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In this work, we used mass spectrometry to investigate ammonia (NH3) formed during the nitrocarburizing and nitriding processes of α-Fe sintered and low alloy steel by using d.c. glow discharges in different N2/H2/CH4 gas concentration mixtures. Experiments were conducted using two different configurations: one to collect and analyze species probed primarily in the bulk of the plasma, at a position distant from the heated sample; and the other to collect and analyze species very close to the reactive surface of the heated sample in such a way as to allow the analysis of lower concentration or residence time species, formed at the plasma/sample surface interface. Use of these configurations contributed to the investigation of the physical chemistry involved in the above plasma processes. An exchange the expected stoichiometry in ammonia formation in N2/H2/CH4 mixtures, with a shift towards higher nitrogen consumption, is observed and is interpreted an indication of nitrogen removal from the surface associated with ammonia and carbonitrides/nitrides formation. The present results point to the existence of a correlation between the nitrocarburizing and nitriding processes with respect to the formation of non-stoichiometric ammonia as a product.

Formation of metastable C–, N–, or even Formation of metastable C–, N–, or even C/N– expanded phases can be observed for typical non-equilibrium conditions attained at the plasma assisted thermochemical treatments when temperatures relatively low are used. In present work, kinetics data are considered in a comparative study comprising low-temperature plasma assisted carburizing, nitriding and nitrocarburizing of AISI 420 martensitic stainless steel samples treated at 350, 400, and 450 °C, aiming to put in evidence the main metallurgical differences of the obtained layers. Microstructural characterization and hardness measurement results for untreated and treated sample surfaces show significant difference for the carburized layer growth in relation to that verified for the nitrided and nitrocarburized layers. While the carburized layer is constituted of a thin outer layer and a deep diffusion layer, just the opposite was observed for the other two treatments, id est., formation of thicker outer layers and thinner diffusion layers. Finally, carbide-/nitride-precipitation-free layers were supposedly obtained for samples carburized, nitrided, and nitrocarburized at 350 °C temperature.

In order to resist the high loads, the surfaces and boundary areas of forging dies are nitrided. Up to now, there was no proven knowledge about, which processing parameters respectively which nitrided case leads to the best life time of the tools. In the present work, the influence of nitriding and nitrocarburizing with all their variety of nitrided cases on the lifetime and wear of forging dies was investigated. Eight promising treatments were transferred to forging dies, in order to create a number of different nitrided cases. The tools were used in serial production and their lifetime was determined under real conditions. At the lifetime end, critical parts of the tools were metallographical investigated, in order to find out the wear mechanisms. Finally, a recommendation was developed which nitrided case revealed the best results for a given loading condition.

U diplomskom radu su ispitani alati za ručnu obradu drva brušenjem. Rad se sastoji od teorijskog i eksperimentalnog dijela. U teorijskom dijelu su opisani postupci obrade, dok je u eksperimentalnom dijelu prikazano ispitivanje na uzorcima. Ispitana su četiri uzorka obrađena različitim toplinskim obradama. Ispitani uzorci obrađeni su metodama nitrokarburiranja u solnoj kupki, nitriranja u plazmi, te presvlačenja PACVD postupkom presvlakama titan nitrida (TiN) i titan karbon nitrida (TiCN). Na uzorcima su ispitani gubitak mase prilikom korozije, mikrotvrdoća te mikrostruktura i debljina nitriranog sloja i prevlaka. Na temelju rezultata ispitivanja, najbolja svojstva su postignuta kod ispitnih uzoraka nitrokarburiranih u solnoj kupki Tenifer te kod uzorka prevučenih PACVD postupkom TiN prevlakom. In the graduate thesis properties of nitrided and coated hand tools for wood grinding were tested. The thesis is comprised out of two parts. In the first, theoretical, part methods of surface heat treatment are presented. The second, experimental, part deals with tests conducted on samples. Heat treatments used on hand tools were salt bath nitrocarburizing, plasma nitriding and PACVD coating with TiN and TiCN coats. The samples were tested for loss of mass due to corrosion, microhardness, microstructure, and nitride depth and coat thickness. According to the test results, best properties are reached with samples treated in nitrocarburizing salt bath Tenifer and with samples with PACVD TiN coating.

Porous iron foils were used for synthesizing homogeneous samples of iron carbides and (carbo)nitrides. Homogeneous distributions of interstitial nitrogen and carbon were obtained without long treatment times due to limited required diffusion distances in the porous material. By adjustments of the nitriding and carburizing potentials, tailored nitrogen and carbon contents can be achieved, which allows assessment of a phase stability diagram for the Fe-N-C system, for which available experimental data is limited. Thermal decomposition sequences were established for the various iron carbides and (carbo)nitrides using in situ synchrotron X-ray diffraction. Hägg carbide (χ) and ε-carbonitride, Fe2(N,C)1-z, with high carbon content decompose to cementite (θ) above 850 K, while ferrite (α) forms above 950 K and austenite (γ) above 1025 K. For high nitrogen contents ζ- Fe2(N,C) is transformed to ε from 680 to 770 K, which decomposes to γ′-Fe4(N,C)1+x between 795 and 900 K as nitrogen is released as N2. Ferrite forms above 850 K while austenite may be briefly formed around 900 K.The two iron carbides, cementite and Hägg carbide, exhibit different coefficients of thermal expansion. Below approximately 480 K, cementite is ferromagnetic and a volumetric thermal expansion coefficient of αV = 1.5 × 10−5 K−1 is obtained. The average value in the paramagnetic state is αV = 4.3 (3) × 10−5 K−1. For Hägg carbide the average value is αV = 3.8 (5) × 10−5 K−1 and only a minor change in unit cell volume is observed at the magnetic transition temperature.

