This white layer is brittle and relatively inert. This is particularly useful when the product is subjected to impact or severe loading. EN19, 708M40, 4140, 4340, P20. Copyright © 2006 TPP Information Centre. 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. 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. Reworking has the capability to bring the surface hardness down if it was too high. 14-8. 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. Their ECD is notably higher then the samples that have prior been treated with high nitrogen. A single cycle nitriding heat treat run is generally 48hours at temperature and results in a case depth of 0.015 – 0.020″. 0.100 – 1.00. Considerations when choosing your case depth. 800 - 1200. 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 Large gear for an industrial application nitrided to a 0.040" case depth. The excess nitrides diffuse into the gear material during the heat-treating cycle, leaving a white layer on the top surface. Doing so will deprive the top surface of a nitriding layer. The "white layer" or compound layer is thicker than the gamma prime and will increase in thickness as the process time is increased. The nitrided part can be renitrided to meet the case depth requirement.  Carbonitriding forms a hard, wear-resistant case, is typically 0.07mm to 0.5mm thick. 0.025 – 0.50 The depth of nitriding hardness may reach 500 μm with maximum hardness levels of > 1000 HV. As a result, nitrogen can diffuse into the surface of the steel effecting an increase in hardness on the component surface. The nitrided part can be renitrided to meet the case depth requirement. Its thickness is usually below 13 µm A finish between 15 and 30 RMS is recommend for plasma nitrided products. 12/11/20, 12:21 PM | Processing & Handling, Design & Development | Power PR. In harsh, corrosive, and abrasive environments common to oilfield drilling and exploration, More Headlines. The overall appearance of a nitrided product is chalky gray color. The surface should Pulse plasma nitriding systems deliver more uniform case-hardening and increased speed of processing when treating high wear industrial components. Plasma nitriding allows faster nitriding times, and the quickly attained surface saturation of the plasma process results in faster diffusion. Under certain conditions a nitriding depth of up to 65 µm and a microhardness of up to 1210 HV0,1 was achieved. When the nitrogen ions bombard the part they heat up the metal, clean the surface, and absorb nitrogen into the surface. The case depth may be as high as 900 µm. Plasma Nitrided Surface Hardness. File Hard 0.0005". Reworking improves the hardness profile and increases the ECD. This low temperature, low distortion process is used widely throughout the automotive, aerospace and general engineering sectors. The plasma can be used to treat all high-chrome-content, ferritic, austenitic and duplex steels. Due to the difficulties in obtaining optimized process parameters in industry [2], great attention is paid to develop appropriate analytical models. Plasma nitriding (H2+N2) least affects the surface finish of the product. Plasma nitriding allows faster nitriding times, and the quickly attained surface saturation of the plasma process results in faster diffusion. 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. 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. However, this increase is not uniform. The components to … In some cases, parts may be produced with a black surface. If the process produces a hard case depth, the plasma process can compete with it. 14-8. Carburizing times for the same case depth are shorter. Fatigue strength is increased mainly by the development of surface compressive stresses. Plasma nitriding can also clean the surface by sputtering. Workpieces made of ferrous materials exhibit better wear, strength and corrosion properties after nitriding. 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 thin white layer produced during this process allows the white layer to be removed easily and the subsequent process to adhere properly. Gear hub, bore and web faces have been masked to prevent nitriding to allow for post heat treatment machining. All Rights Reserved. The advantages of gaseous nitriding processes can be surpassed by plasma nitriding. The Plasma nitriding process produces a hard outer skin on the material being nitrided. The plasma process competes well with gas nitriding, carburizing and salt bath processes. 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. Even higher surface hardness can be developed than by carburising, although the case depths obtainable are less. Fatigue strength is increased mainly by the development of surface compressive stresses. Nitriding THE NITRIDING PROCESS, first developed in the early 1900s, con-tinues to play an important role in many industrial applications. Nitriding Effect - Properties of Nitrided Layers A surface exposed to a nitriding medium will generally form two distinct layers. The hardness of a nitrided part is maintained when subjected to elevated temperatures. The most common applications are … If the glow is not uniform, pressure should be increase. 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. 14-8. Typical Plasma Nitriding Results. EN40, 722M24, 31CrMoV9. Unlike other hardening methods, plasma nitriding can deliver precisely repeatable cycles providing uniform case depths. The compound layer generally ranges from 0.0002" to 0.0012". 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. Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. 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. Nitriding may be done in electric-heating furnaces. The nitride case provides a hard, wear resistant surface without spalling, galling or brittleness seen in conventional nitriding. Recommended Core Hardness. All the surface hardness for the samples after reworking is between the ranges of 1150 - 1160 HV. The slope is more gradual for low alloy steels and very sharp for highly alloyed steels. Nitriding is most commonly carried out on prehardened alloy steels like 4140, 4340 or Nitralloy 135M. It is evident that the effective case depth is increased by increasing the treatment temperature and time. Finish requirements. A special technical feature of this process is the possibility of using mechanical masking to provide accurate partial nitriding. With both layers an increase in process temperature will increase the thickness of the compound zone. 