Papers by Keyword: Nitriding

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Authors: D. Zeng, S. Yang, Zhi Dong Xiang
Abstract: This study is an attempt to codeposit N and Cr into the surface of austenitic stainless steels by pack cementation process to simultaneously increase their surface hardness and corrosion resistance. The pack powders were prepared using Cr2N powder as a source of both N and Cr, NH4Cl as activator and Al2O3 as inert filler. Specimens of the AISI204 austenitic stainless steel were treated in the 2 wt% NH4Cl activated 15Cr2N-85Al2O3 (wt%) pack at 1100 °C for different times. It was demonstrated that a top Cr2N layer with a Cr enriched zone underneath can be formed on the steel surface via the vapour phase generated in the activated powder pack. The effect of adding Cr powder into the pack powders on the surface layer formation and on the hardness profile at the cross-section of the specimen surface was also investigated. Hardness values of more than 1800 HV were obtained at the outermost surface of the treated specimen.
1751
Authors: Shen Yao Lin, Jian Min Zeng, Ping Chen, Zhuo Yi Lin
Abstract: Nitriding is one of the most efficient methods used to enhance the service life of aluminum extrusion dies. In this paper, a new nitriding process has been introduced that is characterized by that 4Cr5MoSiV1 steel, a typical material used for extrusion dies, was nitrided by using two-stage nitriding process. The microstructures of nitrided layer have been analyzed by means of optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and microhardness (MH). The results show that pre-heat treatment on the 4Cr5MoSiV1 steel extrusion die can be carried out under the condition of quenching at 1040 °C, double tempering at 600 °C and 560 °C for 2 hours each. Operating parameters of two-stage nitriding are set as follow: stage one, 520 °C for 6 hours, the flow rate of NH3 of 0.6 m3/h; nitriding pressure of 453 Pa and stage two, 580 °C for 8 hours, the flow rate of NH3 of 0.35 m3/h; nitriding pressure of 453 Pa.
1651
Authors: J.R Deepak
Abstract: Nitriding is the most common surface engineering technique that is being used in Titanium alloys for improving their surface properties, viz hardness, wear resistance, etc. Ti6Al4V (Grade 5) Titanium Alloy is a super alloy that exhibits excellent mechanical strength; it is highly resistance to creep at very high temperatures which maintains good surface stability. It is resistant to corrosion and oxidation. The main objective of this review paper is to study the recent research works carried on Nitriding of Ti6Al4V alloy by using, viz gas Nitriding and laser Nitriding. This process is used in the surface hardening of machine parts such as aircraft engine parts, crank pins, valve seats, gears, bush, aero engine cylinders, aero crank shafts. Gas Nitriding is a diffusional technique in which the nitrogen atoms are diffused into the surface of the metal to obtain hard surface. By Laser Nitriding is a diffusional technique by which the surface properties of the titanium alloy is enhanced. Laser nitriding process comprises of various stages, viz, transport of heat, melting effect, diffusion and convection effect. By Nitriding technique the surface hardness of super alloys like Titanium Alloy Ti6Al4V Grade 5 can be increased by increasing the hardness on the surface there by its scope of application is widened. In this paper a literature survey is carried out and the recent research works on surface engineering of Ti6Al4V alloy using gas and laser Nitriding technique is summarized.
618
Authors: Je Wook Chae, Sung Bae Lee, Chan Lee, Hyun Jun Kim, Young Shin Lee
Abstract: This paper includes a study on the surface treatments of the barrel of small arms with an aim at improving resistance of corrosion and wear. The inner surface of the barrel is Cr plated or nitrided to improve the performance under the firing. The endurance test was conducted to compare the wear resistance of standard barrel (the non surface treatment barrel), the Cr plating barrel and the nitriding barrel. The wear resistance is evaluated by inner diameter of the barrel, muzzle velocity and dispersion during the firing. And the salt water immersion test was conducted to estimate the corrosion resistance. As the results of the tests, the Cr plating barrel is superior to the NST barrel and the nitriding barrel in a view of corrosion and wear.
631
Authors: Hisao Fujikawa, Takanori Watanabe
Abstract: Air Water Incorporated Japan (AWI) has succeeded in developing and commercializing new surface treatment technologies. One of them is the NV Nitriding process. Through an activation treatment using fluorine-based gas for the surface treatment of metals before the nitriding treatment, it is possible to remove the oxide film, such as the passive film, formed on stainless steels and Ni-based alloys and also to nitride these alloys on a mass-production scale. The activation effect afforded by fluoride enables nitriding at a temperature about 150°C lower than other conventional processes, achieving minimal thermal deformation and strain. Also, with this activation process, the range of selection of nitriding conditions such as temperature, gas composition and heat pattern has been considerably extended to enable the formation of a nitride layer optimum for the required characteristics of the treated metals. That is, this process can control the thickness of the nitride compound layer. NV Pionite treatment also has been developed as the soluble carbon diffusion process by which to ensure high corrosion resistance and high hardness in austenitic stainless steels using the above activation treatment.