Forged low-carbon alloy Co – 27% Cr – 6% Mo – 0.06% C is studied after 2-h plasma nitrocarburizing in a gaseous mixture of 10% CO 2 + 20% N 2 + 70% H 2 at 400, 500 and 600°C. The surface layer and the core are studied by diffractometric analysis and scanning electron microscopy. The microhardness and the tribological characteristics of the alloy are determined. The effect of the temperature of nitrocarburizing on the wear resistance, surface roughness and friction coefficient of the alloy is considered.

A barrel is one of the most tribologically and thermally loaded parts of artillery weapons. The influence of the salt bath nitrocarburizing and hard-chrome plating of three steels used for artillery barrels on their abrasion resistance is studied in this paper. The tested steels are 42CrMo4, 30CrNiMo8, and 36CrNiMo4 in the initial quenched and tempered state. The test results from the ''dry sand/rubber wheel'' method, after 700 m of wear path, showed that the hard-chrome plating of 42CrMo4 and 30CrNiMo8 steels improved their abrasion resistance. In addition, reduced abrasive wear of 42CrMo4 steel samples was also achieved by nitrocarburizing. Hard chrome-plated samples exhibited good wear resistance due to their greater hardness and bigger thickness of the compound zone in comparison with that obtained on nitrocarburized samples.

Several surface modification technologies are typically applied to improve the mechanical properties of the material surface of structural components subjected to severe conditions of load, wear and chemical erosion of the surface. The nitrocarburizing and post-oxidation heat treatment, also known as quench-polish-quench (QPQ), improves the fatigue, wear and corrosion resistance properties of the material, since it increases the surface hardness and generates surface compressive residual stresses. In the present contribution, the effects of the salt bath nitrocarburizing and post-oxidation heat treatment on the static and fatigue behaviours of 39NiCrMo3 construction steel have been investigated by experimentally testing plain as well as notched specimens. For comparison purposes, 39NiCrMo3 construction steel, both untreated and treated, and X5CrNiCuNb 16-4 stainless steel have been tested. First, the microstructure of the untreated and treated steel has been identified by metallographic analysis, micro-hardness measurements have been collected and residual stresses profiles have been obtained by using the X-ray diffraction technique. Then, experimental static and fatigue tests have been performed. Finally, the fracture surfaces have been analysed to locate fatigue crack nucleation sites.

Despite the fact that ceramics and polymers have found numerous applications in several mechanical systems, metals and metallic alloys still remain the main materials family for manufacturing the bulk of parts and components of engineering assemblies. However, in cases of components that are serving as parts of a tribosystem, the application of surface modification techniques is required to ensure their unhampered function during operation. After a short introduction on fundamental aspects of tribology, this review article delves further into four representative case studies, where the inappropriate application of wear protection techniques has led to acceleration of the degradation of the quasi-protected metallic material. The first deals with the effects of the deficient lubrication of rolling bearings designed to function under oil lubrication conditions; the second is focused on the effects of overloading on sliding bearing surfaces, wear-protected via nitrocarburizing; the third concerns the application of welding techniques for producing hardfacing overlayers intended for the wear protection of heavily loaded, non-lubricated surfaces; the fourth deals with the degradation of thermal-sprayed ceramic coatings, commonly used as wear-resistant layers.

Summary. Currently in the repair and manufacture at the stage of recovery of steel parts, widely used special coatings formed by electrolytic effects on ferrous ions. This technique offers high performance, ease of implementation, low cost of technological equipment and materials used, as well as easy automation of the process. However, this method has several disadvantages: low fatigue strength of reconditioned parts, insufficiently strong grip of the iron coating to the substrate, particularly in alloy steels, insufficient wear resistance. For the purpose of increasing durability and wear resistance of parts, restored through electrochemical action, it is proposed to use chemical-heat treatment, consisting in the application of carbonitriding. Investigated the efficacy of different modes of carbonitriding in the highly carburizing paste-and their influence on the structure and properties of iron plating. It is established that the nitrocarburizing both low and high temperatures repeatedly (6-7.5 times) increases the microhardness of the coatings. The highest hardness is obtained by low-temperature carbonitriding with direct quenching in water. Conducting the carbonitriding process at low temperatures (650 °C), significantly increases the hardness of the iron coatings, increasing the limit of its fluidity, a and also greatly increases its endurance limit. Nitrocarburized fatigue strength of samples with iron precipitation on the surface, as shown by our studies, not only higher strength of the same samples without carbonitriding (more than 2 times), but higher than the fatigue strength of the base metal without coatings. Raising the temperature of the carbonitriding did not increase the hardness of electrolytic iron. Developed a rational technology of hardening of steel parts, re-chain iron fortification. Selected optimum conditions for carbonitriding hardening restored iron fortification, with the purpose of increasing durability of machine parts Optimal process temperature re-benching of the process of carbonitriding in which is possible to obtain maximum fatigue strength and wear resistance from the restored detail, is the process of carbonitriding at 650°C, followed by quenching and tempering at 150 °C.

