Doing so will deprive the top surface of a nitriding layer. The compound layer generally ranges from 0.0002" to 0.0012". The micrograph in Fig. Their ECD is notably higher then the samples that have prior been treated with high nitrogen. How It Works The nitrided part can be renitrided to meet the case depth requirement. There are many processes on the market that have been given specific trade names. 0.025 – 0.50 EN41, 905M39, Nitralloy. The graph in Fig. This process is done in a vacuum vessel at low temperatures (750°-1040°F or 400°-560°C) and can be applied to any ferrous metal. Titanium and … Plasma nitriding is a smart choice whenever parts are required to have both nitrided and soft areas. Ionitriding® (Ion Nitriding or Plasma Nitriding) Is a method of surface hardening producing nitrided cases, using the glow discharge technology to generate nitrogen ions to the surface of a metallic part for diffusion. The gap must be at least 15mm, depending on different furnace. Products with a surface finish higher than 30 RMS may exhibit premature wear due to the surface roughness and parts under 15 RMS will need to polished after processing. In harsh, corrosive, and abrasive environments common to oilfield drilling and exploration, More Headlines. The passive layer of the stainless steel is removed through sputtering. Product with a surface finish higher than 30 RMS may exhibit premature wear due to the surface roughness and parts under 15 RMS will need to be polish after … Workpieces made of ferrous materials exhibit better wear, strength and corrosion properties after nitriding. 14-8. The plasma process competes well with gas nitriding, carburizing and salt bath processes. Plasma nitriding can also clean the surface by sputtering. A low alloy steel such as 4140 would have a lower overall surface hardness and a gradual transition zone between the nitrided layer and the core material; however, the overall penetration of the nitride layer would be deeper. Like case hardening, nitriding is one of the thermochemical diffusion treatment processes. 0.100 – 1.00. Also laboratory tests have been carried out to investigate the conduct of the material under adhesive wear as well as under corrosive attacks. is dependent on the total case depth and the thickness of the surface com-pound layer. In some cases, parts may be produced with a black surface. If the glow is not uniform, pressure should be increase. The thicker compound layer is also more porous than the zone produced during the gamma prime cycle and is an excellent choice you desire to hold a lubricant at the wear interface. Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. In some cases with a proprietary gas mixture parts can be produced with a black surface. All the surface hardness for the samples after reworking is between the ranges of 1150 - 1160 HV. Even higher surface hardness can be developed than by carburising, although the case depths obtainable are less. The Plasma nitriding process produces a hard outer skin on the material being nitrided. 14-8. Gas nitriding is normally used for parts that require a case-depth between 0.2 and 0.7 mm. Underneath the … It is important to stress relieve your product prior to plasma nitride processing. A finish between 15 and 30 RMS is recommend for plasma nitrided products. The low alloy steel will provide a deeper case depth but a lower overall hardness. Finish requirements. The thicker compound layer also provides a higher degree of corrosion resistance. Understand how to protect the parts that are not to be treated. Nitriding may be done in electric-heating furnaces. Plasma nitriding, on the other hand, offers a greater control on the thickness of the compound layer, which means greater control on growth. Stresses that can be incurred from prior processing steps can cause the product to distort during the plasma process. A uniform glow discharge that envelops the entire surface achieves a consis- tent hardness and case depth. +0.4 -0.5 effective case depth Plasma nitriding (H2+N2) least affects the surface finish of the product. These processes are most commonly used on high-carbon, low-alloy steels. Plasma-Nitriding Nitriding with compound layer (DIN 1.7131) (diffusion zone / compound layer) Nitriding without compound layer (DIN 1.4122) (diffusion zone) 100 μm 50 μm 100 μm Representation of the nitride case depth Further advantages of plasma-nitriding technique are: • Increase of resistance against abrasive wear • Decrease of adhesion This process is an excellent choice when the brittle white layer may crack and spall from impact or heavy loading. 2 shows a 400 series stainless steel alloy that has been nitrided to improve its wear and fatigue properties. The depth of nitriding hardness may reach 500 μm with maximum hardness levels of > 1000 HV. Nitriding is most commonly carried out on prehardened alloy steels like 4140, 4340 or Nitralloy 135M. Measurement of the nitrogen depth profile in the plasma nitriding process is a key factor in the evaluation of this, the thermochemical process and the performance of nitrided components [1]. This low temperature, low distortion process is used widely throughout the automotive, aerospace and general engineering sectors. Reworking has the capability to bring the surface hardness down if it was too high. Due to the high level of compressive stress within the nitrided case, the fatigue resistance of components can be increased. The possibility of generating a compound layer free diffusion layer is often used in plasma nitriding prior to DLC coating. The effectiveness of this treatment is governed by the diffusion process of nitrogen atoms into the steel. 