retrieved 8 May 2017.
  28. ^ For references, see in wikt:nitrox.
  29. ^ Pye 2003, p. 222.
  30. ^ Allen, Jim (30 October 2018). "Classic Engine: Jeep's Tornado Straight-Six". cars.com. Retrieved 16 January 2023.
  31. ^ Page, Ben (2006). "Tornado 230 CI Engine Information / History". The International Full Size Jeep Association. Retrieved 16 January 2023.
  32. ^ 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.
  33. ^ 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.
  34. ^ "Firearms History, Technology & Development". 2010-08-07. Retrieved 25 December 2014.
  35. ^ . 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 Edit

  • Pye, David (2003), Practical nitriding and ferritic nitrocarburizing, ASM International, ISBN 978-0-87170-791-8
  • Pye, David. "About David Pye". pye-d.com. Retrieved 10 January 2017.
  • Pye, David. "Books By David Pye". pye-d.com. Retrieved 10 January 2017.
  • Davis, Joseph R. (2001), Surface engineering for corrosion and wear resistance, ASM International, p. 115, ISBN 0-87170-700-4

External links Edit

  • Tufftride-/QPQ-process: technical information
  • : What is Tufftride?

October 27, 2023
ferritic, nitrocarburizing, confused, with, carbonitriding, also, known, proprietary, names, tenifer, tufftride, melonite, well, arcor, note, range, proprietary, case, hardening, processes, that, diffuse, nitrogen, carbon, into, ferrous, metals, critical, temp. Not to be confused with Carbonitriding Ferritic nitrocarburizing or FNC also known by the proprietary names Tenifer Tufftride and Melonite as well as 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 ferric 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 At this temperature steels and other ferrous alloys remain in the ferritic phase region 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 is used to improve three main surface integrity aspects including scuffing resistance 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 transitions in steel 4 Contents 1 History 2 Processes 2 1 Salt bath ferritic nitrocarburizing 2 2 Gaseous ferritic nitrocarburizing 2 3 Plasma assisted ferritic nitrocarburizing 2 4 Post oxidation black oxide 3 Uses 4 References 4 1 Bibliography 5 External linksHistory EditThe 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 with the exception of the formation of sulfides The atmosphere consisted of ammonia hydrocarbon gases and a small amount of other carbon containing gases 8 This spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents 9 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 10 Processes EditDespite 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 actually the company s name which 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 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 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 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 22 23 24 25 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 26 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 27 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 28 Uses EditThese 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 spindles cams gears dies hydraulic piston rods and powdered metal components 29 One of the initial applications of the hardening process for mass produced automobile engines was by Kaiser Jeep for the crankshaft in the new Jeep Tornado engine 30 This was one of many innovations in the OHC six cylinder engine The crankshaft was strengthened by Tufftriding in a special salt bath for two hours at 1 025 F 552 C which according to Kaiser Jeep increased said Willys engine life by 50 and also made the journal surfaces hard enough to be compatible with heavy duty tri metal engine bearings 31 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 32 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 33 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 34 Besides Glock other pistol and other firearms manufacturers including Smith amp Wesson and HS Produkt also use ferritic nitrocarburizing for finishing parts like barrels and slides but they call it Melonite finish Heckler amp 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 35 References Edit Totten George E 28 September 2006 Steel Heat Treatment Metallurgy and Technologies CRC p 530 ISBN 978 0 8493 8452 3 Pye 2003 p 193 a b c Pye 2003 p 202 Pye 2003 pp 193 194 Archived at Ghostarchive and the Wayback Machine ICI End of Process Castner Process at Cassel Works Transfilm UK via YouTube The Cassel Sulfinuz Process Imperial Chemical Industries 1954 Pye 2003 p 195 Pye 2003 pp 195 196 Velstrop Hans 22 February 2015 To find the way in the nomenclature jungle of nitrogen diffusion Pye 2003 pp 196 197 Pye 2003 pp 201 202 Easterday James R Liquid Ferritic Nitrocarburizing PDF archived from the original PDF on 2011 07 24 retrieved 2009 09 17 History of the company archived from the original on 2009 08 26 retrieved 2009 09 29 a b Pye 2003 p 203 Melonite Processing retrieved 2009 09 17 Pye 2003 pp 208 210 Pye 2003 p 217 UltraOx ahtcorp com Retrieved 16 January 2023 NITROCARBURIZING NITREG C Nitrex www nitrex com en Retrieved 2023 02 22 Pye 2003 p 220 a b Pye 2003 p 219 Pye 2003 p 71 An Introduction to Nitriding p 9 Pye David 2007 Steel Heat Treatment Metallurgy and Technologies CRC Press p 493 ISBN 978 0 8493 8452 3 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 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 Holm Torsten Furnace Atmospheres 3 Nitrading and Nitrocarburizing PDF ferronova com Retrieved 8 May 2017 For references see in wikt nitrox Pye 2003 p 222 Allen Jim 30 October 2018 Classic Engine Jeep s Tornado Straight Six cars com Retrieved 16 January 2023 Page Ben 2006 Tornado 230 CI Engine Information History The International Full Size Jeep Association Retrieved 16 January 2023 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 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 Firearms History Technology amp Development 2010 08 07 Retrieved 25 December 2014 Grandpower on Tenifer QPQ Archived from the original on 2014 10 26 Retrieved 2011 01 06 Other trade names include Tuffride Tuffrider QPQ Sulfinuz Sursulf Meli 1 and Nitride among others Bibliography Edit Pye David 2003 Practical nitriding and ferritic nitrocarburizing ASM International ISBN 978 0 87170 791 8 Pye David About David Pye pye d com Retrieved 10 January 2017 Pye David Books By David Pye pye d com Retrieved 10 January 2017 Davis Joseph R 2001 Surface engineering for corrosion and wear resistance ASM International p 115 ISBN 0 87170 700 4External links EditTufftride QPQ process technical information What is Tufftride Retrieved from https en wikipedia org w index php title Ferritic nitrocarburizing amp oldid 1179311286, wikipedia, wiki, book, books, library,

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