In this study, electrolytic plasma processing (EPP) was employed for surface nitrocarburizing of AISI 1020 steel in a urea electrolyte, where the substrate samples were connected cathodically to a high-voltage DC current power supply. The structural, mechanical, wear and corrosion properties of the samples treated for 3–5 min were investigated. The results show that the surface layers formed on the samples by this treatment at 220 V have a ferritic nitrocarburizing characteristic which consists of a compound layer and diffusion zone. The surface layers of the treated samples at 240 V consisted of a compound layer, martensitic layer and diffusion zone, respectively, which is a marker of austenitic nitrocarburizing. The compound layers formed at 220 V and 240 V consisted of �-Fe2-3 (N,C) and � ′ -Fe4 (N,C) phases. The hardness value of the compound layer on the substrate was about 930 HV which was 4.5 times higher than that of the substrate. The thickness of the surface layer formed on the samples was a function of time and applied voltage. The wear and corrosion resistances of the samples were improved due to the surface treatment. © 2013 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier

Plasma electrolytic saturation (PES) is an atmospheric pressure plasma deposition which is used for fabrication of nanostructural coatings. This process starts with the appearance of some sparks on the surface and finally by the formation of plasma envelope around the sample, particles and free radicals bombard the surface and diffusion takes place into the work-piece. In this paper, the effect of frequency (500, 1000 and 10000 Hz) as pulse parameters on properties of nitrocarburized layers deposited on AISI 1045 steel were investigated. The analytical characteristics of the coating were assessed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The corrosion behavior of coatings was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% sodium chloride solution. Moreover, the microhardness and wear resistance of coated samples were also studied. The results indicated that applying nitrocarburized layer in all cases, improved the corrosion resistance, microhardness and also wear resistance of the substrate. The coatings treated at the frequency of 10000 Hz, had corrosion resistance about 2.4 and 1.4 times higher than those of the samples prepared at the frequency of 500 Hz and 1000 Hz. The surface hardness of 10000 Hz treated sample was about 1040 Vickers, which was more than those of the two other ones. An increase in frequency also caused wear resistance to increase.

Los tratamientos de nitruración se consideran preceptivos para aceros de alta aleación. Sin embargo, es práctica común la aplicación en aceros de baja aleación. Por otro lado, existen discrepancias en cuanto a las deformaciones producidas en piezas por dichos procesos. Atendiendo a lo anterior, el trabajo constó de dos partes experimentales diferenciadas. La primera parte del estudio consistió en una comparación de los efectos de tres procesos de nitruración industriales (baño de sales, gaseosa y por plasma) en las características de cuatro aceros: un acero al carbono; un acero de temple y revenido; un acero de herramientas; y un acero inoxidable. En todos los casos se realizó perfil de microdurezas y estudio metalográfico, con el fin de caracterizar las capas nitruradas. Las fases y durezas máximas obtenidas fueron las esperables para cada tipo de acero. En la estimación de la capa efectiva, se halló un cambio muy significativo de un proceso a otro. La segunda parte consistió en la estimación de las deformaciones producidas en tres tipos de piezas de geometrías críticas tras someterlas a los dos procesos de nitruración clásicos. Piezas fabricadas en dos tipos de acero, en tres estados estructurales diferentes. Se realizaron medidas de las dimensiones críticas, antes y después del tratamiento. Los resultados obtenidos mostraron que los procesos de nitruración provocan deformaciones de gran variabilidad en función del tipo de pieza, material, estado inicial y, sobre todo, proceso de nitruración. Las distorsiones alcanzaron hasta los 0,1 mm. La nitruración gaseosa provocó las más significativas Nitriding treatments are considered mandatory for high alloy steels. However, their application is a common industrial practice in lower alloyed steels. On the other hand, there are arguments about the rate of distortion that is generated in parts treated by such processes. The first part of the study is a comparison among three industrial nitriding processes (salt bath, gas and plasma) through their effects on the features of four types of steel: a carbon steel (C45E); a tempering steel (42CrMo4); a tool steel (X40CrMoV5-1); and a stainless steel (X20Cr13). In all cases, a microhardness profile and a metallographic study were performed in order to identify characteristic phases and estimate values of the effective layer. The maximum values of hardness obtained were as expected for each type of steel. During estimation of the effective layer, a significant difference among processes was found out. The second part of the study was made to estimate distortion within three types of parts after suffering two sorts of nitriding processes. Those were made of two kinds of steel (C45E and 42CrMo4), which were initially in three different structural states. Critical dimension measuring was made before and after treatment. Common measuring instruments, which are available in an industrial plant, were used. The results showed that nitriding processes cause highly variable deformation depending on the type of workpiece, material, initial state and, especially, the nitriding process. Distortion reached up to 0.1 mm. Gas nitriding caused the most significant strain. Máster Universitario en Ingeniería de Materiales y Fabricación por la Universidad Pública de Navarra Materialen eta Fabrikazioaren Ingeniaritzako Unibertsitate Masterra Nafarroako Unibertsitate Publikoan

This work is aimed to develop and optimize a gas ferritic oxynitrocarburizing treatment applied to an industrial 16MnCr5 component. The main effort has been to reduce the treatment time and the gas consumption by using a nitriding atmosphere that comprises nitrous oxide and ammonia. Special attention has been paid to improve the salt spray corrosion resistance with respect to the hardness requirements and the whole compound zone depth.

In this work the surface roughness behaviour in the forming of gaseous nitrocarburized layers has been analyzed. Ra values from 0.02 to 1.50 μm. has been considered. Obtained results prove a minor influence on layer thickness. A little increase of Ra has been observed. The abrasive wear resistance of nitrocarburized specimens was researched. The carbonitride ε is the only constituent in the about 6 μm thickness layers that have been carried out in this work. The tests revealed a minor wear resistance of the external part in the layers. This way, the external zone is less effective to wear phenomena than the internal. The specimens with small roughness parameters values show a higher poor wear resistance zone.En este trabajo se estudia la influencia que el acabado superficial del acero X40CrMoV5 1 tiene sobre la capa blanca o de combinación formada en el proceso de la nitrocarburación gaseosa. Se consideran acabados superficiales en el rango de 0,02 a 1,50 μm para Ra. Los resultados obtenidos indican que la rugosidad aumenta en todos los casos, aunque tiene poca influencia sobre el espesor de capa formada. También se ha investigado el comportamiento frente al desgaste abrasivo de las capas obtenidas que están constituidas en su totalidad por nitrocarburo ε y son de un espesor aproximado de 6 μm. Se ha encontrado un comportamiento diferenciado frente al desgaste de la zona externa de la capa frente a la zona subsuperficial. Los resultados revelan que la capa externa de la capa de combinación es poco efectiva frente al desgaste en relación con la capa subsuperficial. La zona de peor comportamiento es mayor para las probetas con acabados superficiales más finos.