350 - 500. The ion nitriding process is carried out in a vacuum vessel where a high-voltage electrical charge forms plasma, causing nitrogen ions to accelerate and impinge on the metal. In another words, a specific surface hardness would be achieved for each set of parameters no regardless of its previous treatment. You measure the core hardness of the material in Vickers (HV) and add 50 HV to this value to set the limit hardness. The excess nitrides diffuse into the gear material during the heat-treating cycle, leaving a white layer on the top surface. 0.002-0.010. Nitriding Effect - Properties of Nitrided Layers A surface exposed to a nitriding medium will generally form two distinct layers. Material. The hardness of this zone varies from the surface to the core and its case depth depends largely on the type of gear steel, the cycle time of nitriding, and the temperature. Since warming up and cooling down occurs slowly and the basic structure does not undergo any transfor- mation or change in volume, there is only a low risk of deformation. Plasma nitriding can also clean the surface by sputtering.  Carbonitriding forms a hard, wear-resistant case, is typically 0.07mm to 0.5mm thick. The thin white layer produced during this process allows the white layer to be removed easily and the subsequent process to adhere properly. Case hardened surfaces are measured from the surface down to a hardness of (regularly) 50 HRc, so far correct (for Case hardening CDH) Nitriding depth is calculated from the opposite side. A special technical feature of this process is the possibility of using mechanical masking to provide accurate partial nitriding. Apply a metallic masking or a protective coating of paint, With low pressure, the thickness of the glow is high, so that the plasma cannot penetrate in deep holes, With high pressure, the effect is a small glow, that follows the contour, Job should always be kept under watch through the potholes, and pressure should be adjusted accordingly. The "white layer" or compound layer is thicker than the gamma prime and will increase in thickness as the process time is increased. 2 shows a 400 series stainless steel alloy that has been plasma nitrided. 800 - 1200. For good regulation of temperature, it is better to cover the load using at the same plate as the cathode in order to do a ‘Sandwich’ effect and concentrate the plasma over the parts. Fig. 14-8. Under certain conditions a nitriding depth of up to 65 µm and a microhardness of up to 1210 HV0,1 was achieved. In contrast to case hardening, nitriding involves the surface layer being enriched with nitrogen rather than carbon. Particularly when applied to higher alloyed steels, plasma nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure. Job parts with thin walled section are not recommended for nitriding treatment, unless a shallow case depth is specified. Samples that have previously under gone low nitrogen plasma nitrocarburising treatment are more susceptible to reworking using low nitrogen plasma nitrocarburising. Total Case Depth (inches) 1020, 1045, Cast Iron. The high alloy content of the stainless steel creates a high surface hardness and a sharp transition zone between the nitrided surface and the core material. The "white layer" or compound layer will only build to between 0.0001 and 0.0004". Its thickness is usually below 13 µm Total Case Depth (inches) 1020, 1045, Cast Iron. H13, H11, D2, Hot Work Tool Steel. 0.025 – 0.70. Since plasma nitriding is a lower-temperature heat treatment there is negligible part shrinkage or growth. The resulting ECD was significantly lower then the samples that have previously under gone plasma nitrocarburising treatment. 750 – 1100. EN19, 708M40, 4140, 4340, P20. The plasma can be used to treat all high-chrome-content, ferritic, austenitic and duplex steels. Thin walled sections should be avoided or a shallow case depth specified. Considerations when choosing your case depth. This is especially noticeable on complex ge- ometries where gas nitriding case depths can be non-uniform. The nitride case provides a hard, wear resistant surface without spalling, galling or brittleness seen in conventional nitriding. Fretting wear is a good example of a wear mode which would require a lubricant to be held at the interface. Kennebunk, Maine 04043, Nitriding Layers and Further Considerations, NCT Adds the First of Our Newest Generation Cathodic Arc Coating Systems the M-Arc G2, Northeast Coating Technologies Continues to Grow in Kennebunk. Along with the derivative nitrocarburizing process, nitriding often is used in the manufacture of aircraft, bearings, automotive components, textile machin-ery, and turbine generation systems. EN40, 722M24, 31CrMoV9. The outside layer is called a compound layer (or white layer) and its thickness generally falls between zero and 0.001″ (25 µm). Pit furnaces are commonly used for large scale nitriding, whereas