SBN/QPQ SM (salt bath nitriding), or Quench-Polish-Quench, is particularly important to oil field equipment and other manufacturers whose parts are subject to high levels of wear, friction, or erosion. 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. It is used to improve wear resistance and fatique strength of cast iron, sintered iron and steel. The shared attributes of this class of this process is the introduction of nitrogen and carbon in the ferritic state of the material. It has the added advantage of inducing little shape distortion during the hardening process. An added benefit of the process is minimal distortion due to short process cycle within the ferrite phase. The compound layer consists of iron, nitrogen, and oxygen, is abrasion resistant, and stable at elevated temperatures. Liquid Salt Bath Ferritic Nitrocarburizing Non-Cyanide Bath(STABILIZED Jul 2019) AMS2753D This specification covers the requirements for an epsilon-iron nitride case on ferrous parts produced by immersion in a low-temperature, agitated, fused salt bath. [30] Besides Glock several other pistol manufacturers, including Smith & Wesson and Springfield Armory, Inc., also use ferritic nitrocarburizing for finishing parts like barrels and slides but they call it Melonite finish. a high carbon steel will form a hard, but shallow case. Nitrocarburizing and carbonitriding sound somewhat similar and they perform similar functions: to make a workpiece surface harder by imparting carbon, nitrogen or both to its surface. It is used as a post-nitride ‘quench bath.’ This neutralizes any potential toxic compounds which may have formed as a result of nitriding bath reactions reacting with any nitriding salt residues adhering to the components or fixtures. The processing temperature ranges from 525 °C (977 °F) to 625 °C (1,157 °F), but usually occurs at 565 °C (1,049 °F). Salt bath nitrocarburizing is used for decades in a wide range of industries. It produced a similar surface finish as the Sulfinuz process with the exception of the formation of sulfides. [3][19] 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. The processes are broken up into four main classes: gaseous, salt bath, ion or plasma, or fluidized-bed. [7], Because of the cleaning issues the Joseph Lucas Limited company began experimenting with gaseous forms of ferritic nitrocarburizing in the late 1950s. With the introduction of nitrogen in the diffused zone fatigue properties are enhanced. The intermediate quench is an oxidizing salt bath at 400 °C (752 °F). Salt Bath Nitriding/Nitrocarburizing was originally created as an alternative to gas nitriding that would produce a more uniform case through surface contact between the substrate and liquid salt. 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. A salt bath uses a liquid salt solution that is usually heated between 750 degrees Fahrenheit and 1050 degrees Fahrenheit. Post-oxidation after nitriding combined with polishing produces coatings with exceptional appearance (black color) and high corrosion resistance (greater than electrolytic chrome plating). It is mandatory that the salt bath chemistry is checked at the commencement of each shift and the appropriate additions of salt are added to return the bath to its operational strength. At this temperature steels and other ferrous alloys remain in the ferritic phase region. Salt Bath Nitriding/Nitrocarburizing was originally created as an alternative to gas nitriding that would produce a more uniform case through surface contact between the substrate and liquid salt. The bath is then treated to convert the carbonate back to a cyanate. It is a range of proprietary case hardening processes that diffuse nitrogen and carbon into ferrous metals at sub-critical temperatures during a salt bath. Sursulf has a sulfur compound in the salt bath to create surface sulfides which creates porosity in the workpiece surface. 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. [20], The parts are first cleaned, usually with a vapor degreasing process, and then nitrocarburized around 570 °C (1,058 °F), with a process time that ranges from one to four hours. These processes are most commonly used on low-carbon, low-alloy steels, however they are also used on medium and high-carbon steels. [17], 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 and Nitrowear, Nitroneg. The processes are broken up into four main classes: gaseous, salt bath, ion or plasma, or fluidized-bed. Despite the naming the process is a modified form of nitriding and not carburizing. [16], Other trademarked processes are Sursulf and Tenoplus. [29] After the Tenifer process, a black Parkerized finish is applied and the slide is protected even if the finish were to wear off. Nitrocarburizing / Salt Bath Nitriding Ionic liquids offer a significant improvement in wear protection, sliding properties and fatigue strength on all kind of ferrous materials. In combination with oxidation bath it improves corrosion resistance and reduces surface roughness. The finish on a Glock pistol is the third and final hardening process. It is a thermochemical diffusion process whereby nitrogen-bearing salts generate a controlled release of … [28] 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. 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 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). The actual gas mixtures are proprietary, but they usually contain ammonia and an endothermic gas. The next step is a mechanical polish of the nitride layer, thus restoring the original surface finish. Grandpower, a Slovakian firearms producer, also uses a quench polish quench (QPQ) treatment to harden metal parts on its K100 pistols. uses ferritic nitrocarburizing for finishing parts such as barrels and slides with the plasma-based post oxidation process (PlasOx). [2] There are four main classes of ferritic nitrocarburizing: gaseous, salt bath, ion or plasma, and fluidized-bed. Typically, this process involves either a salt bath nitriding or nitrocarburizing to properly treat a barrel. [26] Since the introduction of the Glock pistol in 1982, this type of nitrocarburizing with postoxidation finish has become popular as a factory finish for military style handguns. The process is carried out at 750-1050°F, making it faster than gas nitriding. This process is preferred for