Powder characteristics and manufacturing processes determine the microstructure, and therefore, the physical, chemical, and mechanical properties of sintered steels. In particular, porosity and corrosion resistance are intimately related, since the contact area between substrate and electrolyte significantly affects the corrosion resistance of sintered steels. This study addresses the effect of powder characteristics and pressing parameters on the microstructure and corrosion resistance of low-carbon sintered and sintered/plasma-nitrocarburized steel. The results indicated that the corrosion resistance increased with increasing density and decreasing specific surface area. Additionally, plasma-nitrocarburizing was highly effective in coating open pores of the material.

The present work shows the behaviour of low carbon alloyed steels as AISI-SAE 8615, after a ferritic nitrocarburizing process. Nitrocarburizing takes place at 570ºC for 3 h in an atmosphere by combustion of methanol and urea under different flow rates. Metallographic studies were performed by optical microscopy. Hardness profiles were measured and carbon percentages were also analized by emission spectrometry in order to determine the extension of the nitrocarburizing process. Optimal flow conditions have been found. The influence of the flow rate on the nitrocarburizing layer thickness has been also studied.El presente trabajo muestra el comportamiento del acero aleado de bajo contenido de carbono, AISISAE 8615, cuando se somete a un proceso de nitrocarburación ferrítica, a la temperatura de 570ºC y un tiempo de 3 h. La atmósfera reactiva ha sido generada mediante goteo variable de metanol y urea dentro del horno, utilizando distintas velocidades de flujo. Las capas nitrocarburadas fueron evaluadas mediante técnicas de microscopía óptica. Con el fin de conocer la extensión de las capas nitrocarburadas obtenidas, se realizaron medidas de microdureza y se determinaron los porcentajes de carbono en el proceso mediante espectroscopia de emisión. Se han encontrado las condiciones de flujo óptimo de la mezcla anteriormente comentada y se ha observado cómo su variación influye en el espesor de la capa nitrocarburada.

Made available in DSpace on 2022-04-29T07:26:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-01-01 The expanded austenite γN can be produced in austenitic stainless steels by plasma nitriding, carburizing or nitrocarburizing at low temperatures. This metastable phase presents higher hardness and toughness if compared with traditional nitride layers whilst also maintaining the corrosion resistance. However, the application of plasmas composed by both nitrogen and carbon is technologically recent and the effect of such process on the microstructure and properties of the nitrocarburized layers is still under investigation. In this study, samples of UNS S31254 superaustenitic stainless steel were produced by plasma nitriding and nitrocarburizing at 400 C, 450 C and 500 C for 5 h. The plasma treated samples were observed by optical and transmission electron microscopy and also analyzed by X-ray diffraction. The thickness of the layers increased with temperature and the nitrocarburized layers were thicker than nitrided at a given temperature. The presence of expanded austenite was confirmed by X-ray diffraction through its characteristic anomalous shift on the diffracted peaks related to the austenite. Nitride formation on samples produced at 400 C was only identified by transmission electron microscopy where fine rounded particles with 10-15 nm size revealed reflections consistent with the CrN cubic chromium nitride. The estimated lattice parameter from the expanded austenite ranged from 0.38 to 0.41 nm depending on the employed {h k l} reflection which was found to be 6-11% larger than the untreated austenite lattice parameter. © 2013 Brazilian Metallurgical, Materials and Mining Association. Department of Materials Engineering, Escola de Engenharia de São Carlos, Universidade de São Paulo (EESC/USP), São Carlos, SP Department of Mechanical Engineering, Universidade Estadual Paulista (UNESP), Ilha Solteira, SP Department of Mechanical Engineering, Universidade Estadual Paulista (UNESP), Ilha Solteira, SP

Досліджена в роботі нітроцементація із циклічним нагріванням має ряд переваг порівняно з нітроцементацією з ізотермічним нагріванням. Проведення такого процесу ХТЦО призводить до зменшенні його часу, здрібнення зерна і покращання механічних властивостей. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/30035 Исследованная в работе нитроцементация с циклическим нагревом имеет ряд преимуществ по сравнению с нитроцементацией с изотермическим нагревом. Проведение такого процесса ХТЦО приводит к уменьшению времени его прохождения, измельчению зерна и улучшению механических свойств. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/30035 The investigated in the paper nitrocarburizing with cyclic heating has several advantages compared with nitrocarburizing with isothermal heating. Carrying out of such chemical-thermocyclic treatment process leads to its time reduction, grain refinement and to improvement of the mechanical properties. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/30035

Nitrocarburizing is one of the frequently applied processes that significantly improve the service life of steel parts in the complex activity of mechanical loads, wear, and corrosion damages. Characterization and confirmation of the quality of a nitrided/nitrocarburized layer is a prescribed norm which includes the determination of surface hardness, nitriding hardening depth, compound zone thickness and its porosity. In the testing of surface hardness, in spite of determined conditions, there are additional factors that can affect the obtained result and can lead to a misunderstanding between the customer and the provider of the service of nitriding. In this paper, possible influential factors related to the surface hardness are considered and statistically analyzed by the ANOVA two factor test. The considered influential factors are: surface preparation method and loading force. Tests carried out during the research indicated a significant influence of the loading force and of the surface preparation on the results of the nitrided/nitrocarburized steel surface hardness. Also, the indentation size effect is confirmed in the hardness tests with a small loading force.