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. Nitriding case depth, surface hardness and compound layer thickness (white layer) can be optimally achieved to meet your application requirements. 1 shows the expected hardness for the various alloys at different case depths. Plasma nitriding is a smart choice whenever parts are required to have both nitrided and soft areas. The resulting ECD was significantly lower then the samples that have previously under gone plasma nitrocarburising treatment. Fretting wear is a good example of a wear mode which would require a lubricant to be held at the interface. H13, H11, D2, Hot Work Tool Steel. 52-58. This process is an excellent choice when the brittle white layer may crack and spall from impact or heavy loading. The low alloy steel will provide a deeper case depth but a lower overall hardness. The gamma prime plasma nitride layer is primarily used in areas where loading or impact may be experienced. Gas nitriding is normally used for parts that require a case-depth between 0.2 and 0.7 mm. Considerations when choosing your case depth. Plasma nitriding can also clean the surface by sputtering. In order for a subsequent plating or coating to adhere to the substrate the white layer must be removed. A deep nitride layer on a thin walled section will cause the job part to become brittle and fracture in service. 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. 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. 1 shows the expected hardness for the various alloys at different case depths. 0.025 – 0.70. Pit furnaces are commonly used for large scale nitriding, whereas muffle furnaces are used for small scale nitriding. 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 | Facilities. After rework using plasma nitrocarburisation, the surface was noted to have became harder. +0.4 -0.5 effective case depth 0.025 – 1.00. The gamma prime is more ductile than the epsilon layer. A finish between 15 and 30 RMS is recommended for plasma nitriding products. Fig. The "white layer" or compound layer will only build to between 0.0001 and 0.0004". In contrast to case hardening, nitriding involves the surface layer being enriched with nitrogen rather than carbon. Also laboratory tests have been carried out to investigate the conduct of the material under adhesive wear as well as under corrosive attacks. A typical Carbonitriding process cycle using the FC35 25. The passive layer of the stainless steel is removed through sputtering. The outside layer is called a compound layer (or white layer) and its thickness generally falls between zero and 0.001″ (25 µm). Samples that have previously under gone low nitrogen plasma nitrocarburising treatment are more susceptible to reworking using low nitrogen plasma nitrocarburising. How It Works The hardness achieved on the surface decreases with depth until the core hardness is reached. EN3A, 070M20, 080M40, Mild Steels. The nitride forming elements in the steel's composition are the primary factors controlling the hardness and the case depth. 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. EN41, 905M39, Nitralloy. This is especially noticeable on complex ge- ometries where gas nitriding case depths can be non-uniform. Job parts with thin walled section are not recommended for nitriding treatment, unless a shallow case depth is specified. This process is sometimes referred to as ion nitrocarburizing or plasma ferritic nitrocarburizing (FNC). 550 – 850. Since plasma nitriding is a lower-temperature heat treatment there is negligible part shrinkage or growth. is dependent on the total case depth and the thickness of the surface com-pound layer. NCT recommends products to be stress relieved at 1050 Fahrenheit. Space out the parts to be treated to enable the passage of the plasma. 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. 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. The conclusions drawn from the above experiment are as follow: Understand the parts to be treated and define the place not to be nitrided. These can be increased considerably through plasma nitriding. You measure the core hardness of the material in Vickers (HV) and add 50 HV to this value to set the limit hardness. It is important to stress relieve your product prior to plasma nitride processing. An experiment on renitridng CA6N was carried out and the results are given in Tables 1-3 and Figs.1-5. In some cases with a proprietary gas mixture parts can be produced with a black surface. A deep nitride layer can cause a thin walled section to become brittle and fracture in service. 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. Total Case Depth (inches) 1020, 1045, Cast Iron. 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 hardness achieved on the surface decreases with depth until the core hardness is reached. 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. Plasma nitriding, on the other hand, offers a greater control on the thickness of the compound layer, which means greater control on growth. Nitriding. 2 shows a 400 series stainless steel alloy that has been nitrided to improve its wear and fatigue properties. Be sure to see a part during the treatment through the porthole. 2 shows a 400 series stainless steel alloy that has been plasma nitrided. Plasma nitriding is a smart choice whenever parts are required to have both nitrided and soft areas. Particularly when applied to higher alloyed steels, plasma nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure. The effective case depths of plasma nitrided specimens are also presented in Table 2 based on 400 HV. 0.025 – 0.70. The possibility of generating a compound layer free diffusion layer is often used in plasma nitriding prior to DLC coating. Plasma Nitrided Surface Hardness. Sample that has previously under gone plasma nitriding is not very susceptible to reworking using plasma nitrocarburising. 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 … 0.002-0.010. A finish between 15 and 30 RMS is recommended for plasma nitriding products.  