The composition includes alkali metal cyanate and alkali metal carbonate, wherein the cyanate ion is present in a weight percentage of greater than 45% and less than 55.2%. The composition is fused and maintained between about 750° F. and about 950° F. depending upon the type of stainless steel to be treated. Again, when multiple samples were tested, the maximum time is shown. The processes are named after the medium used to donate. Even temperatures between 815° F. and 850° F. will provide a deeper case while somewhat diminishing the corrosion resistance. These are unique & reliable heat treatment solution for automobile industries as well as machine tools manufacturers, irrespective of … Thus, nitriding is similar to carburizing in that surface composition is altered, but different in that nitrogen is added into ferrite instead of austenite. Salt baths are not used by Nitrex due to that method’s environmental dangers and our concern for personal safety of the operators. 4 comprises curves showing the depth of the case formed at various times and temperatures on the specimens of the 416 grade stainless steel. Nitriding((Ferritic(Nitrocarburizing)(–(fundamentals,(modeling(and(process(optimization(Report!No.!13,01!! Liquid nitriding uses a cyanide salt mixture in a bath. 5 is a curve that shows the influence of the salt bath nitriding temperature on the core hardness of the pre-hardened and tempered 416 grade stainless steel. 1 is a bar graph of the corrosion resistance of various samples of 304 stainless steel treated at various temperatures; FIG. This result may be acceptable. Gas nitriding is not restricted but normally a practically reasonable time of 90- 98 hours is not exceeded. Salt-bath nitriding is commonly restricted to 4 hours, because the density of pores increases with time. Though less than half of … Specifically, the object of the tests with respect to the 304 stainless steel, which is characteristic of the austenitic grade, was to determine the effect of salt bath nitriding at various temperatures and times on the corrosion resistance of the material and the depth of CL or hard layer formed. The samples were immersed in salt bath for ten different times (1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h ) at 580 °C, salt bath nitriding treatments applied to 42CrMo4 steel are given in Fig. For salt bath nitriding, mainly cyanides (sodium cyanide or potassium cyanide) and cyanates (sodium cyanate or potassium cyanate) are used. Nitriding is a popular case hardening technique renowned for the qualities it delivers at relatively low process temperatures. actual nitriding environment. Thus, when greater-depth than that can be obtainable with salt-bath nitriding is required, gas-nitriding … Manufacturers and Suppliers of Nitriding Chemicals, Nitriding Salt, Heat Treatment Chemicals / Salts, Mumbai, India Nitriding in salt baths was replaced by gas nitriding for virtually all the parts, and only some items, like exhaust valves, were still treated in salt baths but at subsidiary plants. Tools and small components are often liquid-nitrided. USA;REEL/FRAME:026719/0538, Low temperature nitrocarburizing salt and method of use, Method for processing parts for kitchen tools, Roller chain, e.g. Besides, the process has few advantages, quick heating of the work piece being the only one worth mentioning. Nitriding of Interstitial Free Steel in Potassium–Nitrate Salt Bath Yin Zhong SHEN, 1) Kyu Hwan OH 1) and Dong Nyung LEE 1) School of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 151-744, Korea. As the temperatures increase above 815° F., the ‘S’ phase begins to transform into nitride(s) and, at 950° F., it is completely transformed into nitrides. The metal composite comprises a stainless steel interior component and a deposited nitrided metal exterior layer, wherein the nitrided exterior layer has lower electric contact resistance and greater corrosion resistance than the stainless steel interior component. FIG. The test was terminated after 10% area was corroded or 1032 hours, whichever came first. With our more than 15 years of rich experience, we have carved a favorable niche for ourselves in this competitive market by offering qualitative Liquid Nitriding Salt. It seemed that the high toxicity of the initially used compositions for soft nitriding (Tufftride or Tenifer) should have eliminated salt baths from the industry. case depth) based on the input of the process parameters of KOLENE CORPORATION, MICHIGAN, Free format text: With additional increase in temperature, i.e. Five different salt bath nitriding temperatures were used, with the corresponding time cycles selected to provide various “compound layer” (CL) depths. (As used herein, the term “hardenable”, or “hardened stainless steel” refers to transformation hardening by the formation of martensite, not precipitation hardening by the precipitation of carbides.). 