Improvement of wear and corrosion resistanceof ferrous alloys bypost-nitrocarburizing treatmentsR. Sola, R. Giovanardi, P. Veronesi, G. Poli

Different aspects of thermochemical treatments (nitriding, carburizing and nitrocarburizing) of austenitic stainless steel AISI 316 L conducted at low temperature were discussed. In the first chapter, a state of the art of these thermochemical treatments, as well as techniques used to achieve them have been presented. The nitriding and carburizing treatments, performed in a plasma reactor assisted by microwave in the Matrix Distributed Electron Cyclotron Resonance configuration, were studied in chapter 3. Analysis of the treated layers was performed by different experimental techniques: optical microscopy, profilometry, X-ray diffraction, Secondary Neutral Mass Spectroscopy, Secondary Ion Mass Spectrometry and glow discharge spectroscopy. In the fourth chapter, the nitrocarburizing treatment was studied and compared to sequenced carburization / nitriding and nitriding / carburizing treatments. A strong correlation was made between the average concentration of interstitial elements and the average compressive residual stress in the treated layers. The final chapter deals with the surface texturation or patterning to the nanometer or micrometer scale. To achieve this patterning, the deformation properties of the expanded austenite, formed during a nitriding treatment at low temperature, are used to construct a two dimensional array of dots, using grids or metallic tissues playing the role of masks to transfer a pattern on a piece of austenitic stainless steel; Différents aspects des traitements thermochimiques (nitruration, carburation et nitrocarburation) de l'acier inoxydable austénitique AISI 316 L menés à basse température ont été abordés. Dans le premier chapitre, un état de l'art de ces traitements thermochimiques, ainsi que des techniques mises en oeuvre pour les réaliser ont été présentés. Les traitements de nitruration et de carburation, réalisés dans un réacteur de plasma micro-ondes, dans la configuration Matrice à Résonance Cyclotronique Électronique Distribuée, ont été étudiés dans le chapitre 3. L'analyse des couches traitées a été effectuée par différentes technique expérimentales : microscope optique, profilométrie, diffraction des rayons X, spectrométrie de masse des neutres secondaires, spectrométrie de masse d'ions secondaires et spectroscopie à décharge luminescente. Dans le quatrième chapitre, le traitement de nitrocarburation a été étudié et comparé à des traitements séquencés carburation / nitruration et nitruration / carburation. Une corrélation très forte a été effectuée entre la concentration moyenne en éléments interstitiels et la contrainte résiduelle de compression moyenne dans les couches traitées. Le dernier chapitre traite de la texturation ou structuration de surface à l'échelle micrométrique ou nanométrique. Pour réaliser cette structuration de surface, les propriétés de déformation de l'austénite expansée, formée lors d'un traitement de nitruration à basse température, sont exploitées pour construire un réseau bidimensionnel de plots, à l'aide de grilles ou des tissus métalliques jouant le rôle de masques pour transférer un motif sur une pièce en acier inoxydable austénitique

Different aspects of thermochemical treatments (nitriding, carburizing and nitrocarburizing) of austenitic stainless steel AISI 316 L conducted at low temperature were discussed. In the first chapter, a state of the art of these thermochemical treatments, as well as techniques used to achieve them have been presented. The nitriding and carburizing treatments, performed in a plasma reactor assisted by microwave in the Matrix Distributed Electron Cyclotron Resonance configuration, were studied in chapter 3. Analysis of the treated layers was performed by different experimental techniques: optical microscopy, profilometry, X-ray diffraction, Secondary Neutral Mass Spectroscopy, Secondary Ion Mass Spectrometry and glow discharge spectroscopy. In the fourth chapter, the nitrocarburizing treatment was studied and compared to sequenced carburization / nitriding and nitriding / carburizing treatments. A strong correlation was made between the average concentration of interstitial elements and the average compressive residual stress in the treated layers. The final chapter deals with the surface texturation or patterning to the nanometer or micrometer scale. To achieve this patterning, the deformation properties of the expanded austenite, formed during a nitriding treatment at low temperature, are used to construct a two dimensional array of dots, using grids or metallic tissues playing the role of masks to transfer a pattern on a piece of austenitic stainless steel, Différents aspects des traitements thermochimiques (nitruration, carburation et nitrocarburation) de l'acier inoxydable austénitique AISI 316 L menés à basse température ont été abordés. Dans le premier chapitre, un état de l'art de ces traitements thermochimiques, ainsi que des techniques mises en oeuvre pour les réaliser ont été présentés. Les traitements de nitruration et de carburation, réalisés dans un réacteur de plasma micro-ondes, dans la configuration Matrice à Résonance Cyclotronique Électronique Distribuée, ont été étudiés dans le chapitre 3. L'analyse des couches traitées a été effectuée par différentes technique expérimentales : microscope optique, profilométrie, diffraction des rayons X, spectrométrie de masse des neutres secondaires, spectrométrie de masse d'ions secondaires et spectroscopie à décharge luminescente. Dans le quatrième chapitre, le traitement de nitrocarburation a été étudié et comparé à des traitements séquencés carburation / nitruration et nitruration / carburation. Une corrélation très forte a été effectuée entre la concentration moyenne en éléments interstitiels et la contrainte résiduelle de compression moyenne dans les couches traitées. Le dernier chapitre traite de la texturation ou structuration de surface à l'échelle micrométrique ou nanométrique. Pour réaliser cette structuration de surface, les propriétés de déformation de l'austénite expansée, formée lors d'un traitement de nitruration à basse température, sont exploitées pour construire un réseau bidimensionnel de plots, à l'aide de grilles ou des tissus métalliques jouant le rôle de masques pour transférer un motif sur une pièce en acier inoxydable austénitique