improving tribological and surface properties of ferrous components in addition to improving fatigue strength. The Nitrocarburizing process step is conducted in the MEL 1 / TF 1 bath at 896-1166°F, the standard temperature is usually 1076°F. The atmosphere consisted of ammonia, hydrocarbon gases, and a small amount of other carbon-containing gases. To ensure part quality, our salt baths are continuously monitored, with chemistry adjustments made when necessary. What is the basic principle of Liquid Nitriding? Parts are typically core treated and finished machined prior to nitriding, with some allowance being made for a slight amount of growth. Unlike nitriding methods using a salt bath, gas nitriding is a more flexible process with easier disposal of the nitriding agent. The temperature used is typical of all nitrocarburizing processes: 550 to 570 °C. The first stage occurs at 625 °C (1,157 °F), while the second stage occurs at 580 °C (1,076 °F). Modern salt-bath plant Nitrocarburizing offers an alternative to complicated coating processes and enables manufacturers to replace expensive materials with less costly ones. (a) salt bath (liquid) nitriding, where the source of nitrogen (and also carbon) is molten salt. [11], 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. Salt bath nitriding is a thermochemical process in which nitrogen and carbon are diffused simultaneously into the surface of the material. The company applied for a patent by 1961. Heckler & Koch use a nitrocarburizing process they refer to as Hostile Environment. It is a thermochemical diffusion process whereby nitrogen-bearing salts generate a controlled release of nitrogen at the interface of a ferrous part. The process is gaining a great deal of popularity in North America due to legislation on process effluents, European engineering specifications and a growing awareness of the process repeatability and metallurgical consistency due to computer control (Fig. The first company to successfully commercialize the process was the Imperial Chemical Industries in Great Britain. The primary objective of ferritic nitrocarburising treatment is to improve the anti-scuffing characteristics of components. [8], This spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents. Following this the ion nitriding process was invented in the early 1980s. Salt baths are not used by Nitrex due to that method’s environmental dangers and our concern for personal safety of the operators. This porosity is used to contain lubrication. In combination with oxidation bath it improves corrosion resistance and reduces surface roughness. [21][22][23][24] 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. Salt-bath nitrocarburized steel, sintered iron and cast iron parts have very good wear, corrosion and fatigue resistance, as well as enhanced sliding proper-ties. The trade name and patented processes may vary slightly from the general description, but they are all a form of ferritic nitrocarburizing. Houston Unlimited, Inc. offers a salt bath nitriding process, also referred to as liquid salt bath ferritic nitrocarburizing. [31], Plasma-assisted ferritic nitrocarburizing, Other trade names include Tuffride/ Tuffrider, QPQ, Sulfinuz, Sursulf, Meli 1, and Nitride, among others, https://www.youtube.com/watch?v=yt2DU-22qus, "To find the way in the nomenclature jungle of nitrogen diffusion", https://www.ahtcorp.com/services/nitriding-and-nitrocarburizing/ultraox/, 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, "Furnace Atmospheres 3: Nitrading and Nitrocarburizing", "Firearms History, Technology & Development", Tufftride-/QPQ-process: technical information, https://en.wikipedia.org/w/index.php?title=Ferritic_nitrocarburizing&oldid=995211950, Creative Commons Attribution-ShareAlike License, This page was last edited on 19 December 2020, at 20:51. Liquid Nitriding (LN) is a common term for a diffusion process that is actually liquid nitrocarburizing; a thermo-chemical reaction whereby nitrogen, primarily, and some carbon are diffused into the surface of iron-based materials. When steel parts are placed into a preheated liquid salt, there is sufficient energy localized near the surface due to differences in chemical potential that then allows nitrogen and carbon species to diffuse from the salt into the steel substrate. Besides, the process has few advantages, quick heating of the workpiece being the only one worth mentioning. 2. Due to the main process characteristics like Treatment Cycle Melonite-QPQ - SHOW - - HIDE - This complete process sequence is shown above and is in fact the QPQ®-process. During the process, a two-part surface layer is formed, an outer iron nitride layer with a nitrogen diffusion layer below it. [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. [9] Their process is the widely known as the Tufftride or Tenifer process. When properly performed, postoxidation creates a layer of black oxide (Fe3O4), that greatly increases the corrosion resistance of the treated substrate while leaving an aesthetically attractive black color. [14][15], The process uses a salt bath of alkali cyanate. 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. Ferritic Nitrocarburizing is the thermochemical process that simultaneously diffuses nitrogen and carbon into the surface of ferrous metals. Salt Bath Nitriding/Nitrocarburizing is well known under various trade names, including ARCOR®, TENIFER®, TUFFTRIDE®, MELONITE®, and QPQ®. [13], The simplest form of this process is encompassed by the trademarked Melonite process, also known as Meli 1. The compound layer exhibits significant improvement in adhesive wear resistance. ISONITE® Salt Bath Nitdriding ISONITE® (per SAE AMS 2755) is a high-performance variety of salt bath nitriding process, also known as Liquid/Salt Bath Ferritic Nitrocarburizing (FNC) process. The diffusion layer contains nitrides and carbides. Lower temperature cycles produce an S-Phase/Expanded Austenite case in stainless steels. The surface hardness ranges from 800 to 1500 HV depending on the steel grade. It is also known as Liquid/Salt Bath Ferritic Nitrocarburizing (FNC) process. This also inversely affects the depth of the case; i.e. ISONITE® QPQ (per SAE AMS 2753) is a high-performance variety of salt bath nitrocarburizing process. 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