161
Authors: Kuk Tae Youn, Young Mok Rhyim, Jong Hoon Lee, Chan Gyu Lee, Yun Chul Jung
Abstract: It is well known that the main failure mechanisms in die-casting mould are heat checking due to thermal fatigue and melt-out caused by chemical reaction between die and molten alloys. Thermal fatigue tests were carried out using the thermal cycle simulator to establish the proper method to estimate the thermal fatigue resistance of hot die steel. In this study, the thermal shock tester consisted of induction heating and water spray cooling unit was constructed to evaluate thermal crack propagation resistance and the sum of crack length per unit specimen length, Lm is proposed as the index representing the susceptibility to crack initiation and propagation. Also, new concept of measurement for the melt-out behavior was suggested. AISI H13 hot work tool steel was solution treated and tempered at various temperatures, to control the hardness and toughness that have effect on the behavior of thermal crack propagation. The result of thermal fatigue test showed that there is optimum value of hardness and impact energy to maximize the thermal crack propagation resistance. The influence of nitriding on melt-out resistance was also investigated. The dissolution rate due to melt-out phenomenon tended to be smaller for thicker compound layer. Furthermore, the resistance to melt-out was affected by the compound layer thickness rather than that of diffusion layer. The results of the both tests properly reflect the effect of materials properties on failure modes of die-casting mould and it means those test methods are suitable to evaluate the durability of hot work tool steel for die-casting.
701
Authors: Kuk Tae Youn, Young Mok Rhyim, Jong Hoon Lee, Young Sang Na, Wee Do Yoo, Chan Gyu Lee
Abstract: For hot die steel, failure is mostly caused by heat checking and melt-out on its surfaces which are in contact with molten metals. In the present research, resistances to melt-out and heat checking of surface modified H13 hot die steels, such as gas nitriding(GN) and micro-blasting(MB), were investigated. The evaluation of melt-out behavior was carried out by measuring the mean depth from the original surface after immersion. To examine the thermal fatigue resistance, a cyclic thermal shock system consisting of induction heating and water spray quenching was constructed. The value of Lm is proposed as the index representing the susceptibility to crack initiation and propagation. The melt-out depth was the lowest for the GN treated surface. MB-GN and MB-GN-MB treated specimens also showed good resistance to melt-out. In the case of GN treatment, while the white layer was completely melted out, the diffusion layer still existed even after immersion for 43 hours. This implies that nitriding significantly reduced the rate of melt-out. From the total crack number, it is seen that crack initiation was reduced to the extent of half after surface treatment. This result means that the residual compressive stress and nitrided layer were beneficial to crack initiation resistance.
443
Authors: Hasan Güleryüz, Erdem Atar, Fared Seahjani, Hüseyin Çimenoğlu
Abstract: In this paper, diffusional surface hardening processes utilized to overcome the poor tribological performance of titanium and its alloys is briefly introduced. More specifically, surface treatments known as thermal oxidation, nitriding and boriding offering the advantage of producing graded surfaces comprising hard compound layer and diffusion zone by diffusion of interstitial atoms (oxygen, nitrogen and boron) are overviewed.
103
Authors: Myrna Ariati, Rizki Aldila
Abstract: In metal forming process by die casting method, nitriding plays an important role in increasing the surface hardness. The influence of shot peening and shot blasting to the modified. H13 tool steel before nitriding process has been studied. Nitriding has been done in a gas vacuum furnace, at temperature of 510°C for 5 hours. Shot peening was conducted by using steel balls with a pressure of 461 kPa. Shot blasting has been done after shot peening using SiC particles. Characterization of the sample surface before and after the variation process is focused on changing the microstructure, micro hardness distribution, depth and composition nitriding layer. It has been found that shot peening prior to nitriding increase the maximum surface hardness to 1196 HV and effective depth of diffusion layer to 72 μm. Meanwhile, the nitriding without any prior surface treatment produces a maximum hardness of HV 1101.4 with effective depth of diffusion layer of 54 μm. Shot peening prior to nitriding produces white layer thickness of 4.1 μm thicker compared to white layer developed in nitriding without shot peening which produces 3.7 μm. While on nitrided material without any preceded surface treatment did not reveal any white surface layer.
313
Authors: Mazhyn Skakov, Bauyrzhan Rakhadilov, Erlan Batyrbekov, Michael Scheffler
Abstract: In the article changes in the structure and mechanical properties of R6M5 steel surface layer after electrolytic-plasma nitriding are shown. The optimal mode of electrolytic-plasma nitriding of R6M5 high-speed steel in electrolyte based on carbamide, which allows saturation of the surface with nitrogen from low-temperature plasma and get the modified layer of high hardness and wear-resistance. It is established, that after electrolytic-plasma nitriding reduced R6M5 steel wear rate and increases its resistance to abrasive wear. Perspectivity of use an electrolytic-plasma nitriding method to improve performance cutting tools made from R6M5 steel is shown.
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