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:02:55Z No. of bitstreams: 1 S0370-44672010000100024.pdf: 293608 bytes, checksum: 22d9f87841b5e6590763815bc8ecbfc7 (MD5) Made available in DSpace on 2013-08-22T19:02:55Z (GMT). No. of bitstreams: 1 S0370-44672010000100024.pdf: 293608 bytes, checksum: 22d9f87841b5e6590763815bc8ecbfc7 (MD5) Previous issue date: 2010-03-01 Made available in DSpace on 2013-09-30T20:04:13Z (GMT). No. of bitstreams: 2 S0370-44672010000100024.pdf: 293608 bytes, checksum: 22d9f87841b5e6590763815bc8ecbfc7 (MD5) S0370-44672010000100024.pdf.txt: 11335 bytes, checksum: 333c8b82ba06bb09376d4049cf6b2b52 (MD5) Previous issue date: 2010-03-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:29:38Z No. of bitstreams: 2 S0370-44672010000100024.pdf: 293608 bytes, checksum: 22d9f87841b5e6590763815bc8ecbfc7 (MD5) S0370-44672010000100024.pdf.txt: 11335 bytes, checksum: 333c8b82ba06bb09376d4049cf6b2b52 (MD5) Made available in DSpace on 2014-05-20T13:29:38Z (GMT). No. of bitstreams: 2 S0370-44672010000100024.pdf: 293608 bytes, checksum: 22d9f87841b5e6590763815bc8ecbfc7 (MD5) S0370-44672010000100024.pdf.txt: 11335 bytes, checksum: 333c8b82ba06bb09376d4049cf6b2b52 (MD5) Previous issue date: 2010-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A dureza e, conseqüentemente, a resistência ao desgaste dos aços inoxidáveis austeníticos podem ser acentuadamente aumentadas, sem perdas na resistência à corrosão, com a produção de camadas superficiais pelo tratamento de nitrocementação por plasma. Nesse trabalho, foram nitrocementadas por plasma, na temperatura de 450°C, amostras do aço AISI 316L. As camadas obtidas foram caracterizadas por meio de ensaios micrográficos, de microdureza e de microdesgaste. A camada produzida constituiu-se de duas regiões, sendo a mais externa constituída de nitrocarbonetos de cromo e, abaixo dela, verificou-se a presença de austenita expandida, rica em nitrogênio, com dureza próxima a 850HV. A espessura média total da camada foi de, aproximadamente, 40µm. Sua resistência ao desgaste foi muito superior à do substrato. Hardness and consequently wear resistance of austenitic stainless steel can be highly increased, without losing corrosion resistance, by plasma nitrocarburizing surface treatment. In this re-search, an AISI 316L stainless steel was plasma nitrocarburized at 450°C, and the obtained layers were characterized by optical microscopy, microhardness and micro-wear tests. It was verified that the layer is composed of chromium nitrides precipitates and beneath them, a nitrogen rich expanded austenite, with hardness around 850HV. The total average thickness of the layer was about 40µm and presented good uniformity. The wear resistance of the layer was much higher than that of the substrate. USP Escola de Engenharia de São Carlos Aeroalccol UNESP Faculdade de Engenharia de Ilha Solteira USP Instituto de Química de São Carlos UNESP Faculdade de Engenharia de Ilha Solteira CNPq: 150799/2008-0

In order to improve mechanical properties, corrosion resistance, and wear resistance of steel grade EN C45, the surface of the steel was subjected to the thermochemical modification by salt bath nitrocarburizing, with or without post-oxidation. A marked improvement in the steel properties is noted especially after the formation of iron oxide layer on the compound zone during the cooling process after nitrocarburizing and even more during the subsequent treatment in the oxidizing bath. For the evaluation of the effect of post-oxidation parameters on the surface hardness and on the resistance to corrosion and wear, test samples were subjected to electrochemical corrosion investigations and adhesion wear tests. The obtained results confirm favourable effects of the post-oxidation of nitrocarburized layer on the resistance to adhesion wear and to electrochemical corrosion. The same effect was not observed in non-oxidized steel.

Gas nitrocarburizing and post-oxidation treatments were performed on 42CrMo4 steel and GS600 cast iron, to improve wear and corrosion resistance. In both materials the compounds layer after nitrocarburizing, mainly composed by ?-Fe2-3(N,C) and ?’- Fe4N phase. First the oxidizing step, a subsequent impregnation with two different lubricating oils was performed in order to further enhance corrosion resistance. Wear resistance was measured using a ball-on-disk tribometer with Al2O3 and 100Cr6 counterpart and the corrosion resistance of the samples was studied using salt spray test in accordance with ASTM B117 and electrochemical cell. Experimental results show that the nitrocarburizing treatment improves significantly the wear resistance of the steel but not the wear resistance of the studied cast irons. The application of nitrocarburizing alone does not significantly improve corrosion resistance and it may even promote localized corrosion. The subsequent postoxidation step leads to a slight decrease of the corrosion rate, because it partially seals the porous nitrocarburized layer. The final oil impregnation step resulted much more effective in further decreasing the corrosion rate by one order of magnitude.