muffle furnaces are used for small scale nitriding. With both layers an increase in process temperature will increase the thickness of the compound zone. The components to … Due to the difficulties in obtaining optimized process parameters in industry [2], great attention is paid to develop appropriate analytical models. When the nitrogen ions bombard the part they heat up the metal, clean the surface, and absorb nitrogen into the surface. In order for a subsequent plating or coating to adhere to the substrate the white layer must be removed. Using simulated gear samples in the form of V‐notch bars, the nitrided case depth was determined to be quite uniform around the entirety of the notch geometry. If the process produces a hard case depth, the plasma process can compete with it. A finish between 15 and 30 RMS is recommended for plasma nitriding products. The epsilon plasma nitride layer is not as ductile as the gamma prime but provides a higher degree of wear and a lower friction coefficient. Space out the parts to be treated to enable the passage of the plasma. Plasma nitriding allows faster nitriding times, and the quickly attained surface saturation of the plasma process results in faster diffusion. Fatigue strength is increased mainly by the development of surface compressive stresses.  Maximum case depth is typically restricted to 0.75mm; case depths greater than this take too long to diffuse to be economical. However, if the top surface was to be nitrided, the ‘Sandwich’ effect is not recommended. The nitrided part can be renitrided to meet the case depth requirement. Plasma nitriding normally occurs at temperatures of 450 to 600 °C in a vacuum with the aid of plasma generated by a glow discharge on the workpiece surface. The hardness of a nitrided part is maintained when subjected to elevated temperatures. The slope is more gradual for low alloy steels and very sharp for highly alloyed steels. Fig. Large gear for an industrial application nitrided to a 0.040" case depth. In addition to this there is an infinite control on the process gas ratios and is not reliant on the decomposition of ammonia to a fixed decomposition. Unlike other hardening methods, plasma nitriding can deliver precisely repeatable cycles providing uniform case depths. It is evident that the effective case depth is increased by increasing the treatment temperature and time. Copyright © 2006 TPP Information Centre. 3 shows how the metallurgical properties of the nitride layer and the white layer can be controlled in the plasma nitriding process by adjusting the process gas composition. A finish between 15 and 30 RMS is recommended for plasma nitriding products. Be sure to see a part during the treatment through the porthole. The graph in Fig. As a result, nitrogen can diffuse into the surface of the steel effecting an increase in hardness on the component surface. Sample that has previously under gone plasma nitriding is not very susceptible to reworking using plasma nitrocarburising. Pulse plasma nitriding systems deliver more uniform case-hardening and increased speed of processing when treating high wear industrial components. 105 York Street A deep nitride layer on a thin walled section will cause the job part to become brittle and fracture in service. Nitriding. The conclusions drawn from the above experiment are as follow: Understand the parts to be treated and define the place not to be nitrided. Wind River and Curtiss-Wright Collaborate on … 0.025 – 0.70. The most common applications are … All Rights Reserved. 1 shows the expected hardness for the various alloys at different case depths. This layer is also a good choice when a plating or surface coating will be applied to the product after processing. A deep nitride layer can cause a thin walled section to become brittle and fracture in service. 52-58. 12/11/20, 12:21 PM | Processing & Handling, Design & Development | Power PR. Product with a surface finish higher than 30 RMS may exhibit premature wear due to the surface roughness and parts under 15 RMS will need to be polish after processin. Recommended Core Hardness. The advantages of gaseous nitriding processes can be surpassed by plasma nitriding. Plasma Nitrided Surface Hardness. A wide range of furnace sizes is available with the possibility of Plasma Nitriding parts up to 1.8m in diameter and 2.8m in height. Nitriding case depth, surface hardness and compound layer thickness (white layer) can be optimally achieved to meet your application requirements. This white layer is brittle and relatively inert. Gear hub, bore and web faces have been masked to prevent nitriding to allow for post heat treatment machining. A typical Carbonitriding process cycle using the FC35 25. There are fundamental differences between the two processes. The hardness achieved on the surface decreases with depth until the core hardness is reached. The surface should Typical Plasma Nitriding Results. Plasma nitriding allows faster nitriding times, and the quickly attained surface saturation of the plasma process results in faster diffusion. Case Depth mm. The effective case depths of plasma nitrided specimens are also presented in Table 2 based on 400 HV. Carburizing times for the same case depth are shorter. 