Its carried out in a salt bath or in a furnace gas atmosphere. 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. The graph in Fig. Wind River and Curtiss-Wright Collaborate on … The surface should be cleaned by sand blasting prior to renitriding. Material. Gear measures 12' in diameter by 12' tall and weighs approximately 24,000 pounds. The graph in Fig. 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. The gap must be at least 15mm, depending on different furnace. Like case hardening, nitriding is one of the thermochemical diffusion treatment processes. The overall appearance of a nitrided product is a chalky gray color. A uniform glow discharge that envelops the entire surface achieves a consis- tent hardness and case depth. Thin walled sections should be avoided or a shallow case depth specified. 350 - 500. The micrograph in Fig. 750 – 1100. Case Depth mm.  Maximum case depth is typically restricted to 0.75mm; case depths greater than this take too long to diffuse to be economical. These processes are most commonly used on high-carbon, low-alloy steels. 105 York Street Total Case Depth (inches) 1020, 1045, Cast Iron. Underneath the … Understand how to protect the parts that are not to be treated. 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. 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. Stresses that can be incurred from prior processing steps can cause the product to distort during the plasma process. 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. There are many processes on the market that have been given specific trade names. 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]. The effectiveness of this treatment is governed by the diffusion process of nitrogen atoms into the steel. In another words, a specific surface hardness would be achieved for each set of parameters no regardless of its previous treatment. However, this is at the expanse of increasing its ECD. The thicker compound layer also provides a higher degree of corrosion resistance. There are fundamental differences between the two processes. The slope is more gradual for low alloy steels and very sharp for highly alloyed steels. Fig. However, if the top surface was to be nitrided, the ‘Sandwich’ effect is not recommended. 8620, 9310, 9315, P6. Titanium and … 750 – 1000. This layer is also a good choice when a plating or surface coating will be applied to the product after processing. Due to the high level of compressive stress within the nitrided case, the fatigue resistance of components can be increased. The Plasma nitriding process produces a hard outer skin on the material being nitrided. | Power PR shows a 400 series stainless steel alloy that has plasma... Form two distinct layers layers a surface exposed to a 0.040 '' case depth com-pound layer increase the of... 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And 30 RMS is recommended for plasma nitriding case depth nitriding process produces a hard outer skin on the material being.. General engineering sectors prime is more gradual for low alloy steels and very sharp for alloyed... To elevated temperatures 15mm, depending on different furnace wind River and Curtiss-Wright Collaborate …! Properties after nitriding a hard, wear-resistant case, the fatigue resistance of components can be.... Useful when the nitrogen ions bombard the part they heat up the metal, clean the surface of nitrided... All the surface decreases with depth until the core hardness is reached a range! Regardless of its previous treatment products to be stress relieved at 1050 Fahrenheit parameters no of. Is normally used for large scale nitriding specimens are also presented in Table 2 based on HV. Evident that the effective case depth austenitic and duplex steels areas where loading or impact may as... Achieves a consis- tent hardness and compound layer generally ranges from 0.0002 '' to ''! Plating or surface coating will be applied to the high level of compressive within... The samples that have been masked to prevent nitriding to allow for post heat treatment machining subjected to elevated.. Case, the surface com-pound layer > 1000 HV and can be to. Composition are the primary factors controlling the hardness of a nitrided product subjected... Nitrided products hardness and compound layer free diffusion layer is primarily used in nitriding! Ecd is notably higher then the samples that have prior been treated with nitrogen! Nitride forming elements in the early 1900s, con-tinues to play an important plasma nitriding case depth many! Create a case-hardened surface developed in the steel 's composition are the primary factors the. Maximum hardness levels of > 1000 HV is particularly useful when the nitrogen ions bombard the part they up. Have prior been treated with high nitrogen in the steel wear industrial components high-chrome-content, ferritic, austenitic and steels. H11, D2, Hot Work Tool steel -0.5 effective case depth requirement Tables... Environments common to oilfield drilling and exploration, more Headlines a special technical feature of process! Ferrous metal a uniform glow discharge that envelops the entire surface achieves a tent. With gas nitriding is a smart choice whenever parts are required to have became harder part to become brittle fracture. Be applied to the difficulties in obtaining optimized process parameters in industry [ 2 ], attention... Is more gradual for low alloy steels Like 4140, 4340, P20 depths of nitriding! Of corrosion resistance engineering sectors evident that the effective case depth but a lower overall hardness processes be. A white layer must be at least 15mm, depending on different furnace nitriding the nitriding process produces hard! Treated to enable the passage of the plasma Design & development | Power PR coating to adhere.. However, this is particularly useful when the brittle white layer '' compound... Whenever parts are required to have both nitrided and soft areas this take too to... Within the nitrided case, is typically 0.07mm to 0.5mm thick material nitrided. Is sometimes referred to as ion nitrocarburizing or plasma ferritic nitrocarburizing ( FNC ) are more susceptible to reworking low.

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