The surface of the non-alloyed carbon steel was subjected to thermochemical modification by salt bath nitrocarburizing with or without postoxidation based on the Tenifer procedure in order to improve mechanical properties, corrosion and wear resistance. Nitrocarburized layers were characterized by testing their basic properties (compound layer thickness, nitrocarburizing depth, surface hardness) according to current standards. Detailed estimation of the quality of the modified metal surface was performed by additional testing of chemical compositions by EDX and X-ray diffraction, microstructure, surface roughness and topography, and corrosion resistance. The corrosion resistance was investigated in a water solution of 5% NaCl using electrochemical polarization methods and electrochemical impedance spectroscopy. The corrosion properties of the treated and nontreated samples are compared among themselves and with the properties of austenitic stainless steel. The surface layer obtained after nitrocarburization treatment consists mainly of e-Fe2–3N and γ′-Fe4N. The surface layer of the samples after post-oxidation consists also of e-Fe2–3N and γ′-Fe4N, but contains additionally Fe3O4. The results obtained show that nitrocarburizing and post-oxidation treatments, based on the Tenifer procedure, result in better mechanical and corrosion properties of non-alloyed carbon steel. The corrosion properties of the thermochemically modified non-alloyed carbon steel were improved and approach the corrosion properties of austenitic stainless steel, known for its very good corrosion resistance.

Tribological (wear resistance) and chemical (corrosion resistance) properties of carbon steel can be improved by application of thermochemical processes such as nitrocarburization and oxidation. One of the most popular processes of nitrocarburizing in a salt bath is TENIFER® ; ; ; QPQ with post-oxidation. In the TENIFER® ; ; ; QPQ process steel samples are subjected to nitrocarburization in a salt bath at 580 °C, cooling down to the temperature of 350°C in a hydroxide bath, followed by cooling to the room temperature. After this procedure, samples can be polished and oxidized once more. The described process causes changes only in the shallow surface layer of the carbon steel sample in which formation of iron nitrides and oxides can be observed. The aim of this work is to study the influence of each of these process steps on the corrosion resistance of carbon steel. Investigations are performed by means of the electrochemical measurements (polarization resistance determination, Tafel extrapolation method, EIS) in a 5% sodium chloride solution. Surface roughness and microstructure analysis are also examined. The distribution of nitrogen, carbon and oxygen are measured with EDS.

Plasma immersion ion implantation (PIII) has been employed for nitrocarburizing 304 stainless steel. The sample was treated at relativelylow gas pressure of nitrogen and acetylene in the range of 10 3 mbar. The microstructure variation, the austenite lattices spacing and thephase transformations were studied in-situ during heating up to 800 8C and after cooling, using synchrotron X-ray diffraction. Glowdischarge optical spectroscopy (GDOS), optical microscopy and hardness profile measurements have been used before and after thermaltreatment to analyse the nitrocarburized layer.D 2005 Elsevier B.V. All rights reserved. Keywords: Plasma immersion ion implantation (PIII); Synchrotron radiation; Continuous annealing; Microstructure; GDOS; Hardness profile 1. IntroductionStainless steel alloys are used for a large scale in today’stechnology and are entered in many applications. Manyplasma-based techniques have been used to improve themechanical and tribological properties of austenitic stainlesssteels. Radio frequency glow discharge (RFGD) has beenemployed for nitriding, nitrocarburizing and carbonitridingdifferent materials [1–5]. The plasma immersion ion implan-tation (PIII) has been widely used in the last 10 years as aresearchandindustrialmethodtocontrolsurfacetreatmentofstainless steels [6–8]. Overall, good corrosion resistance ismaintained while the wear resistance is increased [9,10].Frequently components like gears, axles and some engineparts need to be tough andductile but, at the same time, havea hard and good wear-resistant surface. These difficultcombinations of properties are achieved with stainless steeltreated by plasma nitriding, carbonitriding, nitrocarburizing,andcarburizing.Machinery,workingatelevatedtemperaturesuch as moving parts with relatively high friction, mightundergo phase transformation. Normally, these phase trans-formations reduce the lifetime of the components due to thedependence of the mechanical properties such as wearresistance, friction coefficient and the surface hardness onthe microstructure of the treated layer.The aim of this work is to study in-situ the thermal phasestability of 304 stainless steel treated by plasma immersionion implantation (PIII). Synchrotron X-ray diffraction,optical microscopy, microhardness, and glow dischargeoptical spectroscopy techniques have been used for theseinvestigations.2. Experimental2.1. PIII nitrocarburizingThe samples were cut from 1 mm thick 304 stainlesssteel sheet, into small pieces of order 10 mm 15 mm. Finemechanical polishing was used to decrease the surfaceroughness R

The comparative testing of properties for the steel grade Ck45 (AISI-1045) after salt bath nitrocarburizing (TENIFER process) without and with post-oxydation (TENIFER QPQ process) was performed. To evaluate the effects of post-oxidation on differently nitrocarburized specimens metallographic testing, investigation of chemical composition through the sample cross-section, testing of hardness, roughness, corrosion and tribological properties were carried out. The results indicate that post-oxidation has no significant effect on the hardness decrease, it lowers, however the friction coefficient and improve the corrosion resistance in comparison to the non-oxidized steel. That enhancement in properties is effect of the formation of iron oxide layer on the compound zone during the cooling after nitrocarburizing and especially during the subsequent treatment in the oxidizing bath.

Results of investigation of influence of post-oxidation of nitrocarburised carbon steel of case hardening class upon the improvement of resistance to wear and corrosion have been reported in the contribution. Oxidation of test samples has been conducted in the oxidizing AB1 bath, subsequent to the nitrocarburising in the TENIFER salt bath. Test pieces have been subjected to corrosion and tribological investigation. Corrosion testing has been done applying electrochemical methods, while trobological testing included investigation of resistance to adhesion. The obtained results indicate favorable effects of post-oxidation of nitrocarburised layer upon both, resistance to adhesion wear and corrosion.