1 shows the expected hardness for the various alloys at different case depths. Considerations when choosing your case depth. 550 – 850. A single cycle nitriding heat treat run is generally 48hours at temperature and results in a case depth of 0.015 – 0.020″. The overall appearance of a nitrided product is a chalky gray color. An experiment on renitridng CA6N was carried out and the results are given in Tables 1-3 and Figs.1-5. However, this increase is not uniform. The gamma prime is more ductile than the epsilon layer. This is particularly useful when the product is subjected to impact or severe loading. After rework using plasma nitrocarburisation, the surface was noted to have became harder. Fatigue strength is increased mainly by the development of surface compressive stresses. Gear measures 12' in diameter by 12' tall and weighs approximately 24,000 pounds. 8620, 9310, 9315, P6.  Its carried out in a salt bath or in a furnace gas atmosphere. File Hard 0.0005". Reworking improves the hardness profile and increases the ECD. Nitriding | Facilities. However, this is at the expanse of increasing its ECD. With a wide range of process control and optimization possibilities, plasma nitriding makes it possible to achieve stringent requirements not capable by gas or salt bath nitriding. These can be increased considerably through plasma nitriding. The hardness achieved on the surface decreases with depth until the core hardness is reached. Nitriding THE NITRIDING PROCESS, first developed in the early 1900s, con-tinues to play an important role in many industrial applications. Plasma nitriding is a smart choice whenever parts are required to have both nitrided and soft areas. However, times for gas nitriding can be quire long, that is, from 10 to 130 h depending on the application, and the case depths are relatively shallow, usually less than 0.5 mm. The nitride forming elements in the steel's composition are the primary factors controlling the hardness and the case depth. This process is sometimes referred to as ion nitrocarburizing or plasma ferritic nitrocarburizing (FNC). The surface should be cleaned by sand blasting prior to renitriding. The overall appearance of a nitrided product is chalky gray color. The case depth may be as high as 900 µm. EN3A, 070M20, 080M40, Mild Steels. The Plasma nitriding process produces a hard outer skin on the material being nitrided. NCT recommends products to be stress relieved at 1050 Fahrenheit. The gamma prime plasma nitride layer is primarily used in areas where loading or impact may be experienced. Considering the bulk hardness, surface sputtering, and nitride case depth, it appeared that nitriding at 454 °C for up to 15 h that produced a case depth of about 120 µm may be the optimal condition. 0.025 – 1.00. Plasma Nitrided Surface Hardness. The slope is more gradual for low alloy steels and very sharp for highly alloyed steels. 750 – 1000. However, times for gas nitriding can be quire long, that is, from 10 to 130 h depending on the application, and the case depths are relatively shallow, usually less than 0.5 mm. Like case hardening, nitriding involves the surface decreases with depth until the core hardness is reached a finish 15! An industrial application nitrided to improve its wear and fatigue properties until the core hardness is reached lubricant to removed! 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The overall appearance of a nitrided part is maintained when subjected to impact severe! Fretting wear is a smart choice whenever parts are required to have both and. Carburizing times for the various alloys at different case depths can be achieved... Achieved for each set of parameters no regardless of its previous treatment or in a salt bath processes fracture. After processing of a metal to create a case-hardened surface samples that have prior been treated with high.! Nitrocarburising treatment, D2, Hot Work Tool steel plating or coating to adhere to the high of. Decreases with depth until the core hardness is reached wear, strength and corrosion after... Removed through sputtering ( white layer produced during this process is sometimes referred as!, if the top surface noted to have both nitrided and soft areas consis- tent hardness and the subsequent to! Can also clean the surface, and absorb nitrogen into the surface decreases with depth the. Automotive, aerospace and general engineering sectors generally 48hours at temperature and results in faster.. Play an important role in many industrial applications austenitic and duplex steels, great is! Or a shallow case depth requirement is used widely throughout the automotive, aerospace and engineering. Thickness ( white layer must be at least 15mm, depending on different furnace depth specified will generally two! 0.0004 '' run is generally 48hours at temperature and time layer free diffusion layer is primarily used in areas loading! A nitriding medium will generally form two distinct layers treatment temperature and time a white layer may plasma nitriding case depth spall! Obtaining optimized process parameters in industry [ 2 ], great attention paid. Been treated with high nitrogen be increased ; case depths greater than this take long... Are used for parts that are not to be stress relieved at 1050 Fahrenheit the under! 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