3. Process quality control measures include: Complete control of process sequence, including salt bath temperature and composition, polishing, and post-treatment parts handling The heat requirements for liquid are lower than for the gas technique, and the hardened compound on the surface of the component is thicker. Like carbides, nitrides are often refractory materials owing to their high lattice energy which reflects the strong attraction of "N 3−" for the metal cation.Thus, titanium nitride and silicon nitride are used as cutting materials and hard coatings. For the 304 stainless, the first is at T1, which occurs at a temperature of about 815° F. The higher transition temperature, known as T2, occurs at about 905° F. It has been postulated that, below 815° F., a microstructural phase termed as ‘S’ phase and defined as expanded austenite exists totally, and provides excellent corrosion resistance. The surface of the four hour specimen appeared to be file hard. A proprietary nitriding salt bath has the following composition by weight: 60 to 61% NaCN, 15.0 to 15.5% K 2 C O 3 , and 23 to 24% KCI. Liquid nitriding requires precise control of the treatment process. Low temperature nitriding salt and method of use. The nitride phase has corrosion resistance that is significantly reduced over that of the ‘S’ phase. In use, the composition is fused and then maintained at the desired temperature, the selection of which will be discussed presently, and the workpiece to be nitrocarburized is immersed in the fused bath for the desired period, the selection of which period also will be discussed later. Two specimens or samples were treated according to each of the conditions of temperature and time indicated in Table I below. Tools and small components are often liquid-nitrided. These salts and chemicals are formulated using optimum quality ingredients that are sourced from the renowned vendors in the market. Table 8.10 gives composition of some nitriding baths. Salt bath nitriding —also known as ferritic nitrocarburizing (FNC)— is one of the most popular ways to achieve these results, but it isn’t the only way. With respect to austenitic stainless steel, it is possible to provide a hard layer on the surface thereof at temperatures low enough such that the inherent corrosion resistance (which is high) is not adversely affected. determined by the composition of the liquid.A heat source would be compulsory to drive the nitrogen into the steel surface. Nitrogen has partial solubility in iron. The nitriding process (Fig. Moreover, even though a significant depth of the compound layer formed on the surface of hardenable stainless steel, such as the 400 series, results in increased corrosion resistance, if this is achieved at a temperature above the tempering temperature, a reduction in core hardness will result; and 1075° F., a conventional salt bath nitriding temperature, is above the desired tempering temperature of some products. For temperatures between 750° F. and 950° F., the salt bath had a weight percentage of about 48% cyanate ion and at least 1% by weight of carbonate ion with the potassium to sodium ratio being 3.9 to 1.0. Normally the cyanide salt is melted and aged at the nitriding temperature for 12-24 hours, before the parts are immersed into the bath. Gas nitriding can be applied to unalloyed steels and irons to produce a corrosion- and wear-resistant nitride layer. Thus, a benefit is derived in using the present invention in treating austenitic grade stainless steels in that a hardened case can be provided without sacrificing the corrosion resistance and, in the case of hardenable stainless steel, it is possible to maintain the corrosion resistance obtained at normal nitrocarburizing temperatures while not adversely affecting the core hardness in the hardened and tempered condition. Liquid nitriding is the process of diffusion enrichment of the surface layer of a part with Nitrogen provided by a molten cyanide base salt (extremely toxic substance). 2 is a set of curves showing the depth of the outer contact layer or case formed at various temperatures of salt bath nitriding for various times, both with conventional nitrocarburizing salt and the salt of the present invention, on samples of 304 stainless steel; FIG. Again, the composition of the salt bath for those specimens treated at 750° F. to 950° F. was a salt bath according to the present invention, including alkaline metal cyanate with 48% cyanate ion and at least 1% carbonate ion with the potassium to sodium ratio being 3.9 to 1.0. With the foregoing description in mind, however, it is understood that this description is made only by way of example, that the invention is not limited to the particular embodiments described herein, and that various rearrangements, modifications, and substitutions may be implemented without departing from the true spirit of the invention as hereinafter claimed. atmosphere composition, steel surface condition, alloy composition and the pre-nitriding steel microstructure. Those specimens that were treated in conventional salts for salt bath nitriding had about 35% cyanate ion, with the potassium sodium ratio being 3.9 to 1.0 and at least about 1% carbonate. Liquid pressure nitriding is a process in which anhydrous ammonia is introduced into a cyanide-cyanate bath. 5 is a curve showing the core hardness of 416 stainless steel after salt bath nitriding in various salts for various times. The secret of the nitriding process is that it does not require a phase change from ferrite to austenite, nor does it require a further change from austenite to martensite. The alkali metal cyanate and alkali metal carbonate are preferably either sodium cyanate or potassium cyanate or mixtures of sodium and potassium cyanate, preferably mixtures of sodium and potassium cyanate wherein the ratio of the potassium to the sodium is about 3.9 to 1. Liquid nitriding is the process of diffusion enrichment of the surface layer of a part with Nitrogen provided by a molten cyanide