SICAK İŞ TAKIM ÇELİKLERİNİN NITROKARBURIZASYON İŞLEMİNE PROPANIN ETKİSİ Ömer ÇİMEN Anahtar Kelimeler : Nitrokarbürizasyon, Sıcak iş takım çelikleri, Sertleştirme Özet : Nitrokarbürizasyon, atomik azot ile birlikte ortama propan ilave edilerek, azotun önce çelik yüzeyine ve oradan da yayınmayla yüzey altına taşınmasıyla gerçekleşen bir yüzey sertleştirme işlemidir. Bu yöntemle, endüstride özellikle dövme, ekstrüzyon ve enjeksiyon döküm sektöründe yaygın olarak kullanılan sıcak iş takım çeliUerinin yüzeyleri kaplandığı taktirde, maliyetleri oldukça yüksek olan takım ve kalıpların aşınma, yorulma ömürleri ile oksidasyon ve korozyon gibi dış etkenlere karşı dayanımları artacaktır. Dolayısıyla ekonomiye büyük faydalar sağlayacak verimlilik kriterleri elde edilecektir. Bu çalışmada, sertleştirme hakkında genel bilgiler, sıcak iş takım çeliklerinin sertleştirilmesi ve değişik karbonitrürleme işlemleri uygulamalarıyla beraber sunuldu. Deneysel çalışmalarda AISI H13 çeliğinin yüzey sertleştirme özellikleri ile değişen propan gazı etkisi altında nitrokarbürizasyon işlemlerinin sonuçlan araştırıldı. İlk bölümde esas olarak nitrokarbürizasyon işlemine tabi tutulmuş yapıların mekanik ve elektrokimyasal avantajları sertleştirilmiş yapılara göre karşılaştırıldı. Kullanılan malzemenin özellikleri ve nitrokarbürizasyon işlemleriyle ilgili detay açıklamalar deneysel çalışmalar bölümünde verildi ve sonuç kısmında deneysel çalışmalardan elde edilen veriler tartışıldı. 11 THE INFLUENCE OF PROPANE ON THE NITROCARBURISING OF HOTWORK TOOL STEELS Ömer ÇİMEN Keywords : Nitrocarburising, Cold work tool steels, Hardening Abstract : Nitrocarburising is a surface hardening process realised by the transport of nitrogen to the steel surface and then below the surface by diffusion, with the help of propane. If the surface of hot work tool steels, especially widely used in forging, extrusion and injection casting industries, is coated with this method; the wear and fatigue life of high cost tools and dies will improve as well as the endurance against external conditions like oxidation and corrosion. Thus, efficiency criteria that will supply high profits to the economy will be obtained. In this study, general information about hardening, the hardening of hotwork tool steels and different carbonitriding processes along with applications are presented. In the experimental studies conducted, the surface hardening properties and the results of nitrocarburising processes under the influence of variable propane gas of AISI HI 3 steel is investigated. Basicly, the mechanic and electrochemical advantages of nitrocarburised structures against hardened ones are compared in the first section. The properties of the material used and detailed explanations about the nitrocarburising processes are given in the experimental studies section and the data obtained from the experimental studies are discussed in the conclusion section. in 107

NİTROKARBURASYON Pınar SEÇMEN Anahtar Kelimeler: Aşınma direnci, Deformasyon, Sertlik. Özet: Nitrokarbürasyon, parçaların aşınma direncini artırmak için kullanılan, parçanın daha yumuşak, kalın iç kısmının bundan etkilenmediği geniş bir teknikler bileşimini içerir. Tipik olarak, nitrokarbürasyon, düşük bir sıcaklıkta diğer yöntemlere göre daha kısa zamanda yapılır ve genelde daha sığ bir kaplama gerçekleştirilir. Nitrokarbürasyonda, diğerlerine göre kısmi deformasyon daha az olur ve boyutsal kontrol daha iyi olur. CARBONITRIDING Pınar SEÇMEN Keywords: Wear Resistance, Distortion, Hardness. Abstract: Carbonitriding, a surface hardening process which includes a wide variety of techniques, is used to improve the wear resistance of parts without affecting the where soft, tough interior of part. Typically, carbonitriding is carried out at a lower temperature and for a shorter time than is other methods, producing a shallower case than is usual in production other methods. Carbonitriding may produce less part distortion and better control of dimensions than others. 11 52

The present work shows the behaviour of low carbon alloyed steels as AISI-SAE 8615, after a ferritic nitrocarburizing process. Nitrocarburizing takes place at 570ºC for 3 h in an atmosphere by combustion of methanol and urea under different flow rates. Metallographic studies were performed by optical microscopy. Hardness profiles were measured and carbon percentages were also analized by emission spectrometry in order to determine the extension of the nitrocarburizing process. Optimal flow conditions have been found. The influence of the flow rate on the nitrocarburizing layer thickness has been also studied. El presente trabajo muestra el comportamiento del acero aleado de bajo contenido de carbono, AISISAE 8615, cuando se somete a un proceso de nitrocarburación ferrítica, a la temperatura de 570ºC y un tiempo de 3 h. La atmósfera reactiva ha sido generada mediante goteo variable de metanol y urea dentro del horno, utilizando distintas velocidades de flujo. Las capas nitrocarburadas fueron evaluadas mediante técnicas de microscopía óptica. Con el fin de conocer la extensión de las capas nitrocarburadas obtenidas, se realizaron medidas de microdureza y se determinaron los porcentajes de carbono en el proceso mediante espectroscopia de emisión. Se han encontrado las condiciones de flujo óptimo de la mezcla anteriormente comentada y se ha observado cómo su variación influye en el espesor de la capa nitrocarburada.