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