base salt (extremely toxic substance). In FNC and Gas Nitriding, the source of Nitrogen comes from Ammonia. The process is carried out at the temperatures 950-1075°F (510-580°C) for about 4 hour. Underneath the white layer we have a diffusion case or diffusion zone. It provides similar advantages as gas nitriding. The workpiece is immersed in the fused bath and left in there for a time, typically from about two hours to about eight hours until a satisfactory compound layer or case is formed. However, when the bath is not in use, and the bath is aerated, this cyanide is converted, at least in part, to cyanate. Liquid Nitriding: It is a nitriding process using molten salt baths containing cyanides or cyanates in range of 510 to 580°C. Salt bath nitriding uses the melting of salt containing rich nitrogen source. PROCESS AND TECHNICAL DETAILS Salt Bath Nitriding is performed at 560° - 570° C following necessary heat … A molten-salt bath for nitriding mechanical steel parts, essentially consisting of the following (the contents being expressed in wt %): 25 to 60 wt % of alkali-metal chlorides; 10 to 40 wt % of alkali-metal carbonates; 20 to 50 wt % of alkali-metal cyanates; and a maximum of 3 wt % of cyanide ions (formed during the use of the bath), wherein the total of the contents is 100 wt %. With 400 series stainless steel, increased corrosion resistance is achieved by immersion for between four and six hours at 950° F. This invention relates generally to providing hard cases on ferrous workpieces and, more particularly, to an improved salt and method of use thereof for forming hard cases on ferrous workpieces, especially stainless steels and, more especially, austenitic and hardenable stainless steels. Salt bath nitriding uses the melting of salt containing rich nitrogen source. Salt Bath Nitriding is performed at 560° - 570° C following necessary heat … 1075° F. and above, in conventional salt baths has resulted in a substantial and significant reduction in corrosion resistance, thus forcing the designer of the part or the structure using a nitrocarburized surface to sacrifice corrosion resistance for case hardening, or sacrifice case hardness for corrosion resistance. Both together comprise what is generally referred to as the case. Nitrogen is soluble in iron up to a value of approximately 7% by volume (maximum). In fact, increasing the temperature of the salt bath to about 1166° F. while increasing the depth of the compound layer still resulted in significant degradation of the corrosion resistance of the austenitic stainless steel. At nitrogen contents greater than 8%, the equilibrium reaction product is ε compound, Fe 3 N. Nitrided cases are stratified. The various nitriding processes can be dif-ferentiated mainly by their nitrogen source and the energy supply. The outside layer is called a compound layer (or white layer) and its thickness generally falls between zero and 0.001″ (25 µm). In an alkali metal cyanate mixture, with a potassium to sodium ratio of about 3.9 to 1 by weight, what appears to be a eutectic composition forms. percentage microhardness after salt bath nitriding in the range of 10.8 % to 49.82 %, 14.63 % to 46.68 % for both temperatures 520°C and 580°C, Respectively. The composition is fused and maintained at a temperature of between about 750° F. and about 950° F. depending upon the type of stainless steel to be treated. Uses of nitrides. The process Nitriding is a diffusion process and not a deposition process. The process is carried out at the temperatures 950-1075°F (510-580°C) for about 4 hour. The bath contains sodium cyanide and other salts, which permits an operating temperature of 525 to 565°C. When over saturation occurs, the nitrogen has precipitated out of solution during the cooling stage of the process and has settled at the grain boundary locations in the corner if the component. This tool will be designed to predict the nitride profile as well as the nitrogen concentration profile (i.e. ical composition and final properties and installed a novel process control technology in 1975. (Post treatments referred to as quench-polish-quench, as described above, were performed in some cases.) Nitriding. The composition of the salt bath for those specimens treated at 750° F. to 950° F. was a salt bath according to the present invention, including an alkali metal cyanate with 48% cyanate ion and at least 1% carbonate ion with the potassium to sodium ratio being 3.9 to 1.0. percentage microhardness after salt bath nitriding in the range of 10.8 % to 49.82 %, 14.63 % to 46.68 % for both temperatures 520°C and 580°C, Respectively. Liquid Nitriding (Salt Bath Nitriding) FAQ What is Liquid Nitriding? USA CORPORATION, A CORP. OF OHIO, OHIO, ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KOLENE CORPORATION;REEL/FRAME:017125/0375, ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:H.E.F. Nitriding process for ferrous metal parts, with improved corrosion resistance. This involves quenching the workpiece as it comes out of the nitrocarburizing bath at 750° F.-1166° F. in an oxidizing bath at 750° F. for a period of 20 minutes followed by a mechanical polish, followed by a second quench in the same bath at the same temperature for a time of 20 minutes. The nascent nitrogen diffuses into the surface of steel. The hardened and tempered samples of 416 stainless steel were then treated in salt bath nitriding for the times and temperatures indicated in Table II below. It is known that ferritic nitrocarburizing at typical processing temperatures in various media, such as salt bath nitrocarburizing (also called salt bath nitriding) at about 1075° F., enhances the corrosion resistance of carbon steels and low alloy steels, particularly if a post nitrocarburizing treatment, such as a quench-polish-quench, is employed. The composition includes alkali metal cyanate and alkali metal carbonate, wherein the cyanate ion is present in a weight percentage of greater than 45% and less than 55.2%. Liquid nitriding is a subcritical surface enhancement process with one of the longest track records of success of any case hardening technology. Nitriding is a surface-hardening heat treatment that introduces nitrogen into the surface of steel at a temperature range (500 to 550°C, or 930 to 1020°F), while it is in the ferrite condition. Salt-bath nitriding is commonly restricted to 4 hours, because the density of pores increases with time. Also, it is known that significant improvement in corrosion resistance over the as-processed corrosion resistance for nitrocarburized 420 grade and other hardenable stainless steel can be achieved by increasing the depth of the case hardened or compound layer on the surface thereof. At 750° F., the effect of time on diffusion rate between four hours and eight hours is minimal, with the resulting compound layer depth not exceeding about 0.0002 in. The exact amount of carbonate is immaterial, just so there is some carbonate since at least some carbonate must be present to buffer the fused salt to an alkali condition. It is estimated that this file hard surface was probably about HRC 65 (R. Further examination of the 950° F. and 1075 ° F. test specimens disclosed a dark microstructural phase. PATENTED CASE, Owner name: According to the present invention, a composition for nitrocarburizing stainless steel parts and a method for producing a nitride or hard case on such parts using the composition, sometimes referred to as salt bath nitriding, are provided. There are several different nitriding processes such as gas, plasma, and salt bath nitriding. This is a well-known test for hardness wherein a file is applied to the surface of the specimen and, if the surface resists the “biting” action of the file, it is considered to be file hard. The depth of this CL is shown as a function of time and temperature in several curves in FIG. providing a fused bath of alkali metal cyanate, and alkali metal carbonate, wherein said cyanate ion is present in a weight percentage of greater than 45% and less than 55.2%, maintained at a temperature of between 750° F. and 950° F., and immersing a workpiece in said bath for a sufficient time to form a hard case thereon. What is the basic principle of Liquid Nitriding? Preferably, the regenerator is either melamine or urea or a derivative of melamine, such as melam, melem and melom. Salt-bath nitriding is commonly restricted to 4 hours, because the density of pores increases with time. However, comparable treatment of austenitic stainless steels is known to reduce resistance to corrosion. This is not added as a component to the bath. A surface exposed to a nitriding medium will generally form two distinct layers. The corrosion test was performed in accordance with ASTM B-117-90 specifications, using a Singleton Chamber Model PSF22. The phases formed within this surface layer are epsilon (e) and gamma prime (g¢). In alloy steels that contain nitride-forming alloy elements (Cr, Mn, Mo, V, W, Al, Ti) a deeper diffusion layer develops. Method for solution hardening of a cold deformed workpiece of a passive alloy, and a member solution hardened by the method. conversion coatings, passivation of metals using liquids, e.g. The corrosion resistance of the 304 stainless steel is as shown graphically in FIG. If the carbonate is completely depleted by reaction with the regenerator, this can have an adverse effect in that the bath has a propensity to attack the pot material containing the bath, and also in the formation of unwanted and ineffective regenerator material. In other words, the steel remains in the ferrite phase (or cementite, depending on alloy composition) during the complete proce-dure. As can be seen in FIG. 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. Nitriding processes carried out at temperatures below A C1 on the phase diagram do not cause a phase transformation; consequently the hardness of the base material should not be affected. The use of low temperature salt bath nitriding according to this invention does not seem to provide any beneficial effect vis-a-vis precipitation hardened stainless steel, such as 17-4 pH. In performing the test, the test specimens were immersed in the fused bath at various temperatures for various times and then various properties of the test specimens were measured, such as case hardness, case depth and, in the case of hardenable stainless steel, core strength of the specimen. salt baths, liquid suspensions, Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. Using liquids, e.g performed to reveal the differences between both treatments immersed in the market Table I.... Generally referred to as the nitrogen donating medium is a diffusion case or diffusion zone bath a nitrocarburizing.... Carbon are diffused simultaneously into the surface of steel the specimens